United States
Environmental Protection
     EPA 231K13001
       June 2013
    Our  Built and Natural Environments:
            A Technical Review of the Interactions Among Land Use,
                 Transportation, and Environmental Quality
                           SECOND EDITION
Office of Sustainable Communities
Smart Growth Program

The U.S. Environmental Protection Agency (EPA), through its Office of Sustainable Communities
managed the preparation of this report. This report has been subjected to the Agency's peer and
administrative review and has been approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute endorsement or recommendation for use.

Principal author: Melissa G. Kramer, Ph.D.

Contributors and reviewers from the U.S. Environmental Protection Agency:
•   Office of Sustainable Communities: Danielle Arigoni, Ted Cochin, John Frece, Susan Gitlin, Jeff Jamawat, Adam
    Klinger, Megan McConville, Kevin Nelson, Kevin Ramsey, Megan Susman, John Thomas, Tim Torma, Brett Van
    Akkeren, and Beth Zgoda
•   Office of Air and Radiation: Ken Adler, Stacy Angel, Chad Bailey, Laura Berry, Gregory Brunner, James Hemby,
    Rudy Kapichak, Jean Lupinacci, Neelam Patel, Meg Patulski, Karl Pepple, Tamara Saltman, Erika Sasser, Kimber
    Scavo, and Mark Simons
•   Office of Chemical Safety and Pollution Prevention: Matt Bogoshian, David Sarokin, and Tom Simons
•   Office of Environmental Justice: Suzi Ruhl
•   Office of Policy: Alex Barron
•   Office of Research and Development: Fran Kremer, Melissa McCullough, Joseph McDonald, and Barbara
•   Office of Solid Waste and Emergency Response: Ksenija Janjic and Patricia Overmeyer
•   Office of Water: Laura Bachle, Veronica Blette, Robert Goo, Rachel Herbert, Christopher Kloss, and Jennifer
•   Region 5, Land and Chemicals Division: Bradley Grams

Other federal government reviewers:
•   Centers for Disease Control and Prevention: Lorraine Backer, Ginger Chew, Daneen Farrow-Collier, Robynn
    Leidig, Erin Sauber-Schatz, Arthur Wendel, and Margalit Younger
•   U.S. Department of Transportation: Alexandra Tyson
•   General Services Administration:  Ken Sandier
•   National Oceanic and Atmospheric Administration: Sarah van der Schalie
External peer reviewers:
•   Alexander Felson, Yale University
•   Susan Handy, University of California Davis
•   John Jacob, Texas A&M University
•   Kevin Krizek, University of Colorado
•   Dowell Myers, University of Southern California
Daniel Rodriguez, University of North Carolina
Frank Southworth, Georgia Institute of
Paul Sutton, University of Denver
Cover photo credits:
•   Front cover, top left: drouu via stock.xchng
•   Front cover, top right: Kyle Gradinger via flickr.com
•   Back cover, top right: Dan Burden via Pedestrian and Bicycle Information Center
•   All others: EPA

Table of Contents
Executive Summary	i
Chapter 1.    Introduction	1
  1.1    Purpose	1
  1.2    The Effects of the Built Environment on Human Health and the Natural Environment	2
     1.2.1    Direct Effects	2
     1.2.2    Indirect Effects	3
  1.3    Overview of Document	3
Chapter 2.    Status of and Trends in Land Use, Buildings, and Travel Behavior	5
  2.1    Status of and Trends in Population and Developed Land	6
     2.1.1    Population	6
     2.1.2    Metropolitan Area Size	7
     2.1.3    Developed Land	10
  2.2    Status of and Trends in Buildings	12
     2.2.1    Housing Units	12
     2.2.2    Building Energy Use	14
     2.2.3    Building Water Use	16
     2.2.4    Building Construction Waste Production	19
  2.3    Status of and Trends in Infrastructure	20
     2.3.1    Roads	20
     2.3.2    Parking	21
     2.3.3    Water, Wastewater, Utilities, and Other Infrastructure	22
  2.4    Status of and Trends in Impervious Cover	23
  2.5    Status of and Trends in Travel Behavior	25
     2.5.1    Vehicle Travel	26
     2.5.2    Induced Travel	27
     2.5.3    Transit, Walking, and Bicycling	29
  2.6    Future Trends	31
     2.6.1    Projected  Population Growth	31
     2.6.2    Projected  Land Conversion	32
     2.6.3    Projected  Changes in Development Trends	32
  2.7    Summary	33
Chapter 3.    Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel	34
  3.1    Habitat Loss, Degradation, and Fragmentation	34
     3.1.1    Effects of  Habitat Loss	35
     3.1.2    Effects of  Habitat Degradation	38
     3.1.3    Effects of  Habitat Fragmentation	41
     3.1.4    Effects of  Roads: Combined Effects of Habitat Loss, Degradation,  and Fragmentation.... 43
  3.2    Land Contamination	44
  3.3    Degradation and Loss of Water Resources	46
     3.3.1    Effects of  Development on Stream Hydrology	48

    3.3.2    Effects of Development on Stream Geomorphology	49
    3.3.3    Effects of Development on Water Pollution and Nutrients	51
    3.3.4    Effects of Development on Aquatic Life	54
    3.3.5    Levels of Development at Which Effects Are Apparent	55
    3.3.6    Loss of Water Resources	56
  3.4    Degradation of Air Quality	57
    3.4.1    Criteria Air Pollutants	57
    3.4.2    Air Toxics	59
    3.4.3    Human Health and Environmental Effects of Air Pollution	60
    3.4.4    Indoor Sources of Pollution	61
  3.5    Heat Island Effect	65
  3.6    Greenhouse Gas Emissions and Global Climate Change	65
    3.6.1    Greenhouse Gas Emissions Sources	66
    3.6.2    Effects of Global Climate Change	68
  3.7    Other Health and Safety Effects	70
    3.7.1    Activity Levels, Obesity, and Chronic Disease	70
    3.7.2    Emotional Health and Community Engagement	72
    3.7.3    Vehicle Crashes	73
  3.8    Summary	75
Chapter 4.    Effects of Different Types of Development on the Environment	76
  4.1    Where We Build	78
    4.1.1    Importance of Safeguarding Sensitive Areas	78
    4.1.2    Importance of Infill Development	80
    4.1.3    Benefits of Focusing Development Around Transit Stations	83
  4.2    How We Build	85
    4.2.1    Compact Development	87
    4.2.2    Mixed-Use Development	94
    4.2.3    Street Connectivity	97
    4.2.4    Community Design	99
    4.2.5    Destination Accessibility	102
    4.2.6    Transit Availability	103
    4.2.7    Green Building	105
  4.3    Scenario Planning	113
  4.4    Summary	117
Chapters.    Conclusion	118
Works Cited	120

Executive Summary
Decisions about how and where we build our communities have significant impacts on the natural
environment and on human health. Cities, regions, states, and the private sector need information
about the environmental effects of their land use and transportation decisions to mitigate growth-
related environmental impacts and to improve community quality of life and human health.

This report:

   •   Discusses the status of and trends in land use, development, and transportation and their
       environmental implications.

   •   Articulates the current understanding of the relationship between the built environment and
       the quality of air, water, land resources, habitat, and human health.

   •   Provides evidence that certain kinds of land use and transportation strategies can reduce the
       environmental and human health impacts of development.

Patterns of development, transportation infrastructure, and building location and design—the built
environment—directly affect the natural environment. Development takes the place of natural
ecosystems and fragments habitat. It also influences decisions people make about how to get around
and determines how much people must travel to meet daily needs. These mobility and travel decisions
have indirect effects on human health and the natural environment by affecting air and water pollution
levels, the global climate, levels of physical activity and community engagement, and the number and
severity of vehicle crashes.

Trends in land use, building patterns, and travel behavior highlight how significantly our development
patterns have changed in recent decades. The size of virtually every major metropolitan area in the
United States has expanded dramatically. In many places, the rate of land development has far outpaced
the rate of population growth, although more recent trends in some areas suggest the pattern could be
changing. As the amount of developed land has increased and more and larger homes have been built,
buildings, roads, and associated impervious surfaces have grown to serve an  increasingly dispersed
population. As our communities changed to accommodate cars, the percentages of people taking public
transit, walking, and biking declined. Projected population growth and demographic trends suggest that
the need for additional development will continue to increase.

As the U.S. population has grown, we have developed land that serves important ecological functions at
a significant cost to the environment. Development has destroyed, degraded, and fragmented habitat.
Water quality has declined. Air quality in many areas of the country is still adversely affecting human
health. The heat island effect and global climate change illustrate just how complex and far-reaching the
impacts of our built environment are. Community design can make it difficult for people to get adequate

Executive Summary
physical activity, engage with neighbors, and participate in community events. It can also increase the
risk of injury or death from a vehicle crash.

Changing where and how we build our communities can help mitigate these impacts, improving how
development affects the environment and human health:

    •   Where we build involves locating development in a region or land area. It includes safeguarding
       sensitive areas such as riparian buffers, wetlands, and critical habitat from development
       pressures; directing new development to infill, brownfield, and greyfield sites to take advantage
       of existing infrastructure and preserve green space; and putting homes, workplaces, and
       services close to each other in convenient, accessible locations.

    •   How we build includes developing more compactly to preserve open spaces and water quality;
       mixing uses to reduce travel distances; designing communities and streets to promote walking
       and biking; and  improving building design, construction, and materials selection to use natural
       resources more efficiently and improve buildings' environmental performance.

These elements are interrelated and often work most effectively in combination with each other rather
than individually. Although findings might differ on the magnitude of the effects of different practices,
the evidence is overwhelming that some types of development yield better environmental results than
others. Used in combination, these practices can significantly reduce impacts on habitat, ecosystems,
and watersheds and can reduce vehicle travel and energy use, which in turn reduces emissions that
cause local, regional, and global air quality concerns. As communities nationwide look for ways to
reduce the environmental and human health impacts of their development decisions, the evidence is
clear that our nation can continue to grow and can build a strong foundation for lasting prosperity while
also protecting our environment and health.

Chapter 1.  Introduction
1.1   Purpose

Recognition is increasing that land use and transportation decisions can either support or interfere with
environmental protection and quality of life. Policy-makers have realized that decisions about how and
where we build our communities have significant impacts on the natural environment. Cities, regions,
states, and the private sector are planning and implementing smart growth strategies and other
measures to mitigate growth-related environmental impacts and to improve community quality of life
and human health (Exhibit 1-1).
                                           Exhibit 1-1: Smart Growth. Smart growth strategies
                                           create sustainable communities by siting development in
                                           convenient locations and designing it to be more efficient
                                           and environmentally responsible. Communities across
                                           the country are using creative strategies to develop in
                                           ways that preserve natural lands and critical
                                           environmental areas, protect water and air quality, and
                                           reuse already-developed land. They conserve resources
                                           by reinvesting in existing infrastructure and reclaiming
                                           historic buildings. By designing neighborhoods that have
                                           shops, offices, schools, churches, parks, and other
                                           amenities near homes, communities are giving their
                                           residents and visitors the option of walking, bicycling,
                                           taking public transportation, or driving as they go about
                                           their business. A range of different types of homes makes
                                           it possible for senior citizens to stay in their homes as
                                           they age, young people to afford their first home, and
                                           families at all stages in-between to find a safe, attractive
                                           home they can afford. Through smart growth  approaches
                                           that  enhance neighborhoods and involve local residents
                                           in development decisions, these communities are
                                           creating vibrant places to live, work, and play. The high
                                           quality of life in these communities makes them
                                           economically competitive, creates business
                                           opportunities, and improves the local tax base.
This edition of Our Built and Natural
Environments updates the original 2001
publication with the most current
information available as of October
2012.1 It is written for everyone
interested in how land use practices,
transportation infrastructure, and
building siting and design directly and
indirectly  affect environmental quality.

This report provides information that can
help state and local governments decide
how to accommodate expected
population growth within their borders in
the most environmentally responsible
manner. Different parts of the country
face different challenges and
opportunities based on the availability of
fresh water, the mix of fossil fuel and
renewable energy sources, and their
vulnerability to natural  disasters, among other issues. Whether or to what extent growth should occur in
a particular region is beyond the scope of this document.
1 This paper generally uses the most recent literature. Studies older than 2005 are included only if they made an
important finding that is not repeated in later research. The document cites review articles when they are available
rather than individual studies to make the paper more concise. The document relies primarily on peer-reviewed
academic literature, reports by the National Academy of Sciences, and government publications that report on
government-collected data. Reports published by nonprofit organizations and private contractors are not included
because of uncertainty about the level of peer review and potential perceived bias.

This report also does not discuss the economic impacts of different land use, development, or
transportation decisions. The economic implications of various choices influence community decision-
making, and rightly so. However, this document focuses on how different choices can help protect
human health and the environment. EPA has published other reports that discuss some of the ways
certain types of development can provide better economic outcomes for businesses, local governments,
and households while also protecting the environment and improving quality of life.2

This report concludes that the built environment and the travel decisions it encourages have significant
impacts on the environment, human health, and community quality of life. As a result, it is important for
EPA; other federal, state, and local government agencies; real estate developers and investors; and
communities across America to understand the relationship between the built and  natural

1.2    The Effects of the Built Environment on Human Health and the Natural

For decades, people have recognized the environmental impacts resulting from industrial pollution. The
environmental effects of land use decisions are not as widely understood in spite of their tremendous
impact. Patterns of development, transportation infrastructure, and building location and design—the
built environment—directly affect the natural environment. Development takes the place of natural
ecosystems and fragments habitat.  It also influences decisions people make about how to get around
and determines how much people must travel to meet daily needs. These mobility and travel decisions
have indirect effects on human health and the  natural environment by affecting air and water pollution
levels, the global climate, levels of physical activity and community engagement, and the number and
severity of vehicle crashes (Exhibit 1-2).

1.2.1  Direct Effects

The extent of land development, the type of development, and the location of infrastructure have direct
and long-lasting impacts on ecosystems. Natural ecosystems serve a variety of functions that provide
people with necessary and valuable goods and  services. For example, natural  ecosystems maintain
healthy air quality, regulate temperature and precipitation, prevent flooding,  provide clean water for
drinking and industrial use, maintain healthy and productive soil, pollinate wild plants and crops,
maintain biological and genetic diversity, provide renewable natural resources, treat organic waste,
control pests and diseases, and provide recreation areas.3 Land development  often replaces natural
areas and damages or destroys many of these ecosystem functions and services. Land  development also
frequently affects  the amount and quality of essential habitat for plants and animals.
2 EPA's Office of Sustainable Communities has a variety of resources on the economic impacts of smart growth
strategies. See the Business and Economic Development section of the office's publications page:
3 de Groot, Wilson, and Boumans 2002

                     Built Environment
                        Land use patterns
                    Transportation infrastructure
                     Building siting and design
            Direct Effects
Mobility and Travel Decisions
    Car trip frequency and length
    Walking, biking, and transit use
                                 Indirect Effects
      Human Health and the Natural Environment
            Ecosystems, habitat, and endangered species
                       Water quality
                        Air quality
                       Global climate
                      Physical activity
            Emotional health and community engagement
                      Vehicle crashes
  Exhibit 1-2: Direct and indirect effects of the built environment.
                                                                   1.2.2   Indirect Effects

                                                                   How we develop land
                                                                   determines the distribution of
                                                                   jobs, housing, and community
                                                                   activities, which in turn
                                                                   determines how far people
                                                                   travel to meet their daily needs
                                                                   and their transportation
                                                                   options. These travel decisions
                                                                   affect air pollutant and
                                                                   greenhouse gas emissions and
                                                                   levels of physical activity. Land
                                                                   development patterns can
                                                                   disproportionately affect
                                                                   children, the elderly, and people
                                                                   with disabilities—groups that
                                                                   can be especially vulnerable to
the health effects of pollution. In addition, these groups, as well as racial and ethnic minorities  and
people of lower socioeconomic status, often have fewer options for where to live and work.4'5

Travel behavior is thus one of the most important indirect effects of how and where we build and is a
topic of intense investigation. Travel behavior is complex, with various factors simultaneously affecting
decisions about how much, where, when, and how to get around. Although the magnitude of the effect
is widely debated, a large body of evidence shows that community design affects travel behavior.
Moreover, the effect is large enough that changes in community design could help mitigate a range of
transportation, air quality, human health, and greenhouse gas problems.

1.3    Overview of Document

Chapter 2 covers current status of and trends in land use and travel behavior—how our population  has
grown; how we have developed land and constructed buildings and roads to accommodate growth; how
our use of cars has grown; and how transit use, walking, and biking have changed over time.

Chapter 3 looks at how these trends in land use and transportation have affected the environment,
including habitat loss, degradation, and fragmentation;  degradation of water resources and water
quality; degradation of air quality; and global climate change. Chapter 3  also considers the human health
 Younger, et al. 2008
5 EPA supports environmental justice, the fair treatment and meaningful involvement of all people regardless of
race, color, national origin, or income with respect to the development, implementation, and enforcement of
environmental laws, regulations, and policies. Consideration of how our development patterns affect
disadvantaged and vulnerable populations helps EPA achieve this goal. See: www.epa.gov/environmentaljustice.

effects of our built environment, including impacts on activity levels, obesity, chronic disease, level of
community engagement, and risk of injury or death from vehicle crashes.

Chapter 4 provides evidence that some patterns of growth and development can have better
environmental outcomes than others. Chapter 4 first covers the importance of where we build—how
safeguarding sensitive areas and focusing development on already-developed land and around transit
stations limits environmental impacts. The chapter then covers the importance of how we build, looking
at different patterns and practices that research indicates are better for the environment, including:

    •   Compact development.
    •   Mixed-use development.
    •   Street connectivity.
    •   Community design to support walking and biking.
    •   Development that improves access to destinations and transit.
    •   Green building.

Finally, Chapter 4 discusses studies that have looked at the combined effects of a range of tools that
improve the environmental outcomes of development.

The document concludes by summarizing the effects of how and where we build on efforts to achieve
national environmental goals.

Chapter 2. Status of and Trends in Land Use, Buildings, and Travel
The physical layout and design of our cities and towns have changed dramatically over the past century.
In the early 1900s, most urban areas had a compact central business district. Industrial facilities, ports,
rail terminals, and other infrastructure hubs anchored major employment centers. Residential areas had
small shops and businesses. Suburbs in the first half of the 20th century grew in tandem with extensions
of streetcar and railroad lines. They developed in the pattern of the downtown area, on a gridded street
network. Each new community typically extended only as far from streetcar lines as people might
comfortably walk.

This pattern for cities and towns began to change after World  War II, when the United States underwent
a period of great economic growth. The  expansion of the automobile industry as a key sector of the
nation's economy, the launch of the federal interstate highway construction  program in 1956, and
federal housing policies that encouraged home ownership fundamentally changed the nature of
development.6 The interstate system connected distant locations while also opening up rural areas for
development. Metropolitan areas now have multiple clusters of development widely dispersed.
Residential, commercial, and industrial uses are separated from each other, often due to local zoning
requirements. Many housing subdivisions are located far from stores and services, and if they have
sidewalks at all, the sidewalks typically connect only to other homes rather than to places people work,
shop, or go to school, making a car essential to daily life. Some business parks are so large that workers
need a car to get around inside the  park. Shopping malls and strip centers surrounded by large parking
lots have replaced many traditional downtown business districts.  Street networks are designed to send
most traffic to a few large arterial roads. As these changes occurred, people and  businesses moved
farther from central business districts, while the poor, many of them minorities, were often left behind
in communities suffering from disinvestment, where they found it increasingly difficult to access jobs,
services, and amenities.7

More recently, many city and town  centers have revitalized as new people and businesses have moved
to these areas for their historic architecture, walkable neighborhoods, and lively street life. As many of
the neighborhoods developed before World War II near city centers and along old streetcar lines are
being redeveloped, new developments are also starting to adopt  designs that appeal to people looking
for communities where they can live close to where they work, shop, and take care of other daily needs.

Despite these recent trends, a dispersed pattern of development  in the United States dominated during
a time in which the population grew significantly. Both population growth and development patterns
have contributed to the environmental impacts of our built environment. Development patterns to
' Vicino 2008
 Vicino 2008

Status and Trends in Land Use, Buildings, and Travel Behavior
accommodate additional population growth in the coming decades will help determine whether these
environmental impacts continue to worsen or begin to improve.

This chapter looks at trends in the following areas:

    1.   Population growth and developed land.
    2.   Buildings and their water, energy, and materials use.
    3.   Transportation infrastructure, including roads and parking.
    4.   Impervious cover.
    5.   Projected population growth and land conversion.

2.1    Status of and Trends in Population and Developed Land

2.1.1   Population

The population of the United States grew from 76,212,168 in 1900s to 311,591,917 in 2011.9 Most of the
population growth occurred in census-defined  urban areas, while the rural population remained
relatively constant (Exhibit 2-1). In 1900, just 40 percent of the population lived in urban areas; in 2010,
more than 80 percent did.







I Rural
                     1900  1910  1920 1930 1940 1950  1960  1970  1980  1990 2000 2010
           Exhibit 2-1: United States population, 1900-2010. The urban population includes those in
           urbanized areas of 50,000 or more people and those in urban clusters of at least 2,500 and fewer
           than 50,000 people. The U.S. Census Bureau does not define suburban population. However, most
           suburban communities fall under the Census definition of urban population. The rural population
           includes everyone not in an urban area.
           Sources: U.S. Census Bureau 1990 Census of Population and Housing 1993 and 2010 Census Urban
           and Rural Classification and Urban Area Criteria 2010.
' U.S. Census Bureau, POP Culture: 1900 n.d.
' U.S. Census Bureau, State & County QuickFacts n.d.

                                            Status and Trends in Land Use, Buildings, and Travel Behavior
2.1.2  Metropolitan Area Size

Although the population has grown dramatically in census-defined urban areas, the trend has largely
resulted in growth in suburbs rather than in central cities. The proportion of the population residing in
the suburbs grew from 23 percent  in 1950 to 47 percent in 2010, while the proportion residing in central
cities remained relatively constant.10 A literature review by the National  Research Council shows that
along with population, employment has shifted out of the central city areas. The combined effect is
more spread-out development that makes alternatives to driving (such as transit) less practical.11 In fact,
one of the most dramatic trends in the built environment has been the expansion in the geographic size
of metropolitan regions. Virtually every metropolitan region in the United States has expanded
substantially in land area since 1950.

Since 1950, the U.S. Census has defined  urbanized areas to better delineate urban places from rural
areas near larger cities. They are determined without regard to political boundaries to better reflect
actual settlement patterns. The U.S. Census has modified the definition with each census to ensure that
it continues to differentiate in a meaningful way between urban and rural populations. Nevertheless,
the U.S. Census has consistently based its definition of urbanized area on a population of at least 50,000
people that are part of a single area primarily based on population density.12 Exhibit 2-2 shows the
population growth and urbanized land area growth between 1950 and 2010 for 39 urbanized areas with
populations greater than 1,000,000 in 2010 that were delineated areas in 1950.

For all 39 areas combined,  urbanized area increased 2.5 times faster than population growth between
1950 and 2010. This overall trend reflects the fact that urbanized land area in most cities grew at a  much
faster rate than its population. In urbanized areas that lost population, the contrast between population
growth and urbanized area growth is especially remarkable.  Eight of the  top 15 cities in terms of the
ratio of area growth to population  growth shown in Exhibit 2-2 had population declines between 1970
and 1980 or between 1980 and 1990: Pittsburgh, Milwaukee, Detroit, St. Louis, Cleveland, New York,
Chicago, and Kansas City. In every case, urbanized land area continued to grow during the same period.
For example, in 1950, 0.1 acre of land was developed for each resident of the Pittsburgh metropolitan
region. At the peak of the region's  population in 1970, twice as much land was developed (0.2 acre) for
each resident.  As population declined, the region continued to expand—by 2010, three times the land
was developed for every resident compared to 60 years earlier. Exhibit 2-3 shows how the growth in the
metropolitan region's land  area continued despite population declines.

However, cities show considerable variation. While the urbanized area of many older, industrial cities
such as Pittsburgh,  Boston, Milwaukee, Philadelphia, Detroit, St. Louis, and Cleveland grew at a rate
more than five times the population growth rate, a minority of cities had population and urbanized area
growth trends  opposite those of the rest of the country. In these cities, the population growth rate
between  1950 and 2010 exceeded  the land area growth rate (see Exhibit 2-2). In Los Angeles and San
10 Short 2012
  National Research Council of the National Academies, Driving and the Built Environment 2009
12 U.S. Census Bureau, "Notice of final program criteria" 2011

Status and Trends in Land Use, Buildings, and Travel Behavior
Urbanized Area
Pittsburgh, PA
Boston, MA-NH-RI
Milwaukee, Wl
Philadelphia, PA-NJ-DE-MD
Detroit, Ml
St. Louis, MO-IL
Cleveland, OH
Cincinnati, OH-KY-IN
Baltimore, MD
New York-Newark, NY-NJ-CT
Indianapolis, IN
Chicago, IL-IN
Columbus, OH
Atlanta, GA
Kansas City, MO-KS
Jacksonville, FL
Providence, RI-MA
Charlotte, NC-SC
Washington, DC-VA-MD
Memphis, TN-MS-AR
Minneapolis-St. Paul, MN-WI
San Antonio, TX
Seattle, WA
Tampa-St. Petersburg, FL
Austin, TX
Sacramento, CA
Denver-Aurora, CO
Portland, OR-WA
Dallas-Fort Worth-Arlington, TX
San Francisco-Oakland, CA
Phoenix-Mesa, AZ
Orlando, FL
Miami, FL
Houston, TX
San Diego, CA
Salt Lake City-West Valley City, UT
Riverside-San Bernardino, CA
Los Angeles-Long Beach-Anaheim, CA
San Jose, CA
Land Area
2010 (mi2)
Ratio of Area
Growth to
Exhibit 2-2: Population growth and land area growth for urbanized areas, 1950-2010. The name of the urbanized area
identifies the major place(s) in the urbanized area and the state(s) in which the urbanized area is located.
Sources: U.S. Census Bureau 1961 (Table 22) and Changes in Urbanized Areas from 2000 to 2010 2010

Jose, the population growth rate was more than twice the land area growth rate. Cities showing this
pattern tend to be newer cities in the Sunbelt with a steadily increasing population.

If population and land area growth for all of the regions in Exhibit 2-2 are examined for 2000 to 2010,
rather than 1950 to 2010, to see more recent trends, the overall ratio of urbanized area growth to
population growth declines from 2.5 to 1.5. Again, this composite figure obscures noteworthy
 1 U.S. Census Bureau, "The Urban and Rural Classifications" 1994

                                              Status and Trends in Land Use, Buildings, and Travel Behavior




_ ^^^m m
•. "m

^^^ Land area (square miles)
* — —- — •
• 	 «---*^

0 T 1 1 1 1 1 1
1950 1960 1970 1980 1990 2000 2010

xhibit 2-3: Pittsburgh metropolitan region land area and population, 1950-2010. Land area
icludes the amount of land classified as part of the Pittsburgh urbanized area according to the U.S.
ensus Bureau.
ources: U.S. Census Bureau 1961 (Table 22), 1979 (Table 1), 1983 (Table 34), 1993 (Table 51), and
'hanges in Urbanized Areas from 2000 to 2010 2010

differences among cities. In this period, the populations of Cleveland, Pittsburgh, and Detroit declined as
their urbanized areas continued to expand, and most cities still showed urbanized area growth rates
that exceeded population growth rates.  However, several regions show the opposite trend: San Diego;
San Francisco-Oakland; Seattle; Portland, Oregon; Baltimore; Riverside-San Bernardino, California;
Washington, D.C.; Miami; New York-Newark; and Houston. For Baltimore; Washington,  D.C.; and New
York-Newark, the changing trend is particularly striking, with the number of acres of urbanized area land
per resident growing markedly between 1950 and 1980, then leveling off between 1980 and 2010
(Exhibit 2-4).
                                                                     I Baltimore
                                                                     I Washington
                                                                      New York-Newark
                            1960   1970
           Exhibit 2-4: Urbanized area per resident for the Baltimore, Washington, and New York-Newark
           urbanized areas, 1950-2010.
           Sources: See Exhibit 2-3

Status and Trends in Land Use, Buildings, and Travel Behavior
Data for all urbanized areas in the United States show that while the urbanized area population and
urbanized land area steadily increased between 1950 and 2010, the population per square mile of
urbanized areas decreased by more than 50 percent (see Exhibit 2-5). Changes between 1950 and 1980
largely drive this overall trend towards a more dispersed population; population density has remained
relatively stable since 1980.

Urbanized area population
Urbanized area land area (mi )
Population per square mile
Exhibit 2-5: United States urbanized area changes, 1950-2010. Results are not directly comparable across decades due to
changes in the definitions of urbanized areas.
Sources: U.S. Census Bureau 1961 (Table 22), 1979 (Table 1), 1983 (Table 34), 1993 (Table 51), 2004 (Table 6), and Percent
Urban and Rural in 2010 by State 2010

2.1.3   Developed Land

The U.S. Department of Agriculture publishes a Natural Resources Inventory that tracks developed land
using a different definition than the U.S. Census. According to the inventory, as of 1982, close to 71
million acres of non-federal land were developed nationally.14 By 2007, the number of acres rose to
more than 111 million, a 57 percent increase.15 Over this 25-year period, the population of the United
States increased about half as much (30 percent).16 Of the newly developed land, nearly half
(17,083,500 acres) had been forestland in 1982. About one quarter of it (11,117,500 acres) had been
cropland, and the remainder had been pastureland, rangeland, or other rural land.17 Exhibit 2-6 provides
an example of how land use changed over four decades in one metropolitan region.

States show considerable variation in the percentage of land that was developed over this time. For
example, while North  Dakota had just an 8 percent increase in developed land between 1982 and 2007,
the increase in Nevada was 145 percent. The other states with the highest percentage increase in
developed land over this 25-year period were Georgia (108 percent), North Carolina (107 percent),
Florida (99 percent), Arizona (97 percent), and South Carolina (97 percent).18

As development occurs, the transition zone between undeveloped and developed land, known as the
wildland-urban interface, has been expanding, increasing the number of homes surrounded by or
adjacent to natural areas. Development that occurs in patches isolated from other developed areas
creates new edges on all sides, which fragments habitat (see Section 3.1.3) and can significantly expand
the wildland-urban interface. One estimate found that the size of this transition zone grew 52 percent
  The National Resources Inventory category of developed land includes (a) large tracts of urban and built-up land,
(b) small tracts of built-up land of less than 10 acres, and (c) land outside of these built-up areas that is in a rural
transportation corridor (roads, railroads, and associated rights-of-way).
15 U.S. Department of Agriculture 2009
16 Calculated based on data from the U.S. Census Bureau (U.S. Census Bureau, Population and Housing Unit
Estimates n.d.).
17 U.S. Department of Agriculture 2009
18 U.S. Department of Agriculture 2009

                                                Status and Trends in Land Use, Buildings, and Travel Behavior
between 1970 and 2000.19 In
the western United States,
nearly 90 percent of this
interface occurs in areas with a
high risk of forest fires, making
the growth of housing in and
near this zone  of particular

Data on the extent of land
developed does not fully
capture development's
impacts because some areas
are more sensitive to  its
effects than others are. One
study found that housing in
and near wilderness, national
parks, and national forests has
increased since 1940. The
number of homes located
within 1 kilometer (0.62 miles)
of these protected areas
increased nearly fourfold, from
slightly less than half a million
in 1940 to slightly less than 2
million in 2000. New
residential construction within
national forests rose from
335,000 units in 1940 to nearly
1.3 million units 60 years later,
adding the equivalent of three
homes per square mile of national
      Top 20 most expanded CTUs from 1975 to 2006
      2030 MUSA boundary
      County boundary
      Agriculture to urban
      Forest to urban
      Other rural
  Exhibit 2-6: Land use change in Minneapolis-Saint Paul (the Twin Cities), 1975-
  2006. A study of land use change in the Twin Cities metropolitan urban service
  area (MUSA) between 1975 and 2006 showed that urban area increased by
  313,100 acres (about 83 percent), mostly in areas previously covered by forest,
  cropland, or wetlands. Most new growth occurred along major highways and
  roads at the periphery of the urban area or in new growth centers disconnected
  from the core. The seven counties that comprise the metropolitan area had a
  population growth rate of 45 percent during this same period, which
  corresponds to an annual growth rate of 1.5 percent, making this the eighth
  fastest growing area in the United States during that period. Shaded areas in a
  ring around the region show the top 20 most expanded cities, townships, and
  unorganized territories (CTUs) from 1976 to 2006.
  Image source: Yuan 2010. Reprinted by permission of the publisher (Taylor &
  Francis Ltd, www.tandf.co.uk/journals).
Coastal ecosystems are also particularly sensitive to the effects of development. Although coastal
watershed counties constitute 20 percent of total U.S. land area (excluding Alaska), in 2010 they
contained 52 percent of the U.S.  population and had an average density of 319 people per square mile
compared with 61 people per square mile in inland counties.22 A vulnerability index created by the U.S.
  Theobald and Romme 2007
 :Massada, et al. 2009
 1 Radeloff, et al. 2010
 '" National Oceanic and Atmospheric Administration 2013

Status and Trends in Land Use, Buildings, and Travel Behavior
Geological Survey23 identifies 6,734 miles (30 percent) of coastal shoreline in the United States as very
highly vulnerable to sea level rise and an additional 4,514 miles (20 percent) as highly vulnerable.24
Between 1970 and 2010, the population in the coastal flood plain increased 51 percent. As of 2010, 16.4
million people lived in the  coastal flood plain, an area at greater risk of inundation from storm surges
and long-term sea  level rise.25

2.2     Status of and Trends in Buildings

2.2.1   Housing Units

The housing industry is highly susceptible to market forces, and year-to-year fluctuations tend to track
overall economic health. After peaking in 2006 and surpassing the previous high set during the mid-
1980s, the number of new homes fell precipitously in the following years (Exhibit 2-7). About 700,000
new housing units  were built in 2010, compared to more than 2 million units four years earlier.26
           Exhibit 2-7: New residential construction, 1980-2010.
           Source: U.S. Department of Energy 2012
In spite of fluctuations in the number of new homes produced annually, the total number of homes in
the United States has grown steadily since 1940 (Exhibit 2-8). Between 1940 and 2010, the national
housing inventory grew  more than 250 percent, adding nearly 100 million homes, while population grew
by 134 percent or 176,580,969 people (Exhibit 2-1).
  U.S. Geological Survey, National Assessment of Coastal Vulnerability toSea-Level Rise n.d.
24 National Oceanic And Atmospheric Administration, Climate: Vulnerability of our Nation's Coasts to Sea Level Rise
  National Oceanic and Atmospheric Administration, Climate: U.S. Population in the Coastal Floodplain n.d.
26 U.S. Department of Energy 2012

                                               Status and Trends in Land Use, Buildings, and Travel Behavior


              ~ 100,000,000
              g> 80,000,000
              j?  60,000,000
              i°  40,000,000


 Mobile homes
I Apartments, 5 or more units
 Apartments, 2 to 4 units
I Attached homes
I Detached homes
                            1940 1950 1960 1970 1980 1990 2000 2011
          Exhibit 2-8: Total number of housing units in the United States, 1940-2011.
          Sources: U.S. Census Bureau, Historical Census of Housing Tables: Units in Structure n.d. and
          Selected Housing Characteristics n.d.
As the number of housing units increased, so did the average size of houses. Single-family homes built
between 2000 and 2005 are 29 percent larger than homes built in the 1980s and 38 percent larger than
homes built before 1950.27 The national average for single-family residences went from 1,660 square
feet in 1973 to more than 2,500 square feet in  2007 before dropping slightly in subsequent years
(Exhibit 2-9).

¥ 2,000
y. (
g. 1,500

_, J,*!***^^**
• ••••••>jar^~~
***** ****"

1973 1977 1981 1985 1989 1993 1997 2001 2005 2009
xhibit 2-9: Average size of single-family homes, 1973-2010.
ource: U.S. Census Bureau, Median and Average Square Feet of Floor Area in New Single-Family
louses Completed by Location n.d.

The trend toward larger homes has occurred while average household size has decreased. The average
U.S. household was 2.59 persons in 2010, compared with 3.01 in 1973 and 3.56 in 1947 (Exhibit 2-10).2S
Shifts in the composition of households drove this trend. In 1940, only 8 percent of households
  U.S. Department of Energy 2012
 ' U.S. Census Bureau, Current Population Survey 2011

Status and Trends in Land Use, Buildings, and Travel Behavior
contained only one person, and 51 percent of households had children under 18. By 2011, one-person
households had increased to 28 percent, and households with children had dropped to 29 percent.29
              "5 3.0
                  1947 1952 1957 1962 1967  1972  1977  1982 1987 1992 1997 2002 2007
           Exhibit 2-10: Average U.S. household size (in persons), 1947-2011.
           Source: U.S. Census Bureau, Current Population Survey 2011
2.2.2   Building Energy Use

In 2011, the U.S. building sector30 accounted for 41 percent of domestic energy use and 7 percent of
global energy use.31 Energy use has grown relatively steadily for both the residential and commercial
sectors  since the 1950s, although the residential sector has more year-to-year fluctuations (Exhibit
2-11), due to weather, consumer income, and overall economic activity. The building sector's energy use
quadrupled between 1950 and 2010 while the population roughly doubled (as shown in Exhibit 2-1) and
the housing stock more than tripled (as shown in Exhibit 2-8). In 2010, purchased electricity for space
heating and cooling, water heating, lighting, and appliances accounted for 71 and 78 percent of total
building energy consumption for the residential and commercial sectors,  respectively. Direct
consumption of natural gas and petroleum for heating and cooking accounts for the remaining energy
Buildings rely heavily on electricity for power. In 2010, just over 10 percent of the power generated by
the electricity sector came from renewable sources, predominantly hydroelectric.33 After purchased
  U.S. Census Bureau, 1940 Census of Population and Housing—Families 1943, Historical Census of Housing Tables:
Living Alone n.d., and American FactFinder n.d.
30 In this document, the building sector refers to residential and commercial buildings only. The residential building
sector includes single- and multi-family residences. The commercial building sector includes offices, stores,
restaurants, warehouses, other buildings used for commercial purposes, and government buildings.
31 U.S. Department of Energy 2012
32 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
33 U.S. Energy Information Administration 2011. The percentage of power generated by the electricity sector that
comes from renewable sources has varied between 7 and 14 percent since 1976. The share was 31 percent in 1949
and fell for the next 28 years.

                                                 Status and Trends in Land Use, Buildings, and Travel Behavior
                 ••£ 20,000
               %  £ 15,000
               = -c 10,000
                 '=  5,000
                                                                                 ' Residential
            Exhibit 2-11: Energy use in British thermal units (Btu) by building sector, 1949-2010. Energy use
            includes primary energy consumption, electricity retail sales, and electrical system energy losses.
            Source: U.S. Energy Information Administration 2011, Table 2.la
electricity, burning fossil fuels (i.e., natural gas, petroleum, and coal) is the next most common energy
source for buildings in both the residential (Exhibit 2-12) and commercial sectors (Exhibit 2-13). Between
1949 and 2010, fossil fuels accounted for between 76 and 95 percent of residential direct energy use,
with no clear trend over time. For the commercial building sector, essentially all  direct energy prior to
1988 came from fossil fuels, and use of renewable resources increased only slightly in later years. In
2010, just 3 percent of direct energy in the commercial building sector came from  renewable resources,
predominantly wood.34
               _ 20,000
                                                                    I Directrenewable energy use
                                                                    I Directfossil fuel use
                       1949   1959   1969   1979  1989  1999  2009
            Exhibit 2-12: Energy use from fossil fuels for residential buildings, 1949-2010. Renewable energy
            sources include geothermal, solar, photovoltaic, and wood. Electricity includes electricity retail
            sales and electrical system energy losses.
            Source: U.S. Energy Information Administration 2011, Table 2.1b
  U.S. Energy Information Administration 2011

Status and Trends in Land Use, Buildings, and Travel Behavior
                                                              I Directrenewable energy use
                                                              I Directfossil fuel use
                    1949  1959  1969  1979   1989   1999  2009
         Exhibit 2-13: Energy use from fossil fuels for commercial buildings, 1949-2010. Renewable
         energy sources include geothermal, solar, photovoltaic, wood, hydroelectric, and wind. Electricity
         includes electricity retail sales and electrical system energy losses.
         Source: U.S. Energy Information Administration 2011, Table 2.1c
The generation of energy used for buildings also requires water. Much of it is needed for cooling at
power plants.35 In 2005, fresh water withdrawals for electricity generation totaled 510 million gallons
from ground sources and 142 billion gallons from surface sources.36 Total water withdrawals including
saltwater were 201 billion gallons, which was the amount needed to generate 3.19 trillion kilowatt
hours of electricity.37 Thus, every kilowatt hour of electricity (enough energy to power a 100-watt light
bulb for 10 hours) requires 16 gallons of water, and 71 percent of that water comes from ground water,
lakes, and rivers.

2.2.3   Building Water Use

Buildings get water from the public supply and self-supplied sources such as surface water, wells, and
rainwater cisterns.38 Water consumption grew by 27 percent in the building sector between 1985 and
200539 (Exhibit 2-14), even as overall water use grew by less than 3 percent.40 In 2005, water
consumption in the residential and commercial building sectors accounted for 9.7 percent of all water
consumption in the United States, up from 7.8 percent in 1985.41

Earlier data are available tracking combined water withdrawals from the public supply (sourced from
both ground water  and surface water) for residential, industrial, and commercial use, as well as public
  Kenny, et al. 2009
36 Kenny, et al. 2009
37 Kenny, et al. 2009
38 Kenny, et al. 2009
39 The U.S. Geological Survey does not expect to release source data for 2010 until 2014 (U.S. Geological Survey,
Water Use in the United States n.d.).
40 U.S. Department of Energy 2012
41 U.S. Department of Energy 2012

                                              Status and Trends in Land Use, Buildings, and Travel Behavior
                                                                            I Commercial
           Exhibit 2-14: Water use in the building sector, 1985-2005. For the years 2000 and 2005, the split
           between commercial and residential use is based on extrapolation from 1995 data.
           Source: U.S. Department of Energy 2012
services and system losses. Per capita withdrawals between 1950 and 1980 increased more than
60 percent but then largely leveled off between 1985 and 2005 (Exhibit 2-15). In 2005, on average,
58 percent of the total withdrawals from the public supply were for indoor and outdoor residential use,
although results varied by state, from 39 percent in Pennsylvania to 79 percent in  Maryland.42

™ 1"
5 °~ OQ
ra £
u tio

^ — • — • — •


0 n i i i i i i i i i i i
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
xhibit 2-15: U.S. per capita water withdrawals from the public water supply, 1950-2005.
ource: Kenny, et al. 2009

Water use in commercial buildings varies by season and depends on a host of factors, including the
building's size, function, and location. In residential buildings, water use averages about 100 gallons per
person per day.43 However, per capita residential water use varies considerably by state, driven in large
measure by greater outdoor water use in arid regions. In 2005, the lowest per capita use was in Maine
  Kenny, et al. 2009
 ' U.S. Department of Energy 2012

Status and Trends in Land Use, Buildings, and Travel Behavior
(54 gallons per day), Pennsylvania (57 gallons per day), Wisconsin (57 gallons per day), Delaware
(61 gallons per day), and Vermont (64 gallons per day). The highest per capita use was nearly triple
these rates in Nevada (190 gallons per day), Idaho (187 gallons per day), Utah (186 gallons per day),
Hawaii (165 gallons per day), and Wyoming (152 gallons per day).44

Buildings and building occupants use water for various indoor and outdoor activities including drinking;
bathing; cleaning; cooking; watering lawns and landscaping; supplying fountains and other water
features; and running cooling towers for heating, ventilating, and air conditioning. An analysis of 1,188
single-family homes showed that outdoor uses (e.g., lawn and landscaping irrigation and swimming
pools) accounted for about one-third of all water used, followed by toilets, washing machines, faucets,
and showers (Exhibit 2-16),45 although this likely varies considerably depending on climate. Exhibit 2-17
shows how several types of commercial and institutional facilities use water.
                                                                      dishes, 1%
Showers,  9%
N- Baths, 1%
 ^^ Other indoor
     uses, 2%
          Exhibit 2-16: Single-family home water consumption by end uses, 1999.
          Source: U.S. Department of Energy 2012
Water use affects more than just the amount of water withdrawn from underground aquifers, surface
water bodies, and other sources. Water treatment and distribution are highly energy-intensive, as are
many water uses that involve heating, chilling, softening, or pressurizing it for various needs.46 Uneven
data availability across states and methodological difficulties make analysis of the energy consumption
associated with water use difficult.47 One analysis estimated it took 39 billion kilowatt hours of
electricity to supply water to the building sector in 2005, a value that represented about 1 percent of
total electricity produced by all power plants in the United States that year.48 Another study estimated
that the residential sector consumes 2,747 trillion British thermal units (Btu) of energy annually for
water services, primarily for heating water, while the commercial sector consumes 1,657 trillion Btu of
  Kenny, et al. 2009
 ' U.S. Department of Energy 2012
 ' Sanders and Webber 2012
 ' Sanders and Webber 2012
 ! U.S. Department of Energy 2012

                                             Status and Trends in Land Use, Buildings, and Travel Behavior
                                                                    Medical equipment
                                                                   I Cooling and heating
                   Hospitals    Offices    Schools   Restaurants  Hospitality
          Exhibit 2-17: Water use in commercial and institutional facilities.
          Source: EPA, WaterSense at Work 2012
energy annually for water services, primarily at public water and wastewater treatment facilities and for
heating water. Based on these figures, combined water use in the residential and commercial sectors
accounted for roughly 4.5 percent of national energy consumption in 2010.49

2.2.4   Building Construction Waste Production

Buildings use a lot of construction materials that result in an equivalent amount of demolition debris
during renovations and at the end of their lifecycle. Much of this material is shipped to landfills
specifically designated for construction and demolition waste, while in some areas it is discarded with
municipal solid waste in landfills, used as fill in quarries or pits, or incinerated.50 Cement concrete alone
accounts for about half of the 65 million tons of demolition debris produced each year.51 EPA estimated
that in 2003 the building sector produced an estimated 170 million tons of construction, renovation, and
demolition waste.52 Another estimate of construction and demolition  debris from the  building sector-
based on the total amount of construction material used over time, its typical service life, and the
amount of material discarded during construction—was 209 million tons in 2002.53 Construction and
demolition waste includes wood, drywall, asphalt, concrete, cardboard, glass, masonry, roofing  material,
plastic, and metal. Commercial renovation was the leading source of construction and demolition waste
in 2003, followed by demolition waste from commercial and residential buildings (Exhibit 2-18).
Although information is not available on trends in the amount of construction and  demolition waste
produced over time, as the size of single-family homes has increased (Exhibit 2-9), the amount of
materials used for home construction and the amount of waste that will be generated at the end of the
homes' lifecycle have likely also increased.
  Sanders and Webber 2012
 ' EPA, Estimating 2003 Building-Related Construction and Demolition Materials Amounts 2009
  Horvath 2004
 " EPA, Estimating 2003 Building-Related Construction and Demolition Materials Amounts 2009
 ! Cochran and Townsend 2010

Status and Trends in Land Use, Buildings, and Travel Behavior
           Exhibit 2-18: Amount of construction and demolition waste generated from building activities,
           2003. Although renovation of a building produces less waste than demolition and construction of a
           new building, considerably more renovation activity occurs, making it a larger contributor to
           overall amounts of construction and demolition waste.
           Source: EPA, Estimating 2003 Building-Related Construction and Demolition Materials Amounts
           2009, Table 2-7
While in aggregate, new construction generally produces less construction and demolition waste than
demolition and renovation, the construction of a new single-family detached residence can generate up
to 7 tons of waste and 15 to 70 pounds of potentially hazardous substances such as paint, caulk, roofing
cement, aerosols, solvents, adhesives, oils, and greases. One study estimated that in the U.S. residential
building sector, construction contributes more hazardous waste and toxic air emissions than building
use or demolition based on estimates of the amount of construction and demolition activity occurring in
a single year (1997).54

2.3    Status of and Trends in Infrastructure

The increase in developed  land and buildings in the United States has occurred along with an increase in
transportation and other infrastructure needed to serve  an increasingly dispersed population.

2.3.1   Roads

Roads alone represent a considerable portion of the built environment. In 2010, the United States had
more than 4 million miles of roads owned and maintained  by a public authority and open to public
travel (Exhibit 2-19). The amount of annual road construction was greatest during the 1910s and then
  Ochoa, Hendrickson, and Matthews 2002. Construction included acquisition of raw materials, manufacturing,
transportation to the construction site, and actual construction. The study compared this phase with usage, which
included remodeling, improvements, and occupant energy usage, and demolition, which included the demolition
process and debris transportation.

                                             Status and Trends in Land Use, Buildings, and Travel Behavior
              £ 2,500,000
              ^ 2,000,000
                       1900  1910  1920  1930  1940 1950 1960 1970 1980  1990  2000  2010
          Exhibit 2-19: United States public road mileage, 1900-2010.
          Source: Federal Highway Administration 2010
leveled off until another period of expansion in the 1950s and 1960s. Although the rate of new road
construction has slowed since then, 114,576 lane miles of public roads were built between 2000 and
2005, and another 277,385 lane miles were added in the following five years.55

The total amount of land covered by roads does not capture their full impact because their
environmental effects extend beyond the pavement edge (see Section 3.1.4). As more lane miles are
built, the amount of land they affect increases. In 2001, 20 percent of all land in the contiguous United
States was within 417 feet of a road, and 50 percent was within a quarter-mile. Only about 18 percent of
all land was more than 0.62 mile from a road, and about 3 percent was more than 3 miles.56

2.3.2  Parking

Parking structures and parking lots are also significant components of our transportation infrastructure
in terms of the amount of land they cover. In 2010, more than 242 million cars, buses, and trucks were
registered in the United States,57 and each requires a place to park at home and other destinations.
Estimates of the total parking inventory in the  United States vary widely due to differences in
methodology. A 2010 study developed five scenarios based on existing literature to estimate the total
number of parking spaces and the land area they consumed. The middle scenario was based on the
number of known for-pay parking spaces, estimates of the amount of parking provided per square foot
of commercial space, estimates of on-street parking based on road design specifications, and
assumptions that each car had a home space and work space. This scenario estimated 820 million
parking spaces covering 8,500 square miles.58 If combined with the amount of space devoted to roads,
an estimated 23,900 square miles of the United States is paved for driving and parking, an area nearly
 ' Federal Highway Administration 2010
 ' Riitters and Wickham 2003
  Federal Highway Administration 2010
 ! Chester, Horvath, and Madanat 2010

Status and Trends in Land Use, Buildings, and Travel Behavior
the size of West Virginia.59 More precise
estimates have been made in smaller
regions using satellite images. For example,
a study of Tippecanoe County, Indiana,
found that parking alone covers 2.2 square
miles, 0.4 percent of the total land and
6.6 percent of the developed area in the
                                             Exhibit 2-20: Parking Lot. Parking lots, many of which regularly
                                             sit empty, cover significant amounts of land.
                                             Photo source: EPA
2.3.3  Water, Wastewater, Utilities,
       and Other Infrastructure

Reliable national data on the extent of
centralized water and wastewater, utilities,
and other infrastructure and how they have
changed over time are unavailable. One estimate, based on a survey of utilities and extrapolated based
on the population they served, estimated that the United States has 995,644 miles of pipes in its water
distribution network.61 Another analysis estimated the United States has 800,000 miles of drinking water
pipes and  between 600,000 and  800,000 miles of wastewater pipes.62 As noted in Section 2.1.2, as the
population has grown, population density has decreased in nearly all metropolitan regions. With this
change, the amount of centralized infrastructure needed per person has likely also increased as
distances between houses have grown.

In addition to materials needed for construction, repair, and replacement of infrastructure, centralized
water and wastewater infrastructure itself has major environmental effects. The energy needed to move
water and wastewater increases as centralized systems cover more land. A larger system also creates
more opportunity for treated drinking water and untreated wastewater to be lost through leaks because
of both the length of the pipes and the additional pressure needed to  push waterthrough longer pipes.

Many households rely on decentralized water and wastewater infrastructure, and this pattern continues
for newly built homes. In 2011, 11 percent of all households and 11 percent of households in a home
built in the last four years used a well as their primary source of water. For wastewater infrastructure,
19 percent of all households and 21 percent of households in a home  built in the last four years relied
on a septic tank, cesspool, or chemical toilet.63 These types of decentralized wastewater systems can
release nitrogen and phosphorus to both ground and surface water. Although nitrogen and phosphorus
are important nutrients, in excess they can contribute to an overgrowth of aquatic plant life that
depletes oxygen other aquatic species need to survive. Conventional septic systems remove less than
  Chester, Horvath, and Madanat 2010
 'Davis, etal. 2010
  EPA, Distribution System Inventory, Integrity and Water Quality 2007
 ' U.S. Government Accountability Office 2004
 ! U.S. Census Bureau, American FactFinder n.d., Table C-04-AO

                                            Status and Trends in Land Use, Buildings, and Travel Behavior
half of the nitrogen from wastewater, although advanced treatment systems can remove much more.64
Although septic systems release treated wastewater to soils, which can better retain phosphorus, septic
systems can still lead to phosphorus discharges to ground and surface water depending on soil
characteristics, septic system placement, and use of phosphorous-containing household products.65 In
addition, improperly maintained systems can discharge untreated or inadequately treated wastewater.66

2.4    Status of and Trends in Impervious Cover

Land development—the buildings and roads we construct for housing, commercial activity, industry, and
transportation—creates impervious surfaces that water cannot penetrate. Under natural conditions,
only about  10 percent of the annual rainfall becomes surface runoff; the rest either soaks into the soil or
is taken up  by vegetation and transpired.67 As development occurs, impervious surfaces—including
roofs, roads, driveways, sidewalks, and patios—replace vegetation, and more and more rainwater
travels as runoff from the area where it fell. The environmental effects of this change are varied and can
be significant even if only a small proportion of a watershed is developed (see Section 3.2). The
proportion  of a  watershed that is covered with impervious  surface can serve as a good indicator of the
degree to which development affects water ecosystems and water resources.68

A national estimate  of impervious cover in the contiguous United States (total area 3,035,033 square
miles) found that the total impervious surface area in 2006 was 40,006 square miles, an area slightly
smaller than the state  of Kentucky, and a 4 percent increase since 2001.69 The states with the largest
percentage increases were Arizona (8.9 percent), Georgia (8.4 percent), and South Carolina
(7.9 percent). The states with the largest absolute increases in impervious surface area during this five-
year period were Texas (212 square miles, a 6.0 percent increase), California (122 square miles, a
3.7 percent increase), and Florida (107 square miles, a 5.7 percent increase). In most places, most new
impervious cover formed a ring around central cities.

An earlier analysis estimated the amount of impervious surface in the  contiguous United States to be
32,317 square miles in 2000.70The study used a housing density model to estimate the distribution of
this impervious cover among watersheds. It found that impervious cover was at levels likely to affect
water quality in almost 25 percent of watersheds by area (Exhibit 2-21).

Although many large watersheds still contain relatively small percentages of impervious cover, overall
impervious cover is not necessarily a good indicator of whether there  are local effects. Impervious cover
64 Carey, et al. 2013
65 Carey, et al. 2013
66 Carey, et al. 2013
67 Federal Interagency Stream Restoration Working Group 1998
68Sutton, etal. 2009
69 Xian, et al. 2011. This estimate is based on the U.S. Geological Survey's National Land Cover Database.
70 Theobald, Goetz, et al. 2009. This estimate is comparable to others and supported by validation data sets,
although the methodology used is known to under-represent impervious cover in areas with commercial and
industrial land uses. The estimate for 2000 is 16 percent less than Xian, et al. estimated for 2001.

Status and Trends in Land Use, Buildings, and Travel Behavior
Watershed classification
Lightly stressed
Percent impervious cover
Number of watersheds
Percent by area
              Exhibit 2-21: Number and percentage by area of watersheds affected by impervious cover
              levels, 2000. For this analysis, watershed boundaries were determined by 10-digit hydrologic
              unit codes, a classification system that divides the country into nested hydrologic units.
              Source: Theobald, Goetz, et al. 2009

is often concentrated in particular areas, and smaller watersheds contained within larger watersheds
can have much higher relative levels. For example, most cities have levels of impervious cover that are
known to stress or even seriously degrade water quality.71 Estimates of impervious cover for 18 cities
throughout the  United States ranged from 61 percent in New York City to 18 percent in Nashville.72 The
percentage of impervious cover across all of these cities grew in the mid to late 2000s on average by
0.31 percent per year, or 23.7 square feet per person per year, at the same time that these cities lost
tree canopy cover. For example, Houston's impervious cover grew on average 0.26 percent while it lost
0.60 percent of  its tree cover every year
between 2004 and 2009. Tacoma,
Washington's impervious cover grew on
average 0.89 percent while it lost
0.36 percent of  its tree cover every year
between 2001 and 2005. Syracuse, New
York, is the only one of the 18 cities that
both increased tree cover, which grew on
average by 0.17 percent per year from
2003 to 2009, and reduced impervious
cover, which declined  by 0.09 percent per
year. The increase in tree cover in
Syracuse was due predominantly to
growth of invasive European buckthorn,
suggesting that natural regeneration and
limited development activity is
responsible for the change. Exhibit 2-22
shows an example of how the amount of
impervious cover changed in two
Washington counties over 34 years.
                          Percent Impervious Surface Change: 1972-2006

                               0%       100%
Exhibit 2-22: Impervious cover change in Snohomish and King
counties, Washington. Satellite imagery for a portion of
Snohomish and King counties, Washington, was analyzed to
estimate the increase in impervious cover between 1972 and 2006.
Over this 34-year period, the area of impervious surface increased
by 255 percent (8,117 to 28,793 acres), while population increased
by 79 percent. About three-quarters of the new impervious area
was added in relatively low-density locations that were outside of
the counties' designated urban growth areas (outlined in blue).
Image source: Powell, et al. 2008. Reprinted by permission of the
publisher (Elsevier).
  Theobald, Goetz, et al. 2009
72 Nowak and Greenfield 2012. Cities were selected based on available data and existing projects and for
geographic representation across the country. City boundaries were defined by census-incorporated place or
census-designated place boundaries. The years analyzed for each city vary slightly based on the dates of available
aerial images.

                                            Status and Trends in Land Use, Buildings, and Travel Behavior
2.5   Status of and Trends in Travel Behavior

Numerous factors have contributed to an increase in vehicle travel since the 1950s. For example, the
size of the U.S. labor force affects how many people commute to work in cars. The U.S. labor force was
roughly 59 percent of the working-age population in 1948.73 It remained relatively constant until the late
1960s. From then  until 2000, it grew to a peak of 67 percent, then declined slightly and rose again to
66 percent in 2006. A substantial portion of the increase in labor force participation until 2000 was due
to women, particularly married women, joining the workforce. An increasing Hispanic population also
explains some of the increase, as Hispanic men tend to have the highest workforce participation rates.74

A combination of rising incomes and falling fuel prices in the latter half of the twentieth century also
affected vehicle travel. As household incomes increased and fuel prices fell, families could afford one or
more cars. In 1969, 79 percent of U.S. households owned one or more vehicles. By 1995, that figure had
grown to 92 percent. However, between 2001 and 2009 the number of households with no vehicle grew
by nearly 1 million, rising from 8.1 to 8.7 percent of all households (Exhibit 2-23).
                                                                  No vehicle
                                                                  One vehicle
                                                                  Two vehicles
                                                                  Three or more vehicles
                      1969   1977   1983   1990  1995  2001   2009
2-23: Vehicles per household, 1969-2009. The 1969 data do not include pick-ups or light

Federal Highway Administration 2011
In addition to shifting demographics and household finances, much of the increase in vehicle travel is
likely a result of outward growth of cities and towns and the roads built to serve the new development.
Since the 1950s, development has become more dispersed (Exhibit 2-5). With more households living on
large lots far from the economic centers of their communities, workplaces and housing have become
more segregated from one another, and distances between everyday destinations have grown. More
people used cars for most or all of their trips at the same time that the design of communities changed
  DiCecio, et al. 2008
  DiCecio, et al. 2008. Much of the decline since 2000 can be attributed to a large segment of the population
retiring and a sharp decline in teenage workforce participation.

Status and Trends in Land Use, Buildings, and Travel Behavior
to accommodate more cars. These changes have in turn made it impractical or impossible for many
people to get around by any means other than a car, further reinforcing community design that
precludes other choices.

2.5.1  Vehicle Travel

While the population roughly doubled between 1950 and 2011, from about 152 million to 312 million
people, vehicle travel during this same period increased nearly sixfold, from around 458 billion vehicle
miles traveled (VMT)75 to nearly 3 trillion VMT (Exhibit 2-24).
                                                                    • VMT growth
                                                                    • Population growth
                 1950    1960    1970    1980    1990    2000   2010
          Exhibit 2-24: Growth in VMT and population, 1950-2011. Data are normalized to a 1950 value of
          Sources: Federal Highway Administration 2010 and 2012; U.S. Census Bureau 2000, 2009, and
          State & County QuickFacts n.d.
The decline in VMT since 2007 (see Exhibit 2-24), the rise in households with no car between 2001 and
2009 (Exhibit 2-23), labor force changes noted above, and other evidence suggest that the decades-long
growth of VMT might be slowing. Historically, household income has mirrored VMT, growing at about
the same rate—a much higher rate than population growth—and showing similar patterns during
economic expansions and contractions. However, since 1997, the trends in household income and VMT
have diverged. From 1970 to 1997, VMT grew at 3.0 percent  per year, while household income grew at
3.2 percent. From 1997 to 2005, VMT grew at 2.0 percent per year, compared to 3.2 percent for
household income.76 It is unclear why growth in VMT appears to have leveled off or whether the trend
will continue, particularly if the rate of economic growth increases. However, research suggests that
travel demand might have reached a saturation point as drivers are unwilling to devote more time to
 ' Vehicles include passenger cars; other two-axle, four-tire vehicles; motorcycles; and buses.
 ' Memmott2007

                                              Status and Trends in Land Use, Buildings, and Travel Behavior
travel, infrastructure improvements no longer allow substantial speed increases, and the marginal
benefits of additional trips or travel to additional destinations are not worth the marginal cost.77

VMT depends on trip lengths, trip frequencies, and people's choices about how to get around.78 The
increase in VMT thus is related to how close people live to where they work and take care of daily
activities,  and whether they have viable alternatives to driving. Data from the National Household Travel
Survey suggest the number of car trips taken per person could explain more of the rise in VMT than the
length of those trips, at least until the mid-1990s. The annual number of vehicle trips taken per
household increased from 1,396 in 1969 to a maximum of 2,321 in 1995, falling to 2,068 in 2009,  while
the average vehicle trip length was relatively constant (Exhibit 2-25).79 While average household size
declined in the United States from 3.2 people in 1969 to 2.5 people in 2009, the average number  of
vehicles per household increased from  1.2 to 1.9 in the same period. The number of workers and the
number of licensed drivers in the United States also more than doubled, explaining in part the increase
in the number of trips taken and the increase in VMT.80
                                                              •Vehicle trips per household
                                                              •Average vehicle trip length
         Exhibit 2-25: Growth in annual vehicle trips per household and average vehicle trip length,
         1969-2009. Data are normalized to a 1969 value of 1.0.
         Source: Federal Highway Administration 2011
2.5.2   Induced Travel

Many researchers have studied the possible effects of additional road capacity on VMT. Induced travel is
a term for traffic growth produced by the addition  of road capacity. The theory behind induced travel is
  Millard-Ball and Schipper 2011
78 Ewing and Cervero 2010
  The percentages of trips taken by personal vehicle and by public transit were also relatively constant, although
data were available only from 1990 to 2009. The percentage of trips made by foot varied between 1990 and 2009
but did not show a consistent trend over time. Interpretation of results for alternative forms of transportation is
also complicated by a change in the survey to explicitly ask respondents about walk trips.
80 Federal Highway Administration 2011

Status and Trends in Land Use, Buildings, and Travel Behavior
that of supply and demand. Adding road capacity (supply) reduces the cost of vehicle travel by reducing
the costs associated with travel time. When cost goes down, demand goes up. As travel time and
monetary costs fall, people travel more.

Different types of induced travel would be expected to occur in the short and long terms. In the short
term, additional road capacity can lead to people making more trips, increasing trip length, changing the
time of travel, or switching from transit or carpools to driving alone because of improved traffic
conditions. In the long term, reduced travel costs can encourage more dispersed land use patterns that,
in turn, could increase trip lengths and vehicle dependency, leading to a permanent increase in travel

Researchers have long attempted to determine whether additional road capacity actually causes
increases in VMT and how great the effect might be.81 A 2002 review of studies found strong evidence
that additional transportation capacity induces travel, both from short-term increases in demand and
from long-term changes in land use.82 Evidence suggests a 10 percent increase in lane miles increases
VMT by 3 to 6 percent, although a more recent study found more modest effects.83 Most recently, a
2011 analysis of city-traffic and road data for 228 metropolitan areas in the United States between 1983
and 2003 found that a 10 percent increase in lane miles on interstate highways was associated with a
10 percent increase in VMT.84 For other major roads, the  increase in VMT was slightly less. Results of this
study suggest that the primary cause of the increase was additional truck traffic and an increase in
individual VMT rather than population growth in areas with new highways or diversion of traffic from
other routes. A study contrary to most results reported no evidence of induced travel.85 However, this
research evaluated trips taken rather than total miles traveled, and this inconsistency could be
explained if individual VMT growth is due less to people taking additional trips than to people choosing
to travel longer distances to accomplish the same goal  or people switching from another form of travel
to a car. In fact, evidence suggests that as travel speeds improve, people are willing to travel farther and
often do. Average travel time per person per year has remained relatively constant in spite of large
increases in road capacity.86 Although the magnitude of the effect remains uncertain, most evidence
suggests that additional road capacity does lead to increased VMT.

Researchers have also investigated whether additional road capacity can cause increases in other types
of development.  A  review of the literature on highway-induced development shows that new highways
have little effect on the  total amount of development that occurs in a metropolitan area. However, they
can have large effects on the location  of the development that occurs.87 Highways tend to drive
81 Handy 2005
82Nolandand Lem 2002
83 Cervero 2003
84 Duranton and Turner 2011
85 Mokhtarian, etal. 2002
87 Ewing 2008

                                              Status and Trends in Land Use, Buildings, and Travel Behavior
development to areas where they provide improved accessibility, favoring locations outside of central
cities and leading to conversion of undeveloped land.

2.5.3   Transit, Walking, and Bicycling

Since the middle of the last century, relatively few people have gotten to work by using public
transportation, carpooling, bicycling, or walking. Over most of the last 30 years, these forms of
commuting have declined steadily in most areas, with the exception of some cities and towns. Census
data on mode choice from 1980 to 2010 show a downward trend in carpooling and walking to work
(Exhibit 2-26). Public transportation use also declined  each decade from 1980 to 2000 but showed a
slight increase in 2010 over 2000  levels. Biking has remained the commuting choice for a relatively
constant but very small proportion of all workers. Census data before 1980 did not distinguish between
driving alone and carpooling or include information on motorcycle or bicycle use. However, in 1960,
12 percent of people usually took public transportation to work, 2.5 times the percentage in 2010, and
10 percent of people usually walked to work, 3.5 times the percentage in 2010.88
3:9%     m
•5.3%	4.7%	49o/0-
        2.2%	10.4%	      Worked at home
i      • Not reported
                         • Other means

                         • Walked only

                         • Bicycle

                         • Motorcycle

                          Public transportation


                          Drove alone
                                            1990     2000     2010
           Exhibit 2-26: Means of transportation to work, 1960 to 2010. Data for 1960 and 1970 group
           carpooling and driving alone together and do not include bicycle or motorcycle use. Data for 1960
           only include a "not reported" category.
           Sources: Davis, Diegel, and Boundy 2012, Table 8.16 and U.S. Census Bureau, Means of
           Transportation to Work for the U.S. n.d.
Although nationally only a small percentage of people bike or walk to work, there is considerable
variation across the country. In 2009, the top metropolitan areas for the percentage of workers who
commute by bicycle included Corvallis, Oregon (9.3 percent); Eugene-Springfield, Oregon (6.0 percent);
Fort Collins-Loveland, Colorado (5.6 percent); Boulder, Colorado (5.4 percent); and Missoula, Montana
(5.0 percent). Each of these cities has more than eight times as many people commuting by bike as the
 ' U.S. Census Bureau, Means of Transportation to Work for the U.S. n.d.

Status and Trends in Land Use, Buildings, and Travel Behavior
national average of 0.6 percent.89 A similar pattern is apparent with walking to work. In 2009, the top
metropolitan areas for the percentage of workers who walk to work included Ithaca, New York
(15.1 percent); Corvallis, Oregon (11.2 percent); Ames, Iowa (10.4 percent); Champaign-Urbana,  Illinois
(9.0 percent); and Manhattan, Kansas (8.5 percent), all well exceeding the national average of
2.9 percent.90

Commuting by public transportation and carpooling shows some racial and ethnic differences. In 2009,
white workers were most likely to drive alone (83.5 percent) and least likely to use public transportation
(3.2 percent). Black workers used public transportation at more than three times the rate of white
workers and showed a commensurate decrease in the percentage that drove alone. Asians, Hispanics,
and other races were also more likely than white workers to use public transportation and carpool. The
rate of walking to work was relatively constant
across racial and ethnic groups, ranging from
2.8 to 4.4 percent.91 These differences are
likely due at least in part to differences in the
availability of public transportation and
carpooling to people depending on where they
live. They are also likely due in part to
differences in car ownership rates among
racial and ethnic groups. In  2011, the
percentages of households without a car were
6.6 percent for whites (not Hispanic or Latino),
20.2 percent for blacks or African-Americans
(not  Hispanic or Latino), 11.7 percent for
Asians, and 12.8 percent for Hispanics or
Latinos (of any race).92

While adults are less likely to walk to work,
children are also less likely to walk to school
than in past decades. In 1969, nearly half of
students in kindergarten through eighth grade
walked to school. By 2009, that figure had
fallen to 13 percent.93 During that time, the
percentage of students who rode a school bus
stayed relatively constant, while the
percentage of students who were driven to
school increased. Walking or biking to school
Exhibit 2-27: Bike lane near Filter Square, Philadelphia.
Students and workers take advantage of a dedicated bike lane
to get exercise on the commute to work and school.
Photo source: Kyle Gradinger via flickr.com
 ' U.S. Census Bureau, Commuting in the United States: 2009 2011
 ' U.S. Census Bureau, Commuting in the United States: 2009 2011
  U.S. Census Bureau, Commuting in the United States: 2009 2011
  U.S. Census Bureau, American FactFinder n.d.
  McDonald, etal. 2011

                                             Status and Trends in Land Use, Buildings, and Travel Behavior
correlates with overall levels of physical activity for school children,94 and there is some evidence that
walking or biking to school can also improve measures of physical fitness.95 Section 3.7 discusses more
fully how the built environment affects activity levels, obesity, and chronic disease.

Commuting captures a lot of the public's attention because congestion tends to peak during rush hour,
and people generally have relatively little ability to avoid it because of limited control over when and
where they travel. However, the National Household Travel Survey96 shows the importance of non-work
trips to overall VMT; they accounted for nearly three quarters of all miles traveled in 2009. These data
also show that people tend to use personal vehicles more often for commuting than for other types of
travel, including social and recreational trips and travel to church. For example, the data show that for
2009, a personal vehicle was used for 91 percent of trips to "earn a living" but only 82 percent of non-
work trips,97 while walking was used for 3 percent of trips to earn a living but 12 percent of non-work
trips. However, in terms of miles of travel, differences in mode of transportation between work and
non-work trips were not as large.98

2.6    Future Trends

2.6.1  Projected Population Growth

The U.S. population is projected to grow 42 percent  between 2010 and 2050, from 310 million to
439 million."These new people will need additional housing and infrastructure. Researchers estimate
that  between 2005 and 2050, the United States will need 42 percent more, or 52 million, new housing
units. In addition, 37 million units will likely be built to replace existing homes.100 Together, the number
of new and replacement units projected to be built in this time is equivalent to about two-thirds of the
132 million housing units that existed in 2011.101 Researchers also estimate that between 2005 and
2050, the amount of nonresidential space will grow by about 60 percent to 160 billion square feet, and
about 130 billion square feet of nonresidential space will be rebuilt, some structures more than once.102
These projected trends present an opportunity to improve the environmental performance of our built
environment. Where and how we build new housing and infrastructure needed to accommodate
projected population growth will  have important environmental impacts (as discussed in Chapter 4).
94 Faulkner, etal. 2009
95Lubans, etal. 2011
  Federal Highway Administration, National Household Travel Survey n.d.
97 Non-work trips include the categories family/personal business, school/church, social and recreational, and
98 Results were calculated based on data collected using the National Household Travel Survey Data Extraction Tool
(Federal Highway Administration, Data Extraction and Visualization Prototypes n.d.).
99 Vincent and Velkoff 2010
100 Ewing, Bartholomew, et al. 2008
   U.S. Census Bureau, State & County QuickFacts n.d.
102 Ewing, Bartholomew, et al. 2008

Status and Trends in Land Use, Buildings, and Travel Behavior
2.6.2  Projected Land Conversion

Based on population projections and current development patterns, one study projects the amount of
urban land103 in the contiguous United States to more than double between 2000 and 2050, increasing
from 3 percent to 8 percent.104 Overall, researchers project that about 45,700 square miles of forestland
in nonurban areas in the United States in 2000, an area approximately the size of Pennsylvania, will be
located within an urban area in 2050, and much of this forestland would be lost to buildings, roads, and
other infrastructure.105 However, the distribution of this projected development is not equal across the
48 contiguous states. Researchers project that more than 50 percent of four states will be urban land by
2050: Rhode Island (71 percent), New Jersey (64 percent), Massachusetts (61 percent), and Connecticut
(61 percent). Projections for these states also indicate that they will have the greatest percentage of
land that is currently forest become part of an urban area by 2050. However, these states together
account for only 3,472 square  miles of non-urban forestland  projected to be subsumed by urban areas
between 2000 and 2050. Other states account for a larger absolute area projected to be subsumed by
urban areas in this period, including North Carolina (3,375 square miles), Georgia (2,994 square miles),
New York (2,630 square miles), Pennsylvania (2,451 square miles), Texas (2,404 square miles), Alabama
(2,074 square miles), and South Carolina (2,029 square miles).

The U.S. Forest Service also periodically assesses trends in the nation's renewable resources to project
future forest conditions and evaluate the implications of those projections for the ecosystem services
forests provide (see Section  3.1.1). The 2010 assessment is based on three scenarios that vary in
population and personal income projections (see Section 4.3 for a discussion of scenario planning).106 It
forecasts that between 1997 and 2060, 60 to 86 million acres of rural land (as much as the size of New
Mexico) will be developed, and between 24 and 38 million acres of forests (as much as the size of
Florida), 19 and 28 million acres of cropland (as much as the size of Tennessee), and 8 and 11 million
acres of rangeland (as much as the size of Vermont and New Hampshire together) will be lost.

2.6.3  Projected Changes in Development Trends

The extent to which current development trends  continue—and the amount of forestland, wetlands,
and other natural areas that will be lost—will depend on many factors. Market preferences, led by
changing demographics, will certainly influence the nature of future development. The aging of the U.S.
population and immigration are the two main drivers of projected demographic trends. Researchers
project the age structure of the U.S. population to shift from 13 percent aged 65 and older in 2010 to
19 percent in 2030. The aging of the baby boom generation107 will  shrink the percentage of the
population that is of working age (20-64) from 60 percent in 2010 to 55  percent in 2030, a decrease that
   Urban land was determined according to the U.S. Census Bureau's 2000 definition.
104 Nowak and Walton 2005
105 Nowak and Walton 2005
106 Wear 2011
107 People born between 1946 and 1964 are part of the baby boom generation.

                                            Status and Trends in Land Use, Buildings, and Travel Behavior
would be more significant if not for growth in the number of working-age immigrants.108 At the same
time, demographic projections indicate that the percentage of households with children will decline,
from 33 percent in 2000 to 27 percent in 2030. During this time, 83 percent of the net growth in
households is projected to consist of households without children.109 Thus, their needs and the needs of
the large baby boom population are expected to dominate the housing market until around 2030, after
which a decline in the number of baby boomers is expected  to have an equally significant impact on
housing needs.110 A literature review by the National Research Council shows that expected
demographic changes are likely to influence housing preferences and travel patterns in ways that could
shift real estate development towards more compact growth in which residents travel less to meet their
daily needs.111

2.7    Summary

The size of virtually every metropolitan area in the United States has expanded dramatically in recent
decades. In many places, the rate of land development has far outpaced the rate of population growth,
although more recent trends in some areas suggest the pattern could be changing. As the amount of
developed land has increased and more and larger homes have been built, buildings, roads, and
associated impervious surfaces have grown to serve an increasingly dispersed population. As our
communities changed to accommodate cars, the percentages of people taking public transit, walking,
and biking declined. Projected population growth and demographic trends suggest that the need for
additional development will continue to grow, providing an opportunity to improve the environmental
performance of our communities. The next chapter discusses some of the environmental impacts of our
current land use and travel behavior.
108 Vincent and Velkoff 2010
109 Nelson 2009
110 Myers and Pitkin 2009
111 National Research Council of the National Academies, Driving and the Built Environment 2009

Chapter 3. Environmental Consequences of Trends in Land Use,
              Buildings, and Vehicle Travel
Although development provides many social and economic benefits, it also comes at a cost.
Development has seriously degraded or destroyed many natural areas and caused significant growth in
driving—both of which have impacts on the health of critical environmental resources as well as on
people. These environmental consequences are particularly important because the effects of
development are long lasting and not easily reversible. As a result, the cumulative effects of
development decisions are important when considering the long-term health of the environment and

The research summarized in this chapter outlines how significant the impacts have been to the natural
environment: to critical habitat for plants and animals, to water resources, to air quality,  and maybe
most importantly, to the planet itself in the form of global climate change. This chapter also discusses
impacts that most directly affect human health apart from  the surrounding ecosystem: how the way we
build our communities influences levels of physical activity, affects levels of community engagement,
and affects the  risk of being injured or killed in a traffic crash. Many of the impacts discussed in this
chapter help point to potential solutions, including changes in how and where we  grow and develop our
communities, which are discussed in Chapter 4.

This chapter covers the following environmental and human health impacts of the built environment:

    1.  Habitat loss, degradation, and fragmentation.
    2.  Degradation and loss of water resources.
    3.  Degradation of air quality.
    4.  Heat island effect.
    5.  Greenhouse gas emissions and global climate change.
    6.  Health and safety.

3.1    Habitat Loss, Degradation, and Fragmentation

Habitat loss, degradation, and fragmentation are some of the most direct impacts of development on
previously undeveloped land. Construction of new buildings, roads, and other infrastructure often
destroys native vegetation. Landscaping in the remaining open  space with new lawns and non-native
plants often cannot serve the same ecological functions as the vegetation it  replaces. In addition to
direct habitat loss, development often fragments habitat, isolating patches of natural areas with
surrounding buildings and roads.

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

3.1.1  Effects of Habitat Loss

Habitat destruction and degradation contribute to the endangerment of more than 85 percent of the
species listed or formally proposed for listing under the federal Endangered Species Act.112 This loss is
critical because biodiversity is the foundational underpinning of ecosystems; the number and type of
plants and animals in an area determines the very structure and function of ecosystems across the
planet.113 Ecosystem functions cover a wide spectrum. The concept of ecosystem services describes the
benefits that we humans get from the natural world, including its plants, animals, microorganisms,  and
non-living components. Scientists have categorized ecosystem services into provisioning services of
things like food, fiber, and fresh water that are necessary for life, regulating services like pollination and
water purification, cultural services like recreation and education, and supporting services like
photosynthesis and nutrient cycling.114

Loss of natural areas affects all of the ecosystem services that they provide. However, not all natural
areas are created equal, and the impacts of development depend heavily on what type of ecosystem the
area supports. This section highlights two important types of ecosystems in the United States: wetlands
and forests.

Loss of Wetlands
Wetlands in particular have garnered considerable attention because of their ecological importance.
Wetlands are characterized by soil types, plants, and animals that occur in areas regularly saturated with
water. They vary widely depending on
local geography, climate, hydrology,
and water chemistry, among other
factors, and occur in diverse
ecosystems all over the world.
Although they tend to occur in small
patches throughout an ecosystem, the
world's largest wetlands include the
bottomland hardwood forests, swamps,
and marshes of the Mississippi River
basin (41,700 square miles) and the
marshes and meadows of the  Prairie
potholes (24,000 square miles).115
Wetlands perform invaluable ecological
functions. The rate of organic matter
production in wetlands is among the
Exhibit 3-1: Lily Pad Lake, Yellowstone National Park, Wyoming. A
shallow, open lake covered in water lilies supports a variety of wetland
plants along with many species of birds, fish, and other wildlife.
Photo source: EPA.
   Wilcove, et al. 1998
  ' Hassan, Scholes, and Ash 2005
  1 Hassan, Scholes, and Ash 2005
  'Keddy 2010

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

highest of any ecosystem. They mitigate flooding and damage from erosion, wind, and waves; facilitate
soil formation; provide rich feeding grounds and habitat for water life, waterfowl, mammals, and
reptiles; help regulate atmospheric carbon dioxide and methane levels; help maintain the global
nitrogen cycle; and improve water quality by removing excess nutrients and some chemical
contaminants.116 These myriad ecosystem services cannot be easily replaced. For example, while
constructed levees can serve as storm protection, they cannot provide the host of other ecosystem
services that coastal wetlands do.117

In the late 1700s, the lower 48 states had an estimated 221 million acres of wetlands.118 Less than half
those acres remain today.119 The annual wetland losses measured since the 1950s have decreased due
to protection under the Clean Water Act and restoration efforts, and wetland acreage even increased
between  1998 and 2004 (Exhibit 3-2). However, researchers estimate 13,800 acres of wetlands were lost
annually between 2004 and 2009, although the difference between the 2004 and 2009 national
estimates was not statistically significant. Development contributed to the loss of 128,570 acres, or 23
percent of the total loss between 2004 and 2009,120 much of which was offset by wetland
reestablishment and creation. However, the success of restoration efforts varies,121 and this inventory
does not  include information on the wetlands' quality or condition.

c (200,000) -
| (300,000) -
| (400,000) -

, •
(500,000) \tDo,uuu;
1950s-1970s 1970s-1980s 1980s-1990s 1998-2004 2004-2009
(hibit 3-2: Estimates of average annual net loss and gain of wetlands in the lower 48 states.
3urce: Dahl 2011, Figure 19, based on multiple sources.

In spite of an overall positive trend in national wetland acreage, results are not uniformly encouraging.
Coastal wetland restoration is often more difficult and more expensive than interior wetland
   Keddy 2010
117 Costanza, et al. 2008
118 Dahl 1990
119 Dahl 2011
120 Tree cultivation was the most significant cause of wetland loss (56 percent), and the remainder (21 percent)
was due to wetland conversion to deep, permanent water bodies.
121 Suding 2011

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
restoration, so restoration efforts generally offset fewer of the wetland losses along the coasts than in
other parts of the country.122 For example, between 1998 and 2004 when the country gained 32,000
acres of wetlands annually, coastal wetlands along the Gulf of Mexico declined by 61,800 acres annually,
and coastal wetlands along the Atlantic Ocean declined by 2,500 acres annually. Nearly one-quarter of
the freshwater wetlands lost along the coasts is attributed to urban and rural development.123

Loss of Forests
Forests, too, are important ecosystems in the United States. Among the many ecosystem services they
provide are helping to regulate the global carbon cycle and hence the rate of global climate change and
conserving our soil and water resources.124 For example, just over half of the nation's water supply
originates on forested land.125

Most of the forest loss in the United States occurred in the 17th to 19th centuries. Researchers have
estimated that forest covered just over 1 billion acres, or 46 percent of the land in the United States, in
1860—a figure that dropped to 759 million acres (34 percent) by 1907, a loss of almost 300 million
acres, predominantly to create cropland.126 Since 1907, forest cover in the United States has been
relatively stable. The U.S. Forest Service estimates that in 2007, the United States had 751 million acres
of forests.127
Although nationally the total amount of forest cover has been relatively stable, some regions have
shown significant losses. The
northeastern United States has
had a great deal of forest
regrowth on abandoned
cropland, while a  lesser amount
of regrowth has occurred in
Appalachia and around the
Great Lakes. However, other
parts of the United States
experienced significant declines
since the early part of the 20th
century, including western
states (particularly California and
Texas) and Florida (Exhibit
3-3).12S Most of the land newly
Exhibit 3-3: Change in forest area, 1907-2002.
Source: Ramankutty, Heller, and Rhemtulla 2010
   Stedman and Dahl 2008
  ' Stedman and Dahl 2008
  1 Hassan, Scholes, and Ash 2005
  ' U.S. Department of Agriculture Forest Service 2009
  'Smith and Darr 2004
  'Smith, Miles, etal. 2009
  ! Ramankutty, Heller, and Rhemtulla 2010

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

developed for urban expansion was previously forested, amounting to 4.7 million acres lost between
1973 and 2000.129

National statistics on forest cover also obscure other regional threats beyond outright loss. These
threats include changes in forest ownership leading to loss of active forest management, substantial
increases in forest fragmentation, and declines in overall forest quality due to factors such as more tree
deaths from insect infestation.130

3.1.2  Effects of Habitat Degradation

Managed Landscapes
A significant amount of development in the United States since the 1950s has occurred at relatively low
densities, with residential buildings surrounded by driveways, sidewalks, patios, lawns, and other
managed landscaping. In 2009, the median housing lot size was 0.27 acres, but more than 40 percent of
the lots were more than one-half acre.131 Many of these suburban landscapes support wildlife such as
deer, foxes, turtles, and snakes that are rare in more urban areas. However, the widespread
replacement of millions of acres of native vegetation with primarily non-native ornamental plants in
managed landscapes is a growing problem for the organisms that depend on native plants for food,
shelter, and places to rear their young.

The impact of a non-native species depends on its ecological context, and many non-native species
provide important ecological benefits.132'133 One fundamental role of plants in an ecosystem  is to create
food for herbivores that can transfer their stored  energy to higher-level predators. However,
homeowners and landscapers have often chosen  non-native species for their resistance to insects. In
fact, most insect species lack the physiological and behavioral adaptations needed to use non-native
plants for food. If ornamental plants cannot serve as food for the same number and diversity of
herbivores, the energy available for food webs decreases.134

Many studies have documented the negative effect that non-native plants can have on the abundance
and diversity of insect  herbivores. Many have used moths and  butterflies as surrogates for all insect
herbivores because information about their host  plants is relatively robust and their larvae are especially
valuable sources of food for many birds.135 A comparative study of suburban properties found that the
abundance and diversity of moths, butterflies, and breeding  birds was positively correlated with the
percentage of native grasses, wildflowers, and shrubs in the  landscape. For example, there were four
times as many moth and butterfly larvae and three times as  many moth and butterfly species on
properties planted with native ornamental plants than on properties with a mix of native and non-native
   Drummond and Loveland 2010
130 U.S. Department of Agriculture Forest Service 2011
131 U.S. Census Bureau, "American housing survey for the United States: 2009" 2010
132 Davis, et al. 2011
133 Simberloff 2011
   Tallamy and Shropshire 2009
135 Tallamy and Shropshire 2009

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
ornamentals.136 A literature review documents that native woody plants support three times as many
moth and butterfly species as introduced plants, while native woody plants used as ornamentals support
14 times as many moth and butterfly species as non-native ornamentals.137 In a study of planted garden
plots, non-native plants supported significantly fewer caterpillars of significantly fewer species than
native plants, even when the non-natives were close relatives of native host plants.138 Researchers
found similar results in a desert ecosystem. A study of neighborhoods in central Arizona showed that
native desert bird species exist in greater numbers in neighborhoods with desert landscaping designs
and in neighborhoods closer to large desert areas.139

Suburban lawns and landscaped areas have other ecological effects. Construction activity for
development tends to compact soil, reducing the ability of air and water to move through it. These
changes ultimately reduce soil biodiversity by reducing soil microbial biomass, enzymatic activity, soil
fauna, and ground flora.140 Reduced infiltration also limits the amount of precipitation the land can
absorb (see Section 3.3), increases risk of flooding, and reduces ground water recharge.141 One study
showed that residential construction activity in north central Florida reduced the infiltration rates in
yards covered with turf by 70 to
99 percent relative to nearby
natural forest.142 Another study
in Pennsylvania found that the
infiltration rate of lawns of
more recently constructed
homes (since 2000) was
69 percent lower than for lawns
of older homes, and 73 percent
lower than for agricultural sites,
possibly due to changes in
construction practices and/or
changes over time as
vegetation becomes more
established.143 Lawn and
landscaping irrigation can also
be a major drain on water
resources.  Fertilizer, if
Exhibit 3-4: Lawn and landscaping. Managed parks and residential lawns can
create large areas with little ecological function that require large amounts of
water, chemicals, and energy for mowing.
Photo source: this lyre lark (derya) via flickr.com
  ' Burghardt, Tallamy, and Shriver 2008
  ' Tallamy and Shropshire 2009
  ! Burghardt, Tallamy, and Philips, et al. 2010
  ' Lerman and Warren 2011
   Nawaz, Bourrie, and Trolard 2013
  1 Gregory, et al. 2006
  " Gregory, et al. 2006
  ' Woltemade 2010
  ' Haley, Dukes, and Miller 2007

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

applied when not needed, can lead to excess phosphate and nitrate in local water bodies.145 Many lawns
and landscapes are also treated with insecticides and herbicides that can eradicate native plants and
insects. Finally, mowing uses fossil fuels.146

Developed areas, even those developed at relatively low densities, thus fundamentally change the food
and other resources available to species in an ecosystem. For nearly all plants and animals, species
diversity declines with increases in the amount of impervious surface, road density, time since
development, human population density,  and building density.147 Animal species that do well in urban
environments tend to be generalists that can adapt to available food resources, and they tend to have a
set of common behavioral characteristics:  they are less wary of people, they are more aggressive
towards members of their own species, and they have altered seasonality (e.g., hibernation behavior).148
The species composition of both plants and animals within cities tends to be more similar than would be
expected based on species found in nearby natural areas due in part to the similar pressures wildlife
faces in developed  areas and the dominance of non-native species.149'150

Invasive Species
Researchers estimate approximately 50,000 non-native plant and animal species have been introduced
into the United States, and about 5,000 of these have become established in natural ecosystems, most
replacing several native species.151 Some established, non-native species spread widely or quickly and
become invasive, causing ecological or economic harm or harming human health.152 Invasive species are
at least in part responsible for the listing of about 42 percent of the species that are threatened or
endangered.153 An analysis of nearly 300 publications on the impacts of invasive species across the world
concluded that invasive species tend to harm species and community health, especially for plants.154

A study of the change in plant species in Marion County, Indiana, illustrates the problem  on a smaller
scale. Researchers compared historical records of wild plant species from before 1940 with the species
found in surveys conducted  between 1996 and 2009. Although the overall number of species remained
relatively constant, the number of native plant species declined by 2.4 per year. Researchers found
10 percent fewer native species than existed in the county less than a century before.  Many high-value
wetland plants were lost and were replaced with invasive shrubs that escaped from cultivation.155
145 Brown and Froemke 2012
146 Hosteller and Main 2010
147 Pickett, et al. 2011
148 Pickett, et al. 2011
149 Pickett, et al. 2011
150 McKinney 2006
   Pimentel, Zuniga, and Morrison 2005
152 National Invasive Species Council n.d.
153 Pimentel, Zuniga, and Morrison 2005
154 Pysek, Jarosik, et al. 2012
155 Dolan, Moore, and Stephens 2011

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
Invasive species threaten more than
ecosystems. They can also directly
affect human health. For example,
kudzu infestations in Madison  County,
Georgia, increase nitrogen cycling in
soils, which can increase emissions of
nitric oxide, an ozone precursor, by
more than 100 percent.156 A review of
the ecological and human health effects
of invasive species documents a range
of impacts, including:

    •   Human disease—For example,
       the tiger mosquito is a vector
       for pathogens that cause
       dengue fever, yellow fever, and
    •   Toxins in human food—For
       example, honey made
       exclusively from the herb
       Salvation Jane (Echium plantagineum) contains toxic levels of pyrrolizidine, which can cause liver
    •   Allergies—For example, pampas grass causes pollen allergies.
    •   Injury—For example, leaves of common cordgrass (native to the U.S. Atlantic coast but invasive
       on the U.S. Pacific coast) can cut skin, and the rugosa rose creates thorny thickets.
    •   Contamination—For example, the droppings of excessive numbers of Canada geese can
       contaminate soil and water.157

3.1.3   Effects of Habitat Fragmentation

Landscape modification, whether for agriculture or development, not only destroys native vegetation in
the area modified, but also harms what native vegetation remains because of nearby increased land-use
intensity.158 A 2007 literature review shows landscape modification and habitat fragmentation
negatively affect virtually all taxonomic groups, including birds, mammals, reptiles, amphibians,
invertebrates, and plants, and  is a severe threat to global biodiversity.159 The edges of forests, meadows,
and other natural areas can have different characteristics than the more central areas. The amount of
sunlight and moisture, temperature,  humidity, wind speed, and soil nutrients all differ, which leads to
Exhibit 3-5: English Ivy is native to Europe and Western Asia. In the
United States, it is a common landscape plant but also an invasive
species. Uncontrolled, the vine can overtake stands of trees.
Eventually the weight of the vine can topple trees or kill them by
blocking sun from the tree's leaves. It can also completely cover a
forest floor, outcompeting other understory plants.
Photo source: English Ivy Nancy Fraley, USDI National Park Service,
   Hickman, et al. 2010
   Pysek and Richardson 2010
  1 Fischer and Lindenmayer 2007
   Fischer and Lindenmayer 2007

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

differences in the species of plants and animals found there and their patterns of competition,
predation, and parasitism. In general, these changes harm native ecosystems,160 particularly as habitat
becomes ever more fragmented and the proportion of it with these effects increases. Development is a
common cause of habitat fragmentation. A study of how forest cover varies with different levels of
development in New England suggests that development generally begins in a few small patches. As
development increases, the number of communities increases, but only up to a certain level, beyond
which they begin to coalesce into larger towns and cities. However, fragmentation of forested land
continues increasing even beyond this point, possibly due to increasing road density.161

The ecological effects of habitat fragmentation have been widely studied. A review of the literature
shows that while the total amount of habitat and its quality have a greater and better documented
effect on the number of plant and animal species in an area than habitat fragmentation/62 the effects of
fragmentation are wide ranging and significant. A quantitative review of studies shows that habitat
fragmentation decreases the genetic diversity of plant populations,163 which can reduce their ability to
adapt to changing conditions, raising their risk of extinction.164 Fragmentation often decreases
population  size and increases population density, reducing  availability of resources (e.g., food and
nesting sites) and leading to home-range overlap and elevated relatedness within populations. All of
these changes affect  how members of a single species interact among themselves, including mating
patterns, often reducing reproductive success. These changes also affect how different species interact
with each other, influencing predator-prey, host-parasite, and competitor interactions.165 Animals can
have difficulty moving around to find food or mates and escape from predators. Habitat fragmentation
also disrupts large-scale  animal movements such as migrations or range changes that could be necessary
to adapt to climate change.166

Research suggests habitat fragmentation could also directly affect human health through its effects on
disease vectors and their hosts. For example, as fragmentation increases, mammalian species diversity
decreases, and some tick hosts decline  or disappear while mice, which are relatively good reservoirs for
the bacterium that causes Lyme disease, tend to dominate.  In such areas, modeling suggests that human
exposure to Lyme disease would be higher.167
160 Fischer and Lindenmayer 2007
161 Coles, et al. 2010
162 Di Giulio, Hoderegger, and Tobias 2009
163 Aguilar, et al. 2008
164Spielman, Brook, and Frankham 2004
165 Banks, et al. 2007
   Fischer and Lindenmayer 2007
167 LoGiudice, et al. 2003

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

3.1.4  Effects of Roads: Combined Effects of Habitat Loss, Degradation, and Fragmentation

The direct and indirect ecological effects of roads are so significant that their study has emerged as a
specific field called road ecology.168 Roads, from  local streets to highways, are a large component of the
built environment, and they contribute to habitat loss, degradation, and fragmentation.

Roads have numerous impacts on the environment. Precipitation landing on roads can pick up heat and
pollutants and travel quickly to water bodies, affecting water quality and causing erosion and
subsequent changes to stream channels instead  of replenishing ground water where it lands (see
Section 3.2). A whole host of chemical pollutants arise from road construction, maintenance, and use,
including pesticides, deicing salts, hydrocarbons, asbestos, lead, cadmium, copper, carbon monoxide,
nitrogen oxides (NOX), volatile organic compounds (VOCs), sulfur dioxide, particulates, methane,
benzene, butadiene, and formaldehyde. Noise near roadways can be significant. Finally, roadsides tend
to be windier, hotter, dryer, sunnier,
and dustierthan the surrounding
natural habitat. The microclimatic
effects of even narrow roads
determine the plants and soil
macroinvertebrates that can survive
there. Even birds, amphibians,
reptiles, and mammals are affected,
contributing to a decline in  overall
species richness near roadways.169

Roads affect wildlife in several ways.
First, roads directly destroy
habitat.170 Second, roads contribute
significantly to habitat
fragmentation171 and block
movement for many animals.
Finding food, mates, and breeding
sites can be more difficult or even impossible. These limitations affect the ability of populations to breed
with one another, reducing the overall genetic diversity.172 Third, roads facilitate the spread of non-
native and invasive species. Travel along roads helps to disperse seeds, and disturbed areas along
roadsides provide long corridors of uninterrupted habitat in which weeds can thrive with little
competition from woody plants.173 Finally, roads are responsible for the deaths of large numbers of
Exhibit 3-6: Road through natural area. Vermont Route 17 is a heavily
traveled road that bisects Camels Hump State Forest, creating a hazard
for wildlife and fragmenting habitat.
Photo source: EPA
   Forman, Sperling, et al. 2003
  ' Coffin 2007
  ' Coffin 2007
   Coffin 2007
  " Di Giulio, Hoderegger, and Tobias 2009
  ' Coffin 2007

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

animals174 (and humans; see Section 3.7.3). Animals that move slowly or that regularly need to cross a
road are particularly affected. For other species, the road is an appealing travel corridor, leading to more
animals being killed by vehicles. For example, in areas with heavy snow cover, wildlife often favor
plowed roads for travel, increasing their risk of being hit by a vehicle. The Federal Highway
Administration estimated that there are 1 to 2 million collisions between vehicles and large animals per
year.175 These collisions cause about 200 human deaths and 26,000 human injuries per year, and  they
almost always kill the animal involved. Road mortality is a major cause of death for 21 animals on the
federal threatened or endangered species list, including the Florida panther, red  wolf, American
crocodile, California tiger salamander, and Florida scrub jay.176

Many studies have found that species density tends to increase as distance from  roads increases
because many species cannot survive along road edges.177 Researchers have attempted to define and
quantify the zone of land  around roads that the road system directly affects ecologically. A study of a
Massachusetts suburban highway found that this road-effect zone tends to be asymmetric and variable
along its length, but in general, the  effects of the factors studied extended more  than the length of a
football field or more than 328 feet (100 meters) from the road.178 Some effects  occurred more than
0.62 miles (1 kilometer) from the road. For example,  moose preferred this area for travel, while
grassland birds avoided it. Overall, the impact zone averaged about 0.4 miles (600 meters) wide. As
noted in Section 2.3.1, another analysis found that more than 50 percent of all land in the United States
would fall within this zone.179 However, an attempt to estimate the amount of land in the United  States
directly affected ecologically by roads after accounting for the asymmetric and variable shape of the
road-effect zone concluded that this zone covered 20 percent of the land area in the  United States as of

3.2   Land Contamination

Past industrial activity has left a legacy of soil and water pollution at former industrialized sites.
Thousands of these potentially contaminated properties, or brownfields,181 are located in densely
populated neighborhoods, often near places where residents gather and children play. Many of these
sites are near rivers that once served  as valuable transportation corridors. The juxtaposition of toxic
174 Coffin 2007
175 Federal Highway Administration 2008
   Federal Highway Administration 2008
177 Coffin 2007
   Forman and Deblinger 2000
179 Riitters and Wickham 2003
180 Forman 2000
181 Brownfields are defined as "real property, the expansion, redevelopment, or reuse of which may be
complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant" in Public
Law 107-118 (H.R. 2869) "Small Business Liability Relief and Brownfields Revitalization Act" signed into law January
11, 2002.

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
chemicals, human activity, and
sensitive environmental habitats can
lead to a range of problems,
including compromised human and
environmental health.

Reliable information on the number
of brownfields in  the United States is
scarce. A 2008 survey of 188 U.S.
mayors yielded an estimate of
nearly 25,000 brownfield sites
among their cities.182 In 2004, EPA
estimated that between 235,000
and 355,000 sites in the United
States were contaminated with
hazardous waste  and petroleum
products.183 An analysis of more
than 1,400 New York and Texas
properties in  state voluntary
cleanup programs suggested that commercial areas have as many potentially contaminated sites as
former industrial  areas.184 The study also revealed that areas that have experienced more recent rapid
economic growth have as many potentially contaminated sites as older industrial areas. Another study
estimated brownfield acreage in two cities based on official lists of contaminated properties and land
use history that suggested a high probability of contamination.185 The researchers estimated that
Atlanta has 3,244 acres of brownfields out of 84,750 total acres, covering almost 4 percent of its land
area.  Out of 52,458 total acres, Cleveland has 3,701 acres of brownfields covering more than 7 percent
of its  land area. Similarly, state,  local, and federal inventories indicate that 1,027 properties in the city of
Milwaukee are brownfields, constituting 7.5  percent of its land area.186

Poor and minority neighborhoods often have a disproportionately high  number of brownfield
properties. For example, a study of brownfields in the Detroit region found that census block groups
located within a half-mile of a brownfield were 58 percent African-American with a median income of
$34,177, while block groups located more than a half-mile from a brownfield were 21 percent African-
American with a median income of $55,687.  The effects  of income were independent of the effects of
Exhibit 3-7: Weirton Steel, West Virginia. As the steel industry declined in
much of the country, many mills were completely or partially abandoned,
leaving behind large, often polluted sites. Because many towns were built
around steel mills, these sites are often in a central location with easy rail,
highway, and/or river access, making them important locations for
redevelopment in many communities.
Photo source: Bob Jagendorf via flickr.com
   United States Conference of Mayors 2008
   EPA, Cleaning up the Nation's Waste Sites 2004. This estimate includes Superfund program sites, Resource
Conservation and Recovery Act Corrective Action sites, Underground Storage Tank sites, Department of Defense
installations, Department of Energy sites, other civilian federal agency sites, and state and private party sites in
mandatory cleanup and brownfields programs.
184 Page and Berger 2006
185 Leigh and Coffin 2005
186 McCarthy 2009

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

race.187 A similar study of Milwaukee found that census tracts with an above-average percentage of
African-Americans had more than 25 percent more brownfields per square mile than census tracts with
a below-average percentage of African-Americans; census tracts with an above-average percentage of
Hispanics had twice the number of brownfields per square mile as census tracts with a below-average
percentage of Hispanics; and census tracts with an above-average percentage of people below the
poverty level had nearly three times as many brownfields per square mile as census tracts with a below-
average percentage of people below the poverty level.188

3.3    Degradation and Loss of Water Resources
                                                                           189 •
Most developed land in the United States was originally grassland, prairie, or forest.   The replacement
of these natural ecosystems with buildings, roads, and other infrastructure has several impacts on water
resources and water quality. EPA collects reports from states on the results of water body assessments
in the Watershed Assessment, Tracking & Environmental Results (WATERS) database. Exhibit 3-8 shows
the probable source of impairment for different types of assessed water bodies.

Most sources of impairment are directly or indirectly related to the built environment. However, the
category labeled "urban-related runoff/stormwater" is the source most directly connected to the
amount of impervious cover on the landscape and thus most directly influenced by where and how we
build our communities. Urban-related stormwater is thought to be responsible for the impairment of
858,186 acres of lakes, reservoirs, and ponds and 51,548 miles of rivers and streams, among other types
of assessed waters (see Exhibit 3-8). These estimates are likely low because the majority of U.S. waters
have not been assessed: only 45 percent of lakes, reservoirs, and ponds; 27 percent of rivers and
streams; and 37 percent of bays and estuaries have  been assessed. In addition, stormwater discharges
come from  numerous sources and are episodic and diffuse, making them difficult to identify. Thus,
stormwater is thought to be underreported as a source of impairment for many assessed waters.190 In
fact, "other," "unknown," and "unspecified point source" are among the largest categories of probable
source groups.

The hydrology of most urban  systems is highly modified due to  development and flood prevention.
Storm drains, water mains, wastewater sewers, and other water infrastructure control the movement of
water on the surface and underground throughout many developed areas.191 Even the natural stream
network is often forced into underground pipes that are fed by storm drains.192 The natural hydrologic
187 Lee and Mohai 2011
188 McCarthy 2009
189 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
190 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
191 Price 2011
192 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009

                                Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

system has a set of consistent responses to such changes that affect its hydrology, geomorphology,
stream pollution and nutrient levels, and aquatic life.193
Probable Source Group
Atmospheric Deposition
Commercial Harbor and Port
Ground Water
Habitat Alterations (not Directly
Related to Hydromodification)
Land Application/Waste Sites
Land Application/Waste Sites/Tanks
Legacy/Historical Pollutants
Military Bases
Municipal Discharges/Sewage
Recreation and Tourism (Non-
Recreational Boating and Marinas
Resource Extraction
Silviculture (Forestry)
Unspecified Nonpoint Source
Urban-Related Runoff/Stormwater
Total Impaired
Total Assessed
Total Not Assessed
Size of Assessed Waters With Probable Sources of Impairments
Rivers and


and Ponds

Bays and





Ocean and
Near Coastal











Great Lakes





Great Lakes
Open Water





Exhibit 3-8: Probable sources contributing to water quality impairments nationally, 2012. EPA classifies each cause of
impairment reported by states into one of the listed causes of impairment for reporting purposes. Blank cells indicate no
states reported anything for that source group for that water type group. Cells with zero values indicate one or more states
did report that source, but the total reported was less than 0.5. This table reports the most currently available information as
of September 2012, which varied by state.
Source: EPA, Watershed Assessment, Tracking & Environmental Results n.d.
   Walsh, etal. 2005

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

3.3.1  Effects of Development on Stream Hydrology

Development causes fundamental changes to the water (or hydrologic) cycle, the pattern of movement
of water on, above, and below the earth's surface through processes such as evaporation, precipitation,
and infiltration.

The first effects occur once vegetation is removed from the landscape. Removing vegetation decreases
the amount of precipitation that returns to the atmosphere through evaporation from the earth's
surface and transpiration from plant surfaces (together called evapotranspiration). In arid regions of the
country where most precipitation is evapotranspired, this reduction alone has a particularly significant
impact on the water cycle.194 However, in developed areas, not only is the amount of vegetation
diminished, sometimes significantly or even entirely, but impervious surfaces such as pavement and
rooftops increase, and the amount of water that runs off the surface of the land increases.

Increased runoff in turn has several effects on the water cycle. First, it reduces the amount of water that
recharges underground water storage areas and moves through subsurface pathways. These ground
water channels largely sustain streams, so their reduction can lead to reduced flows during dry periods.
Second, increased runoff makes floods more frequent and severe during wet periods, as water that
would normally soak into the ground near where it lands instead cannot infiltrate.195

Increased runoff is not only a problem of increased water quantity, but also of increased water speed  as
it flows. An increased quantity of water moves faster, reaches peak flow more quickly after precipitation
begins, and flows for a longer period of time—all of which increase erosion and flood risk.196 In addition,
flow characteristics affect aquatic species whose behavior is generally adapted to a particular pattern  of

Not only does the amount of runoff entering water bodies increase as impervious cover increases, the
temperature of the water tends to increase as well. Many impervious surfaces are dark. They transfer
the heat they have absorbed to the water that lands on or runs over them. Warmer water holds less
oxygen for aquatic species and can disrupt mating, reproduction, foraging, and predator escape.198

Changes in the water cycle  due to development can be substantial. For example, in a study of two
similar areas in the Piedmont region of North Carolina over five years and seven months, one area
remained as forest and agricultural fields while the other was developed as a residential subdivision of
32 single-family homes, which resulted in 53 percent impervious cover. In the area that was developed,
the volume of runoff was 68 percent greater, and the ratio of runoff to rainfall was 2.75 times that in the
undeveloped area. Much of the difference is accounted for by decreased shallow, subsurface flows in
the developed area. One day after most rain events and two days after large rains (more than  50
   National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
195 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
196 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
   National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
198 Frazer 2005

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

millimeters), the developed area had no stormwater remaining to discharge. The undeveloped area
discharged 25 percent of the total precipitation after this period because it had been able to hold the
water and discharge it more slowly.199

Changes in the water cycle due to development are also widespread. An analysis of streamflow
alterations at 2,888 stream monitoring stations across the United States found that 86 percent differed
in some way compared to a nearby reference location in a relatively undisturbed area. Moreover, the
greater the degree of stream flow alteration, the less able a stream was to support and maintain life
based on multiple measures of community health for both fish and macroinvertebrates.200

Although many impacts of urbanization are consistent across regions, particular impacts can also be
unpredictable. For example, although decreased  infiltration often  reduces the amount of precipitation
that flows through underground pathways, in many urban areas, this baseflow can actually increase.
Water distribution pipes, particularly those in older cities that might be in operation beyond their
expected useful life, can leak large amounts of water. Irrigated lawns and other areas can also increase
baseflow beyond what would occur naturally because underground pipes might carry the water from
another watershed.201

Regional differences across the country also occur. An analysis of four large hydrologic regions of the
United States measured the correlation between 10 hydrologic variables and the proportion of the
watershed area that is urban.202 Exhibit 3-9 shows the statistically  significant results, revealing that
impacts of development on stream hydrology are diverse and can  vary across geographic regions.203
Peak flow
Minimum daily streamflow
Days per year with no streamflow
Duration of moderately high flows
Flow variability
               Exhibit 3-9: Effects on streams of increasing development in different regions of the
               United States. Results were not statistically significant in cells marked with "—".
               Source: Poff, Bledsoe, and Cuhaciyan 2006

3.3.2   Effects of Development on Stream Geomorphology

Geomorphology is the arrangement and characteristics of landforms, including stream channels, ridges,
hill slopes, and flood plains. Most natural stream channels have a complex structure that creates
variation in flow (and thus habitat) along the channel. A riparian zone occupies the transition between
   Line and White 2007
200 Carlisle, Wolock, and Meador 2011
201 Price 2011
   The authors used data from the U.S. Geological Survey National Land Cover Database to classify areas into one
of three classes: least disturbed, including forests, grasslands, wetlands, open water, and bare rock; agriculture;
and urban, including low- and high-intensity mines, residential areas, and other areas planted with grasses such as
parks or golf courses.
203 Poff, Bledsoe, and Cuhaciyan 2006

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
the stream channel and upland
areas. In humid regions, shallow
ground water forms flow paths
to streams. These areas can
support anaerobic microbial
activity that provides a sink for
inorganic nitrogen and reduces
nitrate loads flowing to the
stream. In arid regions, riparian
areas can be the only areas in
the watershed that have
sufficient moisture to  support
the vegetation that provides
critical habitat and other
ecosystem services.204 Flood
plains, which are periodically
inundated, are integral parts of
river systems.
                       Exhibit 3-10: Stream bank erosion from stormwater. Heavy flows have
                       scoured the bank of Whiteley Creek in Garards Fort, Pennsylvania, leaving
                       roots exposed, toppling trees, and increasing the amount of sun falling on the
                       stream, which raises the water temperature.
                       Photo source: EPA
The hydrologic changes due to development cause several visible geomorphologic changes to stream
systems. Increased flow washes out woody debris and uproots trees and other vegetation, which
destabilizes stream channels and can harm aquatic habitat. Even if forest regeneration occurs, natural
rates rarely compensate for the losses. In many developed areas, forest regeneration cannot occur at
all.206 Erosion can eventually lead to stream  bank collapse, which deepens and widens channels and can
shift normal flow levels many feet below their original level.207 Such a change in channel geomorphology
can lower ground water levels nearby. With lower ground water levels, subsurface water flows to the
channel only through deeper paths that lack the organic material found at the surface. Without this
organic material, which supports anaerobic  microbial activity that reduces nitrate, additional nutrients
flow to the stream.208 Such hydrologic changes are due to increases in impervious cover in developed
areas, but in many cases, people modify stream channels directly, straightening and lining them to
increase capacity, reduce flooding risk, and fix the position of the stream.209

Several  studies have documented changes in channel geomorphology with development,210 although
the relationship is complex. For example, a study of 30 streams in nine U.S. metropolitan areas found
that watershed-scale indicators of stream habitat quality were associated with the percentage of
   National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
  ' Booth and Bledsoe 2009
  5 Booth and Bledsoe 2009
  ' National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
  ! National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
   National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
  5Jacobson 2011

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

impervious surface only in some metropolitan areas and environmental settings.211 This and other
studies212 found that multiple factors influence how stream channels respond to development, including
climate, hydrology, slope, vegetation, and the presence of bedrock. In addition, historical alterations of
the drainage network for stormwater management, grade control, bank stabilization, and other reasons
continue to influence stream channels, complicating interpretation of studies that consider only the
most recent alterations.

3.3.3  Effects of Development on Water Pollution and Nutrients

Most small, natural streams have very low levels of toxic chemicals; relatively low levels of dissolved
solids such as calcium, nitrate, phosphorus, iron, and sulfur; and relatively low levels of suspended solids
such as silt, algae, and organic debris. Development increases their concentrations in water bodies
through stormwater  runoff, which picks up lawn fertilizer  and pesticides,  pet waste, trash,  pollution
from vehicles and pavement materials, and chemicals from industrial and commercial activities. When
stormwater infiltrates soil, the soil can immobilize many of the pollutants or absorb them until they are
broken down. Unless stormwater soaks into the ground or is otherwise treated, it will transport
pollutants it picks up to a nearby water body. Pollution also reaches water bodies directly from the air,
either settling to the  ground as dust or falling in rain or snow, and from direct discharges (e.g., from
leaking sanitary sewer and drinking water distribution systems or industrial  wastewater). Common
pollutants found in stormwater include trash, sediment, nutrients,213 bacteria, metals, pesticides, and
other chemicals.214'215

The National Stormwater Quality Database compiles data  collected since the early 1990s from nearly
200 municipalities regulated under EPA's stormwater permit program. All samples include  information
on land use at the collection site, allowing comparisons of water quality across land use types. Statistical
analyses  of the data show significant differences in pollution levels across land uses for nearly all
pollutants measured:216

    •  Open space shows consistently low concentrations of all pollutants and other constituents
    •  Residential areas have the highest concentrations of dissolved and  total phosphorus and
       relatively high concentrations of fecal coliform.
211 Fitzpatrick and Peppier 2010
212 Poff, Bledsoe, and Cuhaciyan 2006
   Nutrients (nitrogen and phosphorus) are necessary for living plants and animals. However, excess quantities in
our air and water cause environmental and human health problems, including massive overgrowths of algae that
can be toxic to humans and can consume so much oxygen in water bodies that other organisms are unable to
   National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
215 Polycyclic aromatic hydrocarbons are chemicals that could potentially cause health problems at high
concentrations. More information about them is available at
www.atsdr.cdc. gov/toxfaqs/tf.asp?id=121&tid=25#information.
216 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
  Exhibit 3-11: Road salt can contaminate surface and ground water.
  Rain or melting snow will carry road salt dropped from a truck in
  Dickerson, Maryland directly into the adjacent stream where the
  resulting water chemistry changes can harm fish and wildlife. Road
  salt can also contaminate drinking water sources and pose health risks
  to people.
  Photo source: EPA
                                                               •   Highway drainage has the
                                                           highest concentrations of total
                                                           suspended solids, chemical oxygen
                                                           demand (an indirect measure of the
                                                           amount of organic compounds
                                                           present), oil and grease, and ammonia.
                                                           Roads and parking lots can account for
                                                           as much as 70 percent of the total
                                                           impervious cover in the most urban
                                                           areas and can easily capture pollution
                                                           from vehicles.

                                                           An analysis of stream-bed sediment at
                                                           98 sites across seven metropolitan
                                                           regions found contaminants at all sites,
                                                           and the concentration tended to
                                                           increase with increasing development
                                                           of the area around the site.217
                                                           Nevertheless, the patterns of pollution
are quite irregular across developed areas, so correlations between measures of development such as
the percentage of impervious cover are generally weak.218 A study of 15 streams near Melbourne,
Australia, suggests that a more important variable than the percentage of impervious cover and one
with a stronger correlation with pollutant patterns is the amount of impervious area that is directly
connected to a stream by pipes or lined drains, also known as effective impervious area.219 Precipitation
falling on this type of impervious area is carried directly to streams without an  opportunity to infiltrate
into the ground.

Prior land use history can help explain why correlations between levels of development and levels of
pollution are weak. For example, a study of six different metropolitan areas of the United  States found
that insecticide concentrations increased with increasing development in all six areas. However, results
were less consistent for nutrients, sediment,  sulfate, and chloride.  In  places where development
occurred on what had been predominantly forestland or in other naturally vegetated areas, measures of
increasing development were generally associated with  increasing  chemical concentrations. The effects
of development were less clear in places where it occurred on land that was already stressed from
agriculture, large-scale movement and storage of water, or inflow of relatively saline ground water.220 A
later analysis showed that measurements of nitrogen, phosphorous, chloride, and pesticides not only
  Moran, et al. 2012
  ! Booth and Bledsoe 2009
  ' Hatt, et al. 2004
  'Sprague, et al. 2007

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

tend to increase as naturally vegetated areas are developed, but they also become more variable as
water quality fluctuates with seasonal activities such as road salting.221

Although correlations can be difficult to detect along a gradient of development, differences between
developed and undeveloped areas are prevalent and can be striking. For example, a study of copper,
lead, and zinc in samples from storm events in five California watersheds between 2000 and 2005 found
that their mean concentrations during storm events and their total loadings per watershed area were
significantly greater—often by more than an order of magnitude—in developed than in undeveloped
watersheds. The differences were likely largely attributable to stormwater runoff from industrial areas
in the developed watersheds.222 Even strictly residential development can have large impacts. The study
discussed in Section 3.3.1 of two similar areas, one undeveloped and one developed as a residential
subdivision in North Carolina, found that the amount of sediment exported from the developed area
was 95 percent greater and the amount of nitrogen and phosphorous exported was 66 to 88 percent

Development affects not only surface water, but ground water as well. Many studies of ground water
quality do not distinguish between industrial, commercial, and residential land uses. However, ground
water in developed areas tends to show levels of major ions (e.g., calcium, chloride, nitrate, sodium, and
sulfate), pesticides, VOCs (e.g., from degreasers, use in dry cleaning, or use in septic systems), and trace
elements (e.g., boron, copper iron, and manganese) at concentrations well above levels found in
undeveloped areas.224 For example, a study of how land use affects water quality of an aquifer in  east-
central Minnesota found that sewered residential and commercial or industrial areas had higher
concentrations of total dissolved solids—including calcium, potassium, sulfate, and magnesium-
relative to agricultural, unsewered residential, or undeveloped areas.225 Unsewered residential areas
had higher concentrations of boron, chloride, and nitrate. Researchers found VOCs in all samples  from
commercial or industrial areas and in about half of the samples from sewered residential areas. Samples
taken over a four-year period suggested that when an undeveloped area becomes residential, or  an
unsewered community is sewered, water chemistry changes rapidly. The data also suggest that prior
contamination in older residential and commercial areas might be gradually improving due to cleanup
and pollution  prevention programs.

An assessment of 55 VOCs in about 3,500 domestic and public drinking water wells across the United
States found that,  before any treatment, about 20 percent of samples covering 90 out of 98 aquifers
contained one or more contaminants at concentrations equal to or greater than 0.2 micrograms per
liter, although only Ito 2 percent of samples had concentrations known to be a potential health
221 Beaulieu, Bell, and Coles 2012
222Tiefenthaler, Stein, and Schiff 2008
223 Line and White 2007
224 Trojan 2005
   Trojan, Maloney, et al. 2003. Samples were collected from wells set 1 meter into the aquifer. At least 90 percent
of a 100-meter area that drains to each well consisted of a single land use.

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
concern.226 More than 50 percent of samples contained levels of contamination at concentrations equal
to or greater than 0.02 micrograms  per liter, indicating that although concentrations do not yet raise
human health concerns, VOCs are widespread in U.S. aquifers. The most frequently detected
compounds included solvents, refrigerants, a gasoline additive, and a gasoline component. The amount
of developed land was one of several factors commonly associated with detection.

Pesticides are also common contaminants in both ground water and surface streams. A national
assessment of untreated water samples from 186 stream sites and 5,047 wells found that 55 percent of
shallow ground water and 97 percent of stream samples in developed areas contained pesticides,
compared to 29 percent of ground water and
65 percent of stream samples in undeveloped
areas.227 While none of the samples in undeveloped
areas exceeded concentrations known to raise
human health concerns, 5 percent of ground water
and 7 percent of stream samples in  developed areas
did exceed such levels. About a quarter of pesticide
applications in the United  States are for non-
agricultural use around homes; in gardens, parks, and
golf courses; and along roads. Five herbicides and
three pesticides generally  used for non-agricultural
purposes were among the most frequently detected
3.3.4   Effects of Development on Aquatic Life

Although all types of water bodies are affected, most
research focuses on streams, which often flow
through a range of land use types and so allow
relatively straightforward assessment of how various
levels of development affect aquatic life. The impacts
of watershed development, including increased
pollution and temperature  and altered channels and
flow regimes, reduce the quantity, quality, and
diversity of stream habitat for aquatic life.228 Much of
the aquatic life in streams is adapted to a particular
Exhibit 3-12: Mayfly. Mayflies live just a few days as
adults but spend months or even years as larval
nymphs in freshwater streams or ponds. They are a
favorite food for fish and other aquatic predators.
They require water with a neutral pH and high levels
of dissolved oxygen, and they cannot tolerate
pollution, making them important water quality
Photo source: Andy Nelson via flickr.com
   Zogorski, et al. 2006
227 Gilliom, et al. 2006. In this study, land classified as urban contains more than 25 percent urban land and less
than or equal to 25 percent agricultural land. Land classified as undeveloped contains less than or equal to
5 percent urban land and less than or equal to 25 percent agricultural land. Land classified as agricultural land
contains more than 50 percent agricultural land and less than or equal to 5 percent urban land. All other
combinations are classified as mixed.
228 Booth and Bledsoe 2009

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

type of stream bed and flow pattern and cannot survive changes caused by frequent periods of high
flow that scour the stream bed, removing habitat used as a temporary refuge from the high flow. These
changes tend to favor certain types of species—those that have high reproductive potential, are
opportunistic, eat a wide variety of foods, and tolerate chemicals.229'230

An index of biological integrity is often used to capture the net impact on biological communities of
multiple, diverse stressors. A study of three streams in the upper Piedmont region of South Carolina
experiencing different levels of land development found that, as the amount of land disturbance
increased, impervious cover, stormwater runoff, and total suspended solids associated with storm
events increased, while habitat and an index of biological  integrity declined.231

3.3.5  Levels of Development at Which Effects Are Apparent

The level of development at which negative effects first begin to appear has been the focus of much
scientific study, and it has been widely debated whether any threshold exists  below which effects are
not detectable. Several recent studies support the idea that if such a threshold exists, it is at very low
levels of development. A study of nine U.S.  metropolitan regions concluded that there is little evidence
of a threshold of imperviousness below which there are no effects. Stream invertebrates showed
negative  impacts at the lowest levels of development, and the response appeared to be linear. In areas
without (or with little) prior agricultural  use, metrics of overall invertebrate health declined 25 to
33 percent relative to background  conditions  at just 10 percent impervious cover. At only 5 percent
impervious cover, the decline was  13 to 23  percent.232 Analysis of a  large biomonitoring data set from
Maryland showed declines of 110 out of 238 macroinvertebrate233 taxa at low levels of impervious
cover. Approximately 80 percent of the declining taxa began  declining at between 0.5 and 2 percent
impervious cover. The remaining 20 percent did so at levels between 2 and 25 percent.234 Finally, an
analysis of data from  357 fish collections in  the  Etowah River basin of Georgia between 1998 and 2003
found that some species become rare at impervious cover levels as  low as 2 percent.235

In 1994, researchers first proposed a model describing the relationship between the amount of
impervious cover in a watershed and stream health.236 A review of literature over a decade later found
that most research continued to support the model, but this  additional work suggested refinements.237
In the modified model, there are four stream  categories based on the degree  to which impervious cover
affects their quality (Exhibit 3-13).  The least affected category of stream, a sensitive stream, has an
229 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
230 King, etal. 2011
231 Sciera, et al. 2008
232 Cuffney, et al. 2010
233 A macroinvertebrate is an animal with no backbone that can be seen with the naked eye. Macroinvertebrates
include insects, spiders, worms, snails, slugs, and crayfish.
234 King, etal. 2011
235 Wenger, et al. 2008
236 Schueler 1994
237 Schueler, Fraley-McNeal, and Cappiella 2009

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
                 10%   20%         40%
                           Watershed Impervious Cover
  Exhibit 3-13: Impervious cover model. The white cone represents the observed
  variability in the response of streams to different levels of impervious cover. As the
  percentage of impervious cover in a watershed increases, stream quality declines. The
  dashed lines indicate that the transition point between stream classifications is variable.
  Image source: Schueler, Fraley-McNeal, and Cappiella 2009. Reprinted by permission of
  the publisher (American Society of Civil Engineers).
                                                                         impervious cover level of
                                                                         less than 5 to 10 percent.
                                                                         Stream quality with this
                                                                         level of impervious cover
                                                                         is generally fair to
                                                                         excellent, with quality
                                                                         influenced heavily by
                                                                         other characteristics of
                                                                         the watershed such as
                                                                         the amount of forest
                                                                         cover, agriculture, and
                                                                         road density. Stream
                                                                         quality shows the
                                                                         greatest variability at
                                                                         these lowest levels of
                                                                         impervious cover.
                                                                         Streams with impervious
                                                                         cover levels greater than
5 to 10 percent and less than 20 to 25 percent are impacted streams that show clear signs of declining
stream health. Streams with impervious cover greater than 20 to 25 percent and less than 60 to
70 percent are nonsupporting streams that are so degraded they no longer maintain their hydrology,
channel stability, habitat, water quality, and/or biological diversity. Finally, streams with impervious
cover greater than 60 to 70 percent are classified as urban drainage, with  quality that is consistently
poor. Urban streams might exist solely in storm drains at these levels of imperviousness.

3.3.6   Loss of Water Resources

As water resources are polluted and degraded, they can become unfit for drinking, swimming, fishing,
and other uses. However, water resources can also be strained if our use exceeds the available supply.
About 86 percent of U.S. households rely on public water supplies for their household use. About one-
third of the water from public water supplies comes from ground water, and two-thirds comes from
surface  water such as lakes and streams.238 For households that supply their own water, 98 percent rely
on ground water.239 Ground water use can exceed the rate at which precipitation  soaking into the
ground  can replenish it, leading to ground water depletion. Dry wells, reduced amounts of water in
streams and lakes, lower water quality, and land subsidence can result.240  Impervious surfaces created
by development241 and centralized wastewater treatment242 can decrease rates of ground water
   Kenny, et al. 2009
  ' Kenny, et al. 2009
  1 U.S. Geological Survey 2003
   Frazer 2005
  '' Vaccaro and Olsen 2007

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

recharge, exacerbating the effects of increased demand on ground water supplies. Ground water
depletion has been a concern in the Southwest and High Plains for many years, but increased demand
has stressed sources in many other areas of the country, including the Atlantic coastal plain, west-
central Florida, and the Gulf coastal plain, among others.243

3.4   Degradation of Air Quality

3.4.1  Criteria Air Pollutants

Land use, development, and transportation affect air quality in significant ways. For common air
pollutants, EPA has established and  regularly reviews National Ambient Air Quality Standards (NAAQS)
to protect public health and the environment. In setting or revising primary health-based standards, the
Agency considers the effects of poor air quality on at-risk populations such as children and the elderly.244
EPA has set standards for six principal pollutants (so-called "criteria pollutants"): carbon monoxide,
nitrogen dioxide, sulfur dioxide, lead, coarse particulate matter (PMi0), fine particulate matter (PM2.5),
and ozone.245 VOCs and NOX are precursors to the formation of ozone.246

With the exception of lead, which was phased out of gasoline from 1973 to 1996, motor vehicles
contribute to all of these forms of air pollution. Motor vehicles emit pollution through fuel combustion
(exhaust) during operation and fuel  evaporation during and between periods of operation. Gasoline-
powered vehicles are major contributors of pollution from VOCs, NOX, and  carbon monoxide. For diesel
vehicles, emissions of NOX and PM2.s raise the most serious health concerns.247  Fuel standards and
vehicle technology to reduce emissions from cars and other light-duty vehicles have dramatically
decreased the amount new cars pollute. Compared with a vehicle sold in 1970, one sold 40 years  later
emits 99 percent less carbon monoxide, NOX, particulate matter, and VOCs.248 Technology to reduce
diesel engine emissions was developed much later than technology to reduce gasoline engine emissions,
and heavy-duty vehicles tend to have a longer life span before being replaced with newer,  less polluting
vehicles.249 Reductions in diesel emissions have therefore been more modest, but declines will grow as
older vehicles are retired. EPA and the National Highway Traffic Safety Administration have set
increasingly stringent fuel economy standards through  model year 2025 to continue improvements in air
quality and reductions in greenhouse gas emissions (see Section 3.6).250
243 U.S. Geological Survey 2003
244 EPA, Our Nation's Air 2010
245 EPA, National Ambient Air Quality Standards 2012
246 Sawyer 2010
247 Sawyer 2010
248 Sawyer 2010
249 Sawyer 2010
250 National Highway Traffic Safety Administration, CAFE- Fuel Economy n.d.

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
Despite already impressive reductions in vehicle emissions since 1970, gains would be even greater if
not for the approximately 250 percent increase in VMT since then (see Section 2.5.1).251 More than
38 percent of national carbon monoxide emissions and 38 percent of nitrogen oxide emissions come
from highway vehicles (Exhibit 3-14). Stationary sources like power plants that provide energy to homes,
offices,  and industries are also major sources of pollution. Fuel combustion for residential, commercial,
and industrial uses is responsible for 83 percent of sulfur dioxide emissions and 32 percent of NOX
             Carbon monoxide      38.3%    17.8%     18.9% 13.6%

                      NOX     34.7%     21.5%    32.0%

                Sulfur dioxide  |           82.7%           14.3%

                     PM2.5    14.0%    17.0%      51.4%
                                             15.1%   25.5%
 Highway vehicles
I Off-highway mobile sources
I Fuel combustion
 Industrial and other processes
                          0%    20%   40%   60%   80%   100%
          Exhibit 3-14: National emissions by source sector, 2010. Miscellaneous sources include dust from
          construction and unpaved roads, agriculture, and others. Lead emissions data are from 2008 and
          combine highway vehicles and off-highway mobile sources into the single category "mobile
          Sources: EPA, Air Emission Sources 2008 and "1970-2012 average annual emissions" 2012
The amount people drive clearly has a significant bearing on air pollution levels. However, the amount of
infrastructure needed to accommodate cars contributes to air pollution regardless of the amount of
miles driven. A study that computed the lifecycle emissions of sulfur dioxide and PMi0 for cars showed
that adding parking lot construction and maintenance to the calculations raises emissions by as much as
24 percent and 89 percent, respectively, over calculations excluding these factors.253 Another study,
which reviewed 14 lifecycle assessments of road construction, concluded that the energy used in road
construction  equals the energy used by traffic on the road for one to two years.254 In addition, the
construction  of a lane mile of road produces the equivalent of the annual carbon dioxide emissions of 20
U.S. households.255
   Sawyer 2010
252 EPA, Our Nation's Air 2010
253 Chester, Horvath, and Madanat 2010
254 Muench 2010
   This calculation is based on the median value of carbon dioxide emissions for road construction projects
reviewed in the paper.

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

Despite progress in cleaning the air, as of 2012, approximately 159 million people—about half the U.S.
population—still lived in counties that failed to meet air quality standards, most frequently for ozone
and particulate matter.256 The Centers for Disease Control and Prevention evaluated the race and
ethnicity of the people living in counties failing to meet standards for PM2.5 and for ozone based on
2006-2008 and 2007-2009 data, respectively (Exhibit 3-15).257 Asians and Hispanics were most likely to
live in counties with poor air quality—more than 2.5 times as  likely as non-Hispanic whites to live in a
county failing to meet standards for PM2.s and more than 50 percent more likely than whites to live in a
county failing to meet standards for ozone. Another analysis of 2005-2007 national air quality
monitoring data that ranked all communities according to their air pollution levels found that the
proportion of non-Hispanic blacks in communities with the highest levels of PM2.5 and ozone is more
than twice the proportion in communities with the lowest levels.258
White, non-Hispanic
Black, non-Hispanic
American Indian/Alaska Native
Native Hawaiian/Other Pacific Islander
Non-Hispanic, multiple races
Percent of Population in Nonattainment
Counties for PM2.5 (2006-2008)
Percent of Population in Nonattainment
Counties for Ozone (2007-2009)
    Exhibit 3-15: Percentage of racial/ethnic groups living in nonattainment counties for PM2i5 and ozone in the
    United States. Nonattainment counties did not meet the National Ambient Air Quality Standards for the 2006 24-
    hour PM2.5 standard of 35 micrograms per cubic meter from 2006-2008 and the 2008 8-hour ozone standard of 75
    parts per billion from 2007-2009.
    Source: Yip, et al. 2011
3.4.2  Air Toxics

In addition to criteria air pollutants, EPA regulates hazardous air pollutants, also referred to as air toxics.
Air toxics are pollutants known or suspected to cause cancer or other serious human health effects or
ecosystem damage. Persistent air toxics are of particular concern in aquatic ecosystems, as toxic levels
can magnify up the food chain. Compared with the criteria pollutants, less information is available about
the health and environmental impacts of current levels of exposure to most individual air toxics.

Although natural sources such as volcanic eruptions and forest fires are responsible for some air toxics
releases, most air toxics are released by manmade sources such as cars, trucks, buses, and large,
stationary sources such as factories, refineries, and power plants. Some materials used in building
construction and some products such as cleaning materials can also cause indoor air exposures to air
  ' EPA, Summary Nonattainment Area Population Exposure Report 2012
  'Yip, etal. 2011
  'Miranda, etal. 2011
  ' EPA, About Air Toxics n.d.

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

EPA conducts a National-Scale Air Toxics Assessment every three years that estimates the risk of cancer
and other serious health effects from  inhaling air toxics. In 2011, EPA released its assessment based on
2005 data, the most recent year for which complete information was available.260 According to the 2005
assessment, mobile, on-road sources  like cars, trucks, and buses accounted for 39 percent of total
benzene emissions, 38 percent of total naphthalene emissions, 33 percent of total 1,3-butadiene
emissions, 21 percent of total formaldehyde emissions, and 8 percent of total acrolein emissions, among
other air toxics.261

In many places, exposure risk to air toxics varies by race and socioeconomic status. For example, one
study in Seattle and Portland, Oregon, compared the race and socioeconomic characteristics of all
people living in the cities' urban growth areas with the characteristics of the subset of those people
living near a road.262 Along high-volume roads in both cities, the concentration of African-Americans is
two to three times greater than the concentration of these groups in other areas of the city, and the
concentration of people living below the poverty level is 1.2 to 1.4 times greater.263

3.4.3  Human Health and Environmental Effects of Air Pollution

Air pollutants are associated with numerous public health problems and ecological effects. Exhibit 3-16
shows the wide range of effects of individual  air pollutants. Further, many of these pollutants can also
have synergistic effects, where their combined effect is greater than or different from the additive effect
of the individual pollutants, making reductions in the source of emissions potentially more important
than the reduction of individual pollutants through specific control technologies.264

Many of these health, environmental, and climate effects occur despite significant improvement in our
nation's air quality since 1990.26S For example, an  analysis of the health  effects of ground-level ozone
and PM2.5 based on modeled 2005 concentrations across the United States found that 130,000 to
340,000 premature deaths are attributable to these pollutants annually.266 The number of life years lost
due to ground-level ozone and PM2.5 varies by age. People over  age 65 lost an estimated 1.1 million life
years due to exposure to PM2.s and 36,000 life years due to ozone exposure, approximately 7 percent of
total life years lost among this cohort  in 2005. The effects of air  pollution vary among population
subgroups, including people of lower  socioeconomic status, people of color, the  young, and the elderly,
due in part to disproportionate exposure and a higher prevalence of underlying diseases that increase
susceptibility to air pollution.267'268
   EPA, 2005 National-Scale Air Toxics Assessment n.d.
261 EPA, "Air toxics pie charts" 2011
   The study considered people to be living near a road if they lived within 330 feet of a road having at least
100,000 vehicles per day, a zone in which people likely have higher risk of exposure to mobile-source air pollution.
263 Bae, et al. 2007
264 Giles, etal. 2011
265 EPA, Our Nation's Air 2012
266Fann, etal. 2012
267 Frumkin 2002

                                    Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
                              Human Health Effects
                                                                                Environmental and Climate Effects
                Decreases lung function and causes respiratory
                symptoms such as coughing and shortness of breath.
                Aggravates asthma and other lung diseases, leading to
                increased medication use, hospital admissions,
                emergency department visits, and premature mortality.
                                                      Damages vegetation by injuring leaves, reducing
                                                      photosynthesis, impairing reproduction and growth, and
                                                      decreasing crop yields.
                                                      Ozone damage to plants can alter ecosystem structure,
                                                      reduce biodiversity, and decrease plant uptake of CO2.
                                                      Contributes to the warming of the atmosphere.
Short-term exposures can aggravate heart or lung
diseases leading to symptoms, increased medication
use, hospital admissions, emergency department visits,
and premature mortality.
Long-term exposures can lead to the development of
heart or lung disease and premature mortality.
Impairs visibility, harms ecosystem processes, and damages
and/or soils structures and property.
Has variable climate impacts depending on particle type.
Most particles are reflective and lead to cooling, while some
(especially black carbon) absorb energy and lead to warming.
Changes the timing and location of traditional rainfall
                Damages the developing nervous system, resulting in IQ
                loss and impacts on learning, memory, and behavior in
                Causes cardiovascular and renal effects in adults and
                early effects related to anemia.
                                                      Harms plants and wildlife, accumulates in soils, and harms
                                                      both terrestrial and aquatic systems.
Aggravate asthma, leading to wheezing, chest tightness
and shortness of breath, increased medication use,
hospital admissions, and emergency department visits.
At very high levels can cause respiratory symptoms in
people without lung disease.
Contribute to the acidification of soil and surface water and
mercury methylation in wetland areas.
Injure vegetation and local species losses in aquatic and
terrestrial systems.
Contribute to particle formation with associated
environmental effects. Sulfate particles contribute to the
cooling of the atmosphere.
Aggravate lung diseases leading to respiratory
symptoms, hospital admissions, and emergency
department visits.
Increase susceptibility to respiratory infection.
Contribute to the acidification and nutrient enrichment
(eutrophication, nitrogen saturation) of soil and surface
Lead to biodiversity losses.
Affect levels of ozone, particles, and methane with
associated environmental and climate effects.
Reduces the amount of oxygen reaching the body's
organs and tissues.
Aggravates heart disease, resulting in chest pain and
other symptoms leading to hospital admissions and
emergency department visits.	
                                                                    •  Contributes to the formation of ozone.
                Some cause cancer and other serious health problems.
                Contribute to ozone formation with associated health
                                                    •  Contribute to ozone formation with associated
                                                      environmental and climate effects.
                                                    •  Contribute to the formation of CO2 and ozone, greenhouse
                                                      gases that warm the atmosphere.
Causes liver, kidney, and brain damage and neurological
and developmental damage.
Deposits into rivers, lakes, and oceans where it accumulates
in fish, resulting in exposure to humans and wildlife.
 Other air
Cause cancer; immune system damage; and
neurological, reproductive, developmental, respiratory,
and other health problems.
Some contribute to ozone and particle pollution with
associated health effects.
Harm wildlife and livestock.
Some accumulate in the food chain.
Some contribute to ozone and particle pollution with
associated environmental and climate effects.

 Exhibit 3-16: Health, environmental, and climate effects of air pollution.
 Source:  EPA, Our Nation's Air 2010
3.4.4    Indoor Sources of Pollution

Although outdoor air pollution receives widespread attention and is the subject of federal regulation,
people spend most of their time indoors, so exposure levels from indoor air pollution are of
considerable concern as well.  Many of the same pollutants in outdoor air are also inside, but people

268 Younger, etal. 2008

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

indoors can also be exposed to higher concentrations and/or additional indoor sources of pollution
including a wide array of chemicals from building materials, household products, and cleaning
supplies.269 People can also be exposed  to hazardous chemicals indoors through skin contact and
ingestion in addition to inhalation.270

The sources and effects of indoor pollutants include:

    •   Biological pollutants, including dust mites, fungi, bacteria, and pests (e.g., cockroaches and
       mice)—The primary health effects include  allergic reactions, from inflammation to asthma.
       Infections and toxic reactions can also occur.271
    •   VOCs, i.e., toxic gases that are emitted from certain substances at room temperature. VOCs
       include benzene, dichlorobenzene, ethylbenzene, chloroform, formaldehyde, methyl tertiary
       butyl ether, perchloroethylene, tetrachloroethene, toluene, and xylenes—They can  be found
       in personal care products, cleaning products, paints, pesticides, building materials, and
       furniture. The primary health effects vary depending on the compound. They include  eye and
       respiratory irritation, rashes, headaches, nausea, vomiting, shortness of breath, and cancer.272
    •   Asbestos, found mainly in older insulation, but also a wide variety of building materials and
       products including some vinyl floor tiles, shingles, and heat-resistant fabrics273—The primary
       health effects are lung cancer, mesothelioma, and (with occupational  exposures) asbestosis.274
    •   Incomplete combustion products of solid fuels, including carbon monoxide and particulate
       matter (e.g., from wood used for home heating)—The primary health effects of particulate
       matter include respiratory irritation, respiratory infections, bronchitis, and lung cancer.  Carbon
       monoxide exposure can cause low birth weight, headaches, nausea, and dizziness.
    •   Radon gas—The primary health effect is lung cancer.275 Radon is the second leading cause of
       lung cancer death, after smoking.276
    •   Polychlorinated biphenyls (PCBs), found in a wide variety of consumer products, including
       caulking in older buildings, paints, plastics, adhesives, and lubricants277—PCBs have  been
       shown to cause several adverse effects in animals, including cancer and immune, reproductive,
       nervous, and endocrine system  effects. Human studies provide evidence supporting these
    •   Polybrominated diphenyl ethers (PBDEs),  flame retardants found in a variety of consumer
       products including upholstery,  construction materials, and electrical appliances279— PDBEs are
269 Colbeck and Nasir 2010
270 Air Force Institute for Environment, Safety, and Occupational Health Risk Analysis n.d.
   Perez-Padilla, Schilmann, and Riojas-Rodriguez 2010
272 Perez-Padilla, Schilmann, and Riojas-Rodriguez 2010
   EPA, Learn About Asbestos n.d.
274 Perez-Padilla, Schilmann, and Riojas-Rodriguez 2010
   Perez-Padilla, Schilmann, and Riojas-Rodriguez 2010
276 Al-Zoughool and Krewski 2009
277 Rudel and Perovich 2009
278 EPA, Health Effects of PCBs n.d.
279 Rudel and Perovich 2009

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
        not chemically bound and can degrade into particles found in air and house dust.280'281 Animal
        research suggests PBDEs can cause neurodevelopmental, kidney, thyroid, and liver toxicity and
        can disrupt endocrine systems.282

The federal government has not established standards for safe levels of most indoor air pollutants.283
Far less information is available about population exposure levels and health effects from indoor air
pollution than for outdoor air pollution. Study design and interpretation are complicated by the
difficulty of assessing exposures and effects of chemical and biological mixtures and by variation across
buildings resulting from outdoor pollutant concentrations, building ventilation, building materials,
relative humidity, temperature, and activities of the building occupants.284 In addition, the relative
scarcity of research for any specific  pollutant is due in part to the sheer number of chemicals and
potential health effects that require further analysis.285

A literature review found that indoor air
pollutant exposures have changed a great
deal  since the 1950s.286 Exposure  to known
and suspected carcinogens (e.g., benzene,
formaldehyde, asbestos, chloroform, and
trichloroethylene) has decreased, as has
exposure to recognized toxics such  as
carbon monoxide, sulfur dioxide,  nitrogen
dioxides, lead, and mercury. However,
indoor levels of endocrine disrupters,
chemicals that mimic or block natural
hormones, have increased. Known or
suspected endocrine disrupters include
phthalates found in certain flexible  plastics,
some flame-retardant chemicals,
bisphenol-A,  and nonylphenol.
The public health literature on air pollution
focuses predominantly on children, who
suffer disproportionately from air pollution
because their respiratory systems are still
Exhibit 3-17: Baby exploring at home. Children might be more
vulnerable to exposure to indoor contaminants because their lungs
and metabolic systems are still developing and they breathe and
eat more per pound of body weight than adults. Children also play
close to the ground where they might consume contaminated dust
and tracked-in pollutants, and they might put toys and household
objects in their mouths.
Photo source: Ramona Gaukel via stock.xchng
   Johnson, et al. 2010
  1 Dodson, etal. 2012
  1 EPA, Technical Fact Sheet 2012
  ' Bernstein, et al. 2008
  'Colbeck and Nasir 2010
  5 Weschler 2011
  ' Weschler 2009

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

developing.287 A review of research published between 1996 and 2007 that considered the effect of
indoor air pollution on the respiratory health of children under the age of five found only a few studies
with widely varying methodologies, which limits broad conclusions.288 However, the results suggest that
several indoor air pollutants, including nitrogen dioxide and VOCs, are associated with adverse
respiratory effects in young children at levels commonly encountered in developed countries. A review
of 21 epidemiologic studies on the association between indoor chemical exposures and respiratory
health in infants and children found a relatively consistent association between elevated risk of
respiratory or allergic effects and exposure to formaldehyde-emitting materials (e.g., paints, adhesives,
insulation, and cabinetry), flexible plastics, and recently painted surfaces.289 Excess indoor moisture is
also associated with adverse health effects. A review of epidemiologic studies found associations
between indoor dampness or mold and  a range of respiratory and allergic health effects, including
asthma, bronchitis, shortness of breath, coughing, respiratory infections, and other upper respiratory
tract symptoms.

Similar to the exposure to outdoor air pollution discussed in Sections 3.4.1 and 3.4.2, racial disparities
exist in exposure to  indoor pollution, although less research has focused on this issue. The
socioeconomic status of a household tends to  influence several factors that can affect indoor pollution
levels, including the size and design of housing, the amount of leakage or air exchange with the
outdoors, cooking practices, and the selection  of consumer products.291 Analysis of exposure to  10 VOCs
for a sample of the U.S. population aged 20 to  59 found that Mexican-Americans had greater exposure
to benzene and 1,4-dichlorobenzene than non-Hispanic whites and  blacks. Non-Hispanic blacks had
higher exposures than both other groups to chloroform and than Mexican-Americans to
tetrachloroethene. The differences were due mainly to associations between race and home location
(which determines whether household water is chlorinated), use of air fresheners, and use of dry
cleaners.292 A different analysis of the same dataset showed that race or ethnicity was the strongest
determinant of exposure levels among all factors studied. Hispanics and blacks had the highest
exposures to  benzene, toluene, ethylbenzene, xylenes, methyl tertiary butyl ether (a gasoline additive),
and dichlorobenzene. In addition to race, other important risk factors for exposure to one or more of
the studied toxics were: living in a home with an attached garage; keeping windows closed year round;
smoking; using dry cleaning, stain removers, chlorinated water, moth repellents, and air fresheners; and
being exposed to gasoline, fuels,  paints, and glues.293 A study of households in Los Angeles, Houston,
and Elizabeth, New Jersey, considered the cancer risks of Hispanics and non-Hispanic whites due to 12
air toxics. For both Hispanics and whites, the cancer risk for nine of the 12 pollutants was greater than
the EPA benchmark of 10"6.  In both Houston and Elizabeth, Hispanics had a higher combined cancer risk
   Fuentes-Leonarte, Tenias, and Ballester 2009
288 Fuentes-Leonarte, Tenias, and Ballester 2009
289 Mendell 2007
290 Mendell, et al. 2011
291 Adamkiewicz, et al. 2011
292 Wang, etal. 2009
293 D'Souza, et al. 2009

                           Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

than whites, mainly due to exposure to p-dichlorobenzene, a component of some deodorizers, air
fresheners, and moth repellents that does not have a significant outdoor source.294

3.5   Heat Island Effect

Not only do impervious surfaces create water quality problems, they also affect the temperature of
surrounding areas through what is known as the heat island effect. Cities can be as much as 6 to 8
degrees Fahrenheit warmer than outlying areas.295 The heat island effect is due to two complementary
forces: dark pavement and roofs absorb and reflect more of the sun's heat, while the relative scarcity of
trees and other vegetation reduces shade and cooling through evapotranspiration.

Increased heat is itself a health hazard, as heat stroke can lead to hospitalization and even death. A
review of studies found that while methodological differences hamper efforts to summarize effects, two
recent estimates of the effect of temperature on mortality in the United States using identical methods
found consistent results for different regions of the country. Both  studies found that a 10°F increase in
apparent temperature is associated with an approximately 2 percent increase in mortality.296 However,
a study of 107 U.S. communities suggests that the exact relationship will vary by location depending on
community characteristics including income, unemployment,  population, and the  percentage of the
population that is urban versus rural.297 The effects of heat tend disproportionately to affect poor and
elderly people.298

Increased heat can also lead to other health effects. As temperatures rise, more VOCs are emitted from
vehicles, and natural forms of VOCs that are emitted by some tree species increase.299 Heat also directly
increases the rate of ozone formation.300 In addition, as temperatures rise, people use more air
conditioning, which increases air pollution as regional power plants ramp up production and emit more
particulate matter, SOX,  NOX, and air toxics.301

3.6   Greenhouse Gas Emissions and Global Climate Change

Greenhouse gases trap heat in the atmosphere  and increase the earth's temperature. Several naturally
occurring greenhouse gases keep the earth warm enough to support human life. However, human
activity is also responsible for a large increase in the amount of greenhouse gases  we have in the
atmosphere. Carbon dioxide, methane, nitrous oxide, and fluorinated gases are the four main
294 Hun, etal. 2009
295 Frumkin 2002
296 Basu 2009
297 Anderson and Belle 2009
298 Frumkin 2002
299 Stone 2008
300 Frumkin 2002
301 Frumkin 2002

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

greenhouse gases emitted from human sources.302 These greenhouse gas emissions contribute to global
climate change, which causes a range of detrimental human health and environmental effects.

3.6.1  Greenhouse Gas Emissions Sources

In 2010, U.S. greenhouse gas emissions totaled 6,821.8 teragrams (or million metric tons) of carbon
dioxide (CO2) equivalent (Tg  CO2 Eq.), an increase of 10.5 percent since 1990.303 Emissions fluctuate
annually due  in part to economic conditions, energy prices, and weather. Longer-term changes are due
to the size of the population, energy efficiency, and several factors directly related to our built
environment, including development patterns and market trends that influence the amount people
drive and the size of homes.304 About 16 percent of total U.S. greenhouse gas emissions in 2010 were
offset by the  uptake of carbon dioxide in the atmosphere by U.S. sinks, primarily from forests
(86 percent) but also from urban trees (9 percent), the management of agricultural soils (4 percent), and
landfilled yard trimmings and food scraps (1 percent).305

Electricity generation was the largest source  of U.S. emissions in 2010, accounting for 34 percent of the
total.306 When emissions from  electricity are  attributed to an economic sector, industrial activity
accounts for the largest  portion of total U.S. greenhouse gas emissions, followed closely by
transportation (Exhibit 3-18). The residential and commercial sectors together account for just over a
third of total  U.S. greenhouse gas emissions, with the remainder attributed to agriculture and the U.S.
                             Agriculture, 7.6%
U.S. Territories,
                                      17.2%    Transportation,
          Exhibit 3-18: U.S. greenhouse gas emissions by economic sector including emissions from
          electricity distributed among sectors, 2010.
          Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
   EPA, Greenhouse Gas Emissions n.d.
  ' EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  1 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  1 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  1 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
territories.   Greenhouse gases from the transportation sector are due to passenger cars (43 percent);
freight trucks (22 percent); light-duty trucks, which include sport utility vehicles, pickup trucks, and
minivans (19 percent); and commercial aircraft (6 percent).308

Transportation emissions increased 19 percent between 1990 and 2010, primarily from carbon dioxide
emissions from fossil fuel combustion, but also in part from an increase in hydrofluorocarbons from
vehicle air conditioners and refrigerated trucks (Exhibit 3-19).309 The emissions increase was due
primarily to the increase in VMT over this period (see Section 2.5.1), which was partially offset by a slight
increase in average fuel economy as older vehicles were removed from the roads.310 Among new
vehicles sold, average fuel economy actually declined between 1990 and  2004 as sales of sport utility
vehicles and other light-duty trucks increased. In the 1970s, about one-fifth of new vehicles sold were
light-duty trucks. By 2004, they had increased to more than half of the market, although this trend  has
since begun to reverse.311 A 4 percent decline in transportation emissions between 2008 and 2009  is due
in part to decreased economic activity, particularly the demand for freight transport. As economic
activity began to rebound in 2010, transportation emissions increased by 1 percent.312
                                                                        • Industry
                                                                        • Residential
          Exhibit 3-19: U.S. greenhouse gas emissions with electricity distributed to economic sectors,
          Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
Emissions from the residential and commercial sectors also increased relatively steadily between 1990
and 2010: by 25 percent in the commercial sector313 and 29 percent in the residential sector (see Exhibit
3-19). Both sectors' emissions are due primarily to electricity use, followed by petroleum and natural gas
   EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  5 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
   EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  5 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  L EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  " EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
  ' The commercial sector includes landfills and wastewater treatment in these data.

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

use. Short-term trends in emissions in these sectors are often due to weather conditions that increase
the need for heating and/or cooling. In the long term, the emissions trends in these sectors are affected
by population growth, population distribution across the country, and changes in the size and energy
efficiency of buildings.314

3.6.2  Effects of Global Climate Change

How much energy our buildings consume and how much people drive both affect greenhouse gas
emissions, making the built environment an important contributor to global climate change. A 2011
report by the National Research Council of the National Academies concluded that global climate change
is occurring and is largely due to human activities that lead to heat-trapping greenhouse gas
emissions.315 The scientific academies of over 30 countries316 and the Intergovernmental Panel on
Climate Change, an intergovernmental scientific body, reached the same conclusion based on
contributions from thousands of scientists and an  extensive  review process.317

Because climate changes caused by carbon dioxide persist for a very long time, warming will continue
well past the end of this century.318 The 2009 National Climate Assessment found that already-observed
changes in the United States include:

   •   Temperature—From 1958 to 2008, the average temperature rose more than 2 degrees
       Fahrenheit, and precipitation increased by an average of about 5 percent.
   •   Rainfall—Over the past century, the amount of rain  falling in the heaviest 1 percent of
       downpours has increased by an average of about  20 percent, ranging regionally from a
       9 percent increase in the Southwest to a 67 percent  increase in the Northeast.
   •   Extreme weather—Extreme weather events have become more frequent and intense. Atlantic
       hurricanes have become stronger and more frequent since the 1980s, although the number of
       hurricanes making landfall on U.S. soil has not changed substantially. In the Pacific, while storms
       became stronger over the same time period, they have not become more frequent. Droughts
       have become more frequent in the West and the Southeast since the 1960s. Heat waves with
       dangerously high nighttime temperatures have increased over the past 30 to 40 years.
   •   Winter storms—Over the last 50 years, winter storms have shifted northward and are becoming
   •   Wildfires—In the western United States in particular, wildfires have become more frequent and
       lasted longer, and wildfire seasons are longer.
   •   Sea level—Sea level along some sections of the U.S.  coast rose by as much as 8 inches from
       1958 to 2008.
   EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 2012
315 National Research Council of the National Academies 2011
316 Transportation Research Board of the National Academies 2012
   Intergovernmental Panel on Climate Change 2007
318 National Research Council of the National Academies 2011

                          Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
                                       Exhibit 3-20: Flooding of the Monocacy River in Montgomery County,
                                       Maryland. Climate change is likely to increase the number and severity
                                       of floods in many areas of the country, placing human life at risk while
                                       harming ecosystems, dispersing pollutants, and destroying property.
                                       Photo source: EPA
    •  Sea ice—Arctic sea ice has
       shrunk by 3 to 4 percent per
       decade since 1979.319

These impacts are projected to
continue to increase over the next
century. The length of time over which
changes will continue and the severity
of the changes depend on the level of
greenhouse gas emissions and the
climate's sensitivity to those emissions,
as well as other factors such  as abrupt
changes to the climate.320

Our built environment affects climate
change, but it  is also affected by
climate change. Changes to the water
cycle mean that both floods and
droughts are more common, putting  lives and property at risk, stressing water infrastructure, and
changing the amount and quality of water available for human use. Warmer weather increases energy
use for cooling and decreases it for heating, changing the levels and periods of peak demand. Floods,
extreme heat, and  sea level rise put transportation infrastructure such as roads and rail lines at risk and
increase the chances of travel and freight delays and disruptions.321

Climate-related changes to the natural environment include major shifts in  species' ranges, which can
increase the risk  of extinction,  and migration patterns. Plant growing seasons are changing as well, and
pollen seasons for some plants are longer, which affects people allergic to pollen. Changing climate
conditions make it  easier for some invasive species to take hold (see Section 3.1.2). Plants stressed by
drought or heat are more vulnerable  to insect pests. Warmer temperatures increase the range of some
diseases that affect wildlife. The drier, hotter climate raises the risk of wildfires, which burn habitat.322

With the increase in heat waves and extreme heat, the likelihood of illness and death from heat waves
also rises (see  Section 3.5). Elderly and already-ill people are more vulnerable to adverse health effects
from extreme  heat, so the growing elderly population and the rising rates of chronic illnesses such as
diabetes mean that, without adaptation strategies that help reduce the risk, more people are likely to
die from extreme heat. While milder  winters could reduce deaths from extreme cold, the number of
heat-related deaths is likely to outstrip that reduction, resulting in a net increase in death rates.323
' U.S. Global Change Research Program 2009
1 U.S. Global Change Research Program 2009
 U.S. Global Change Research Program 2009
 U.S. Global Change Research Program 2009
 U.S. Global Change Research Program 2009

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

The higher temperatures and increased water vapor attributable to global climate change are projected
to increase ozone pollution in already-polluted areas (see Section 3.4.1). By 2050, if current pollution
levels remain constant, days on which ozone concentrations are considered unhealthy for everyone are
projected to increase by 68 percent—due solely to warming temperatures—in the 50 largest cities in the
eastern part of the country.324

The increase in extreme events also increases the risk to human life and well-being. Floods can increase
sewer overflows, which can contaminate drinking water.  Hurricanes and other strong storms can
directly threaten human life and can also cause mental health effects such  as post-traumatic stress
disorder and depression. Wildfires can cause respiratory illnesses in addition to direct harm from

3.7    Other Health and Safety Effects

The built environment's effects on human  health extend beyond exposure  to air and  water pollution or
global climate change as already discussed. How we build our communities affects health and safety in
several ways. The built environment affects levels of physical activity, obesity, and chronic  disease. It
also influences our emotional health and the degree of engagement in our  communities. Finally, how we
design our streets and towns affects the likelihood of  being hurt or killed in a vehicle  crash.

3.7.1  Activity Levels, Obesity, and Chronic Disease

How we build our cities, towns, and suburbs affects the amount of time people spend in their cars and
the opportunity, practicality, and necessity of physical activity in the course of meeting daily needs.
These factors can influence overall physical activity levels and therefore the risk of obesity  and chronic
disease, including heart disease, hypertension, stroke, high cholesterol, osteoarthritis, gall  bladder
disease, type 2 diabetes, and some cancers.326'327These public health threats are of increasing concern
as the number of overweight and obese Americans grows. For adults aged  20 to 74, the prevalence of
obesity more than doubled between the late 1970s and 2007-2008.32S As of 2008, 68 percent of adults329
and 18 percent of children ages 2-9330 were overweight or obese.

A considerable body of work exists on the association  between the built environment and obesity. Broad
conclusions are hard to reach due to differences across studies in the features of the  built environment
that were  studied. Nevertheless, a 2010 literature review of 63 papers concluded that the degree of land
use mix and county-level measures of sprawl are among the most common metrics used and therefore
324 U.S. Global Change Research Program 2009
325 U.S. Global Change Research Program 2009
326 Frank, et al. 2006
327 Frumkin 2002
328 Ogden and Carroll 2010
329Flegal, etal. 2010
330 Ogden and Carroll 2010

                             Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

allow the most robust conclusions, namely that both likely affect the incidence of obesity.331 For
example, one study found that a 10 percent increase in how evenly square footage is distributed across
land use types (residential, public, and commercial) was associated with a nearly sixfold increase in
walking for transportation and a 25 percent reduction  in the prevalence of overweight and obese adults,
while controlling for sociodemographic factors.332 Another comprehensive review in  2012 also noted the
challenges of summarizing the literature on the built environment and physical activity given
methodological shortcomings and differences across studies.333 The main finding of this review was that
while data are lacking to resolve whether the built environment determines levels of physical activity
and/or obesity, nearly 90 percent of studies found a positive association, suggesting that the built
environment is one of the many factors that could play a role in how much people exercise and levels of

Some subpopulations are more affected by obesity and related chronic disease than  others.334 Mexican-
American women and children; Native Americans; Pacific Islanders; and poor black men, white women,
and children have disproportionate levels of obesity at all ages.335 A possible contributing explanatory
factor is that these groups tend to have fewer and poorer-quality recreational facilities in their
neighborhoods. A national analysis showed that as the number of minorities and people of lower
socioeconomic status increases in an
area, the number of physical activity and
recreational facilities often decreases.336
Similarly, an analysis of the Los Angeles
metropolitan area shows that  Latinos,
African-Americans, and low-income
groups are more likely to live in
neighborhoods with smaller parks and
higher population density.337 In addition,
the public park spaces that exist tend to
receive less maintenance and are often
perceived as unsafe. A study of 685
neighborhoods in North Carolina, New
York, and Maryland looked at the
availability of public recreational
facilities and parks and residents' race
Exhibit 3-21: Meridian Hill Park in Washington, D.C. Parks and
other recreational facilities can provide opportunities for physical
activity close to home.
Photo source: EPA
   Feng, et al. 2010
332 Li, et al. 2008
333 Ferdinand, etal. 2012
334 Ferdinand, etal. 2012
335 Wang and Beydoun 2007
336 Gordon-Larson, et al. 2006. Recreational and physical activity facilities included schools, recreation centers,
youth centers, parks, golf courses, instructional studios, sporting and recreational camps, swimming pools, and
athletic clubs, among others.
337 Sister, Wolch, and Wilson 2010

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

and socioeconomic status. Hispanic/black and Hispanic neighborhoods were seven and nine times,
respectively, less likely than white neighborhoods to have a facility. Black and racially mixed areas were
two and three times, respectively, less likely than white neighborhoods to have a facility in the area.
Parks in these neighborhoods were generally much more equitably distributed than other types of
recreational facilities, although their size and quality were not assessed.338

Overall, available research suggests that among recreational facilities and resources, public parks tend
to be the most equitably distributed.339 For example, researchers investigated how local park access,
walkable neighborhoods, and both together are related to the percentage of the population consisting
of Latinos, African-Americans, and children in Phoenix, Arizona. Walkability was  measured based on
housing density, connectivity, and land use diversity. The most walkable census block groups with the
best park access had fewer children, but counter to predictions, they also had more Latinos and African-
Americans.340 However, these areas also had higher crime rates, and parks tended to be smaller.
Concern for personal safety and limited options within parks might therefore reduce physical activity in
these neighborhoods regardless of available facilities.

In spite of the findings that subpopulations have different levels of opportunity for physical activity in
their neighborhoods, relatively little research has focused on the association between the built
environment and actual physical activity levels for different subgroups, particularly poor and minority
communities.341 However, a 2002 national survey of 3,600 households with children aged 9 through 13
suggests that the built environment does likely play a role in the availability of opportunities for and
participation in  physical activity. The survey found that while 13 percent of white parents reported that
lack of opportunities in the area was a barrier to their child's participation in physical activities, more
than 30 percent of black and Hispanic parents reported the same obstacle.342

3.7.2  Emotional Health and Community Engagement

A built environment with homes separated from businesses and jobs leaves people few options but to
spend large amounts of time in their cars to get to work and meet their daily needs. Some people like to
commute because they value the time spent commuting as a transition between work and home life.343
However, many people spend more time commuting than they would like,344 which limits the amount of
time and energy they can devote to other activities. A built environment that requires or encourages
people to spend a significant amount of time in their cars reduces opportunities for informal,
spontaneous social interactions with neighbors and acquaintances, shifts activities away from public
338 Moore, et al. 2008
339 Moore, et al. 2008
340 Cutts, et al. 2009
341 Ferdinand, etal. 2012
342 Duke, Huhman, and Heitzler 2003
343 Dry, et al. 2004
344 Redmond and Mokhtarian 2001

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

spaces such as playgrounds, and can disrupt community life as people age and must move to find
different housing options to suit their needs and incomes at different life stages.345

Such observations relate to the concept of social capital, the benefit that people get emotionally and
physically from interpersonal relationships and the broader benefit to communities when its members
participate in political organizations, charitable activities, community organizations, and group
recreational activities.346 A review of the literature shows that neighborhoods with more walkable
streets, more public space, and a diverse mix of land uses are associated with improved social capital.
Automobile dependence, lack of public spaces, and  low density tend to be associated with reduced
social capital.347 A study of three New Hampshire communities had similar results. This study looked at
the effect walkability had on residents' levels of social capital.348 The communities differed in the
number of destinations residents reported being able to walk to, such as a friend's house, the post
office, or stores.  Residents of the more walkable communities reported higher levels of all measures of
social capital, including trusting neighbors "a lot," participating in community projects, visits from
friends at home, volunteer activities, and attendance at club meetings.

3.7.3  Vehicle Crashes

How much people drive and their travel speed are the most important factors that determine their
exposure to the risk of injury or death from vehicle crashes, as well as the risk to others. Although
absolute risk estimates vary widely, all studies that have examined the relationship between speed and
fatality risk report that risk increases with vehicle speed.349 Development patterns and the design of our
communities influence  both how much and how fast people drive.350 The width of travel lanes and
shoulders, measures to slow traffic, and even the presence of street trees influence the risk of injury or
death from vehicle crashes.

In 2010, 32,885 people  died in the United States in vehicle crashes, including vehicle occupants and
pedestrians,351 down from 50,894 in 1966.352 Many different factors are undoubtedly responsible for the
decline, from safer cars and seatbelt laws to tougher laws against drunk driving.353 The safety gains over
this period would have  been greater but forthe increase in VMT. While the number of fatalities per
number of people declined nearly 60 percent over this period, from 2.6 to 1.1 per 10,000 residents,
vehicle fatalities  per 100 million VMT declined 80 percent, from 5.5 to 1.1 (Exhibit 3-22).
345 Frumkin 2006
346 Jackson 2003
347 Frumkin 2006
348 Rogers, et al. 2011
   Rosen, Stigson, and Sander 2011
350 Ewing and Dumbaugh 2009
351 National Highway Traffic Safety Administration, PARS Data Tables n.d.
   National Highway Traffic Safety Administration 2001
353 Frumkin 2006

Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel
                                                                    • Fatalities per 100 million
                                                                    • Fatalities per 10,000
               1966 1971 1976 1981 1986 1991  1996  2001  2006
            Exhibit 3-22: Fatalities per VMT and per population, 1966-2010.
            Sources: National Highway Traffic Safety Administration, PARS Data Tables n.d., 2001 (Table 2),
            and 2012 (Table 2); U.S. Department of Transportation 2012, Table 2-17
In spite of an overall downward trend in traffic fatalities, they are nevertheless a leading cause of death
for many cohorts. In 2007, motor vehicle crashes were the leading cause of death for people aged 3
through 33, excluding children aged 6, 7, and 10.354 Car crashes are the third leading cause of death in
terms of years of life lost given the young age of so many car crash victims and the number of years they
would  have been expected to live if they had not died in a car crash. Only cancer and heart disease are
responsible for more years of life lost.355 High as it is, the number of traffic fatalities pales in comparison
to the number of people injured. In 2010, 3,341,640 people (377,798 of them  pedestrians or cyclists)
suffered non-fatal traffic-related injuries,356 almost 100 times the number that died.357

Several studies have investigated the relationship between vehicle crashes and the form of our built
environment. A review of the literature shows that as population density increases, so do crash rates per
VMT. However, increased population density is also associated with reductions in per capita VMT
(reducing per capita crash rates) and reductions in travel speed (which is the primary determinant of
crash severity).358 One study considered the association between crash fatalities and a sprawl index359
across  448 counties in the 101 largest metropolitan areas.360 Places with high-density residential
   Subramanian 2011
  ' Subramanian 2011
  ' Centers for Disease Control National Center for Injury Prevention and Control, WISQARS Nonfatal Injury Reports
   Centers for Disease Control National Center for Injury Prevention and Control, WISQARS Fatal Injury Reports
   Ewing and Dumbaugh 2009
359 Many studies reported in this document use one of several composite sprawl indices. They incorporate multiple
aspects of urban form such as density, land use mix, connectivity, and centeredness, in an attempt to develop a
concise quantitative description of how sprawling or compact an area is.
360 Ewing, Schieber, and Zegeer 2003

                            Environmental Consequences of Trends in Land Use, Buildings, and Vehicle Travel

development; homes, shops, and workplaces in the same area; a distinct downtown or activity center;
small blocks; and well-connected streets scored highest on the index. The study found that it is safer to
be in places with these characteristics. Every 1  percent increase in the index was associated with a
1.5 percent decrease in traffic fatalities. The decrease was greater, 1.5 to 3.6 percent, if only those
fatalities involving pedestrians were included, after adjusting for the amount of time people walk in
different locations.

Poor and minority populations suffer a disproportionate number of pedestrian fatalities. The causes of
the disparity are complex, possibly involving differences in the amount of walking based on access to
personal vehicles and use of public transportation, street design in areas where poor and minority
individuals live,  and cultural factors such as experience with traffic.361

3.8     Summary

As the U.S. population has grown, we have developed land that serves important ecological functions at
a significant cost to the environment. Development has destroyed, degraded, and fragmented habitat.
Water quality has declined. Air quality in many areas of the country is still adversely affecting human
health. The heat island effect and global climate change illustrate just how complex and far-reaching the
impacts of our built environment are. Community design can make it difficult for people to get adequate
physical activity, engage with neighbors, and participate in community events. It can  also increase the
risk of injury or death from a vehicle crash.

The next chapter discusses the impacts of different development patterns to help communities
understand how their choices about where and how to develop can better protect the environment and
residents'  health and safety.
361 Frumkin 2006

Chapter 4. Effects of Different Types of Development on the
In over 40 years since the creation of EPA, the country has made significant advancements in cleaning
our air and water and protecting critical lands and habitat. However, environmental problems remain,
and the built environment affects our ability to address these problems. Where and how we build affect
attainment of national environmental goals in each of the following areas:

    •   Taking action on climate change and improving air quality—Our ability to reduce air pollution
       emissions and greenhouse gases depends in part on how much people drive and the energy
       efficiency of our buildings.
    •   Protecting America's waters—Our ability to protect water quality depends in part on the
       amount of impervious surface we create in our developed areas and how effectively we can
       preserve  undeveloped land.
    •   Cleaning  up communities and advancing sustainable development—Our ability to create
       healthy and safe communities depends in part on whether we are able to clean up and
       repurpose developed areas that have been neglected.
    •   Ensuring  the safety of chemicals and preventing pollution—Our ability to prevent toxic
       chemicals from entering the environment depends in part on the materials we use to build our
       homes and businesses.
    •   Enforcing environmental laws—Environmental laws help us achieve all of the above,
       particularly by ensuring the protection of low-income, minority, and tribal communities that are
       disproportionately affected by pollution.362

EPA's environmental goals and national efforts have historically focused on reducing tailpipe and
smokestack emissions. As Congress passed legislation to address environmental and human health
threats, EPA responded with regulations aimed  largely at controlling the most obvious risks, such as
pollution  from large industries. It has become increasingly clear that this approach alone is not
sufficient. EPA now recognizes that "development and building construction practices may result in a
broad range of impacts on human health and the environment" and promotes sustainable communities
that "balance their economic and natural assets so that the diverse needs of local residents can be met
now and  in the future with limited environmental impacts."363

As communities consider how to grow, they are looking for strategies that will protect the environment
while encouraging new economic opportunities and improving quality of life. Different development
patterns can affect the environment in different ways. The direct effects of habitat consumption  and
disruption are well documented and widely accepted. By contrast, the effects of different development
patterns on travel and emissions are somewhat less understood, and the exact magnitude of these
   EPA, FY 2011-2015 EPA Strategic Plan 2010
  ; EPA, FY 2011-2015 EPA Strategic Plan 2010, pp. 15-16

                                            Effects of Different Types of Development on the Environment
effects is still subject to some debate. This section synthesizes research findings, noting where greater or
less certainty exists about linkages between causes and effects and the relative magnitude of effects.
Where previous sections described broad land use and transportation trends and impacts, this section
focuses on impacts of conventional development versus more environmentally sensitive development.

Certain characteristics of the built environment are associated with beneficial environmental  results.
They can be divided broadly into two categories:

    •   Where we build involves locating development in a region or land area. It includes safeguarding
       sensitive areas such as riparian buffers, wetlands, and critical habitat from development
       pressures; directing new development to infill, brownfield, and greyfield sites364 to take
       advantage of existing infrastructure and preserve green space; and putting homes, workplaces,
       and  services close to each other in convenient, accessible locations.
    •   How we build includes developing more compactly to preserve open spaces and water quality;
       mixing uses to reduce travel distances; designing communities and streets to promote walking
       and  biking; and improving building design, construction, and materials selection to use natural
       resources more efficiently and improve buildings' environmental performance.

These elements are interrelated and often work most effectively in  combination with each other rather
than individually. For example, encouraging compactness through infill or brownfields redevelopment
often facilitates mixed-use development  and creates the type of environment that makes transit use,
walking, and bicycling easier and more appealing. Developing more compact development can help
safeguard environmentally sensitive areas.

Incorporating one beneficial  element without others could have minimal effects or possibly prove
detrimental  to environmental goals. For example, increasing density without protecting environmentally
sensitive areas or improving transit access could result in increased water quality  impacts, traffic
congestion,  or air quality problems. Likewise, locating energy-efficient  homes far from an employment
center and other amenities can increase total energy expenditures as residents drive longer distances to
work and other activities.

Because most practices work synergistically with one another, isolating the effects of one from another
can be difficult. In general, the studies presented in this chapter were chosen because they attempt to
isolate the effects of individual strategies. However, studying one technique in isolation is often  nearly
impossible, and the value of doing so is somewhat limited, as most practices are used in combination
with others. Nonetheless, although findings might differ on the magnitude of the  effects of different
practices, the evidence is overwhelming that some types of development yield better environmental
results than  others. Researchers have estimated that as much as two-thirds of the development that will
364 Greyfields are formerly economically viable sites that suffer from disinvestment, often retail shopping malls,
strip centers, or office parks. By definition, greyfields have no environmental contamination (or they would be
considered brownfields), and they can offer important attributes for developers such as a large lot size, existing
infrastructure, and an accessible location.

Effects of Different Types of Development on the Environment
exist in 40 to 45 years does not exist today,365 meaning that decisions we make about how and where
that development occurs could significantly affect our health and the health of the environment.

4.1   Where We Build

Where we locate development has significant impacts on environmental resources. Development in and
adjacent to already-developed areas can help protect natural resources like wetlands, streams,
coastlines, and critical habitat. Protecting natural lands from development can reduce impacts on
habitat and water resources, reduce VMT and associated air pollutants, foster social connections, and
improve human health.

This section covers the following aspects of where we build:

    •   Safeguarding sensitive areas.
    •   Infill development in built-up areas.
    •   Focusing development around existing transit stations.

4.1.1  Importance of Safeguarding Sensitive Areas

Using land for development more efficiently makes it easier to conserve natural lands. Communities can
encourage development in places where transportation, utilities, and public services such as schools and
hospitals already exist; in areas adjacent to built-out communities; and on brownfields and greyfields.
Encouraging development in these places, where infrastructure already exists and the environment has
already been disturbed, can reduce pressure to develop farmland and sensitive natural areas such as
wetlands, flood plains, mature forests, drinking water source areas, and shorelines. These areas serve
important ecological functions (see Section 3.1), and their preservation provides valuable scenic and
recreation areas.

In addition, development in sensitive areas like coastal zones can exacerbate the ecological effects of
sea level rise and other impacts of global warming.366 Climate change and habitat destruction from
development and shoreline stabilization are some of the most serious threats to coastal species and
ecosystems.367 Protecting coastal areas from development can also help keep people away from areas
prone to natural hazards and limit the demand for shoreline stabilization.368 As global warming
increases, hurricanes, flooding, and wildfires are likely to increase,369 so avoiding development in areas
most vulnerable to these natural disasters such as coastal  areas, flood plains, and wildfire-prone forests
will help keep property and people out of harm's way. Communities will also need to consider that areas
   Ewing, Bartholomew, et al. 2008
366 Defeo, et al. 2009
367 Grain, et al. 2009. Other threats that consistently rank highly are invasive species and bottom fishing.
368 Defeo, et al. 2009
369 National Research Council of the National Academies 2011

                                            Effects of Different Types of Development on the Environment
                                                                           that are currently
                                                                           considered safe from
                                                                           flooding, storms, or
                                                                           wildfires could become
                                                                           vulnerable as the
                                                                           climate changes.

                                                                           Communities have
                                                                           used a variety of
                                                                           approaches to
                                                                           safeguard farmland,
                                                                           forests, coastal zones,
                                                                           and other types of
                                                                           open space.370 In the
                                                                           most direct approach,
                                                                           local, regional, state,
                                                                           and federal agencies
                                                                           acquire parks,
                                                                           recreation areas,
                                                                           forests, wildlife
refuges, and wilderness areas to ensure their long-term protection and maintenance. Limited resources
and political considerations preclude most governments from owning all critical land areas they might
want to preserve. Often communities supplement these efforts with regulatory approaches that
discourage or limit the amount and type of development that can occur in sensitive areas. For example,
many communities use zoning to direct development to certain areas and to establish allowable
development densities. Local or regional comprehensive plans can also encourage development in
certain places; for example, by designating which areas are eligible for public infrastructure. In addition,
many communities complement direct ownership and  regulation with incentives to promote private
stewardship of important natural resources. Tax policies can provide financial incentives that encourage
or discourage development in certain areas. Streamlined permitting and review processes for projects in
already developed areas can also encourage development in those locations.

A review of how effectively these types of public policies protect open space found that while robust
analyses of different policies are generally lacking, communities that have been most successful in
safeguarding their sensitive lands have multiple, complementary policies  aimed at achieving this goal.
Coordination across different levels of government and jurisdictions at a regional scale is also critical for
success. Finally, the review also found that meaningful involvement of residents and other stakeholders
Exhibit 4-1: A mature bottomland hardwood forest filled with native plants. The
Blockston Branch of theTuckahoe Creek at the Atkins Arboretum in Ridgeley, Maryland,
provides a wealth of ecosystem services, including water and air purification and habitat
for quail, bluebirds, foxes, and turkeys.
Photo source: EPA
   Bengston, Fletcher, and Nelson 2004

Effects of Different Types of Development on the Environment
in developing a community vision and the tools to implement it is an essential component of effective
land preservation strategies.371

4.1.2   Importance of Infill Development
Infill development occurs in locations where
some development  has already taken place
and infrastructure is already available. It
includes redeveloping old buildings and
facilities and putting undeveloped space in
developed areas into productive use. Infill
development reduces development
pressure on outlying areas, helping to
achieve the goal of safeguarding critical
lands. When infill development occurs near
existing transit infrastructure or near
employment centers and other destinations,
it can also help slow growth of or even
reduce VMT by reducing the amount people
need to drive.372 In fact, development's
location relative to the surrounding places
people want to go is one of the most
important determinants of how much
people travel by car (see Section 4.2.5).
Exhibit 4-2: Infill development. Developers of the Matrix Condos
in Washington, D.C., converted a long-abandoned former auto
dealership into a mixed-use project by building on adjacent
empty lots and adding two stories to the existing building, set
back from its facade. The condo residents are within walking
distance of downtown, a grocery store, multiple restaurants, and
other local businesses. A bus stop is right outside their front
Photo source: EPA
Infill Potential
The amount of land available for infill is
difficult to quantify. Many cities in the
United States have populations far from their peak, suggesting that existing infrastructure and space in
these places could accommodate more people. The number of abandoned lots and buildings only
underscores this observation. A 2009 survey of mayors from 53 cities estimated the number of vacant
and abandoned properties. The highest estimates were 15,078 in Las Vegas; 13,500 in St. Louis; 8,306 in
Louisville, Kentucky; 7,700 in Port St. Lucie, Florida; and 7,000 in Cape Coral, Florida. The lowest
estimates were 25 in Stow, Ohio; 21 in Menlo Park, California; and 11 in Bell Gardens, California.373

The U.S. Census collects information on the number of vacant housing units (Exhibit 4-3). At 7.9 percent,
Connecticut has the lowest rate of vacancy, while both Maine and Vermont have the highest rates of
more than 20 percent, likely due to a high  percentage of seasonal, recreational, or occasional use
   Bengston, Fletcher, and Nelson 2004
   Landis, et al. 2006
   United States Conference of Mayors 2009

                                            Effects of Different Types of Development on the Environment
South Carolina
New Hampshire
North Carolina
West Virginia
New Mexico
North Dakota
Total Housing
Units in 2010
South Dakota
Rhode Island
District of Columbia
New York
New Jersey
Total Housing
Units in 2010
              Exhibit 4-3: Percentage of housing units vacant, 2010.
              Source: U.S. Census Bureau Housing Characteristics: 2010 2011

A 2006 analysis estimated that California had nearly half a million potential infill parcels, defined as
vacant or underused lots within existing city boundaries or in unincorporated places with at least 2.4
residential units per acre.374 Together, these parcels occupied 220,000 acres. Maintaining existing
residential densities in neighborhoods, these sites could accommodate about 1.5  million additional
housing units, 25 percent of the state's projected need over 20 years. If residential densities increased
to levels compatible with existing residential character (depending on location) and higher-density
housing was built near transit, the researchers estimated  that an additional 4 million housing units could
be accommodated on existing infill sites. This scenario would meet 100 percent of the state's projected
need over 20 years and avoid development on 350,000 acres of undeveloped land.

An EPA analysis of residential construction trends supports the idea that many metropolitan regions can
support a significant  amount of infill development.375 Among 20 metropolitan regions, 21 percent of
new home construction between 2000 and 2009 occurred in previously developed areas. In some
regions, the figure exceeded 60 percent (Exhibit 4-4).
   Landis, et al. 2006
  1 EPA, Residential Construction Trends in America's Metropolitan Regions 2012

Effects of Different Types of Development on the Environment
      Percentage of new homes that are infill
   Exhibit 4-4: Percentage of new home construction that is infill, 2000-2009.
   Image source: EPA, Residential Construction Trends in America's Metropolitan Regions 2012
Certain types of underdeveloped land, greyfields, brownfields, and hazardous waste sites, have received
significant attention as both problems and opportunities because their redevelopment has the potential
to provide multiple community benefits. As noted in Section 3.2, reliable national area data for these
types of sites are not available.

Environmental Benefits of Cleaning up Brownfields and Hazardous Waste Sites
The cleanup and redevelopment of brownfields and hazardous waste sites can bring substantial
environmental and health benefits. The most obvious environmental benefit of land cleanup is the safe
disposal of environmental contaminants. Land cleanup activities also provide the opportunity to reuse
the land for new development, removing pressure to develop in natural areas that have important
ecological functions. Land reuse prevents many of the greenhouse gas emissions that would come from
the construction of new transportation and other infrastructure necessary to serve the development.
Land cleanup can also provide opportunities to reuse and recycle construction and demolition debris
from buildings in ways that protect human health and the environment. Reusing materials and land
avoids the need to devote any additional land to waste disposal. Finally, certain site remediation
techniques can provide additional environmental benefits. For example, adding organic matter to soil
increases carbon dioxide sequestration, enhances vegetation growth, and can even make productive use

                                           Effects of Different Types of Development on the Environment
of what might otherwise be a waste product.376Greyfield, brownfield, and hazardous site
redevelopment can dramatically improve environmental quality and community life, since undeveloped
sites can be health threats or discourage further investment in the area. Investments in site assessment
and cleanup can encourage additional investment in cleanup and redevelopment nearby, further
improving environmental outcomes.

4.1.3   Benefits of Focusing Development Around Transit Stations

Transit systems with fast, frequent, and dependable service attract riders and can reduce VMT, reducing
air pollutant and greenhouse gas emissions. A bus carrying 20 passengers consumes only about one-
third of the energy that would be needed if each passenger drove a private vehicle.377 Transit also
provides mobility to people who cannot or choose not to drive, which can help low-income people find
and keep jobs and helps older residents maintain their independence when they can no longer drive.

Transit-oriented development (TOD) locates housing,  shopping, and employment near transit stations. It
makes transit a more convenient and practical form of transportation and can be a catalyst for other
land use changes that benefit the environment. A review of the literature found that under certain
conditions, light rail could increase the density of development. The best conditions for spurring
development occur when light rail is constructed in areas that are growing, when it significantly
improves access to the areas it serves, when there is developable land around stations, and when local
land use policies support TOD.378

Several  studies have attempted to quantify the impacts of TOD on transit use. For example, a study of
26 TOD projects in California found that people living within a half-mile of a rail station were about four
times as likely to commute by rail as those living between one-half and 3 miles away and six times as
likely to commute by rail as those living more than 3 miles from the station. Residents who are inclined
to use transit often choose to live near a transit station, which explains part of the difference.  However,
other important factors included whether residents were able to access jobs easily by highways (which
decreases transit use) and whether there was a walkable street grid at places residents can reach by
transit (which increases transit use).379 In  addition to the location of housing, the location of
employment is also important. Employees who work at locations near rail  stations were three times as
likely to commute by public transportation as those working at places without rail access. Frequent bus
service from stations to office sites,  employer subsidies for transit costs, and scarcity of parking were
also important factors in increasing transit use.380
   EPA, Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices
   A car has an energy intensity of 5,342 Btu per vehicle mile. Twenty drivers would therefore use 106,840 Btu per
mile compared to 35,953 Btu per mile if all rode together on a bus (Davis, Diegel, and Boundy 2012, Table 2.12).
378 Handy 2005
379 Cervero 2007
380 Cervero 2006

Effects of Different Types of Development on the Environment
Portland, Oregon, has used TOD as one of many
policy tools to encourage transit use (Exhibit 4-5).
A study of commuting behavior in census block
groups in Portland found that commuters living
near light rail or bus service in areas with a higher
proportion of mixed use were more likely to use
public transit, walk, or bike to work. Commuters
closer to freeway interchanges in areas with a
higher share of land used for single-family homes
were more likely to drive alone. However, the
study found no correlation between commuting
behavior and TOD, although it measured the
degree to which an area's development was
transit oriented based only on whether it was
within one mile of a light rail station and either
housing or job density.381 A study based on
resident surveys in Portland showed that those
living in TODs were more than 2.5 times as likely
to commute by transit as other Portland  residents.
Nearly 20 percent of transit commuters living in
TODs had switched from other modes of travel,
while just 4 percent of commuters living in TODs
switched from transit to another mode of
A more comprehensive evaluation of TOD across cities looked at 17 TOD projects of different sizes in
four areas of the country: Philadelphia and northeast New Jersey;  Portland, Oregon; metropolitan
Washington D.C.; and the San Francisco Bay Area's East Bay. Researchers compared actual vehicle trip
rates with those predicted using the Institute of Transportation  Engineers manual, which is often used to
project local traffic and parking impacts and set impact fees for development projects. Across the 17
TOD projects, about 47 percent fewer trips occurred than projected. The largest reductions in vehicle
travel occurred at TOD projects closest to central business districts with the highest residential

A 2008 review of the literature found that people living in TODs are two to five times more likely to use
transit for commuting and nonwork trips than other people living in the same region.  Many of the
transit users at TOD sites previously used transit and presumably chose to live in a TOD for its transit
accessibility. However, TOD increased transit use by up to 50 percent for people who had no prior
Exhibit 4-5: Mixed-use, multifamily building.
Developments on the streetcar line in the Pearl District of
Portland, Oregon, give residents easy access to
universities, a major hospital, and the central business and
shopping districts.
Photo source: Kyle Gradinger via flickr.com
  1 Dill 2008
  ' Arrington and Cervero 2008

                                           Effects of Different Types of Development on the Environment
transit access. Transit use varies considerably across regions, determined primarily by how well transit
links destinations.384

In addition to the location of development relative to transit, the location of transit itself is important.
The effects of transit on overall development patterns depend on where it is located and what
development patterns it serves.385 For example, transit can make it convenient for people to live far
from where they work and lead to new development in previously undeveloped land. Building public
transit that serves already-developed areas can help attract growth to areas where it can help mitigate
overall environmental impacts from development rather than create new ones.

4.2    How We Build

How we build also influences development's impact on the environment and human health. The way we
build our cities and towns, including the details—the scale and relationship of buildings, blocks, streets,
and public places—determines how close homes are to workplaces, how many destinations can be
reached comfortably and pleasantly by walking or biking, and whether frequent bus or rail transit is
practical. The design and connectivity of transportation networks can either make it easy to get around
by walking, biking, transit, and short driving trips, or require people to drive for every trip. Green
design—of neighborhoods, streets, and buildings—can help clean and manage stormwater, use energy
and water more efficiently, and improve air quality.

The relationship between the built environment and travel behavior  is complex. An extensive body of
literature attempts to measure the impacts of the built environment on travel behavior, producing not
just multiple reviews but also reviews of the many reviews.386'387 Measuring the effects of various land
use characteristics on VMT is challenging because these characteristics change slowly and have delayed
effects. It is also difficult to identify treatment and control groups for rigorous experimental design.388 In
addition, differences in methodology, units of analysis, scale of study, and the characteristics considered
make it difficult to draw overall conclusions.389

In spite of indications that many individual components of the built environment have relatively small
effects on travel behavior,390 small effects of individual variables can  be cumulative.391 These effects
tend to have local impacts at first392 that increase overtime.393 Many of the environmental challenges
we face today require a comprehensive approach in which strategies with fairly modest results can
384 Arrington and Cervero 2008
385 Handy 2005
386 Gebel, Bauman, and Petticrew 2007
   Ewing and Cervero 2010
388 Salon, etal. 2012
389 Bhat and Guo 2007
390Salon, etal. 2012
391 Kuzmyak, et al. 2003
392 Kuzmyak, et al. 2003
393 Dulal, Brodnig, and Onoriose 2011

Effects of Different Types of Development on the Environment
cumulatively play important roles in protecting our environmental resources and ensuring the needs of
future generations can be met.

When interpreting research on the built environment, one important factor is the extent to which
people choose to live in neighborhoods based on their travel options. Results that appear to suggest
that the built environment could change people's inclination to use transit, bike, or walk might instead
mean that the built environment merely makes it possible to use these transportation options.39'
Researchers have called the tendency of people to live in places that accommodate their travel
preferences self selection. If self selection alone can explain an association between the built
environment and travel behavior, then land use changes are likely to change travel behavior only to the
extent of the unmet demand for neighborhoods that can accommodate different forms of travel—and
                                                                 research has demonstrated that
                                                                 indeed unmet demand for more
  Exhibit 4-6: The Castro District, San Francisco. The Castro District is one of
  the city's most vibrant and cohesive neighborhoods. Small and medium-sized
  single-family Victorian homes and small apartment buildings create a
  compact neighborhood where residents can walk to shops, businesses, parks,
  and movie theaters.
  Photo source: EPA
                                                                 neighborhoods exists.
studies have documented self-
selection effects and highlight the
importance of controlling for this
factor when evaluating
associations between the built
environment and travel
behavior,397'398 although some
studies have found that its
impacts are modest or non-
existent.399'400 There is some
evidence that elements of the
built environment that improve
walkability and transit
accessibility actually have smaller
impacts on the travel behavior of
people who seek walkable,
transit-accessible neighborhoods
than on the travel behavior of
people who do not prioritize
   Handy 2005
  ' Levine, Inam, and Torng 2005
  ' Levine and Frank 2007
   Cao, Mokhtarian,  and Handy 2009
  ! Bhat and Guo 2007
  ' Chatman 2009
  1 Ewing and Cervero 2010

                                             Effects of Different Types of Development on the Environment
these attributes because people who prefer to walk or take transit tend to do so regardless of their
neighborhood characteristics.401

Describing discrete components of the built environment can be challenging because factors overlap
and variables correlate with one another. Thus, many studies have similar findings, although the
variables they investigate vary. The following sections cover several attributes of the built environment
that are relatively well studied across the United States:402

    •   Compact development.
    •   Mixed-use development.
    •   Street connectivity.
    •   Community design.
    •   Destination accessibility.
    •   Transit accessibility.
    •   Green building.

4.2.1  Compact Development

Compact development generally means using less land area to satisfy the needs of a population. The
more compact a community, the less land is needed for development, reducing environmental impacts.
In more compact areas, people  can travel shorter distances for everyday activities, and it is easier to
walk or bike to those
destinations. In addition, compact
development makes public
transit, sidewalks, and bike paths
more practical and cost-effective
because destinations are closer

Many studies have tried to
investigate the effects of compact
development using population
density as a  metric.  However,
higher population density rarely
occurs without at least some
other confounding factors, such
as a mix of land uses, access to
public transportation, and the
Exhibit 4-7: Compact residential neighborhood. Many city streets in
Philadelphia are lined with single-family rowhouses and small apartment
buildings. Narrow streets and shade trees make walking to nearby
commercial areas convenient and pleasant.
Photo source: EPA
   Chatman 2009
402 This literature review excluded research based solely on data from locations outside of the United States,
except when geographic location is unlikely to affect the results (e.g., for performance of building energy efficiency

Effects of Different Types of Development on the Environment
presence of sidewalks and other characteristics that would likely influence how people choose to travel.
Indeed, density is often a prerequisite for community characteristics such as better transit service or a
higher diversity of land uses.403 Public transit is more cost-effective the more people and destinations it
can serve in a given area. In addition, more people in a given area can support more types of businesses
and institutions. This section looks at studies that have attempted to isolate the effects of compact
development on the environment.

Vehicle Miles Traveled
The density of people in a community—i.e., the number of people that live per unit of land—is a good
indicator of how much people will drive and how much they will get around by foot or by bike. Density is
strongly correlated with many of the characteristics that make driving long distances unnecessary and
make other forms of transportation appealing alternatives to driving: mixed residential, commercial, and
institutional areas; destinations situated close together; and sidewalks.404 In general, the greater the
population density of an area, the less the area's residents tend to drive.405

The majority of the research on compact development's effect on the environment looks at the issue by
considering its influence on VMT and the negative environmental and human health effects associated
with vehicle travel. Reviews of the literature have noted for decades the association between density
and vehicle travel, measured by both the number of per capita trips and VMT.406 As expected, along with
the decline in VMT, higher densities are associated with increases in other forms of travel, particularly
transit and walking.

The National Research Council considered  the issue in a 2009 report.407 Based  on a review of the
literature, this report confirmed that higher residential and employment density result in less driving
and more transit use and walking. After accounting for socioeconomic factors  and adjusting for self
selection, the report concluded that doubling residential density  across a metropolitan region could
reduce household VMT by between 5 and  12 percent. Reductions of as much as 25 percent would be
possible if increased residential density occurred with other changes such as increased employment
density, improved public transit  service, a mix of land uses, and other changes that encourage
alternatives to driving such as  parking demand management and street design that encourages walking
and biking. The report noted that the air quality benefits from reduced VMT would occur in addition to
other environmental benefits from more compact development,  such as more land conservation  and
reductions in stormwater runoff.

Other, more recent studies and reviews have confirmed the general pattern that increased density
reduces VMT. For example, a 2012 meta-analysis of studies on the relationship between density and
travel behavior in the United States and Europe confirmed the decline in VMT with higher density holds
403 Kuzmyak, et al. 2003
404 Kuzmyak, et al. 2003
405 Transportation Research Board of the National Academies 2003
406 Kuzmyak, et al. 2003
407 National Research Council of the National Academies, Driving and the Built Environment 2009

                                            Effects of Different Types of Development on the Environment
for both regions, although it is considerably stronger in Europe.408 However, the size of the effect is still
uncertain. One study analyzed the relationship between VMT and both population and employment
density across 370 urbanized areas in the United States.409 A 10 percent increase in population density
was associated with a 3.8 percent decrease in VMT per capita, while employment density had more
modest effects. A modeling study considered how VMT would change in response to changes in
development patterns, incorporating information about where people choose to live to correct for self
selection. The model results show that increasing residential density, jobs per capita, and per capita
expenditures on public transit operations each by 10 percent could  reduce annual VMT from 22,182
miles to 17,782 per household, a reduction of about 20 percent.410

The most recent reviews note that high residential and employment density are most strongly
associated with reduced VMT when coupled with
other factors such as mixed land uses and public
transit service.411 Such factors that tend to co-occur
with density appear to be of considerable
importance. Density by itself generally shows only
relatively modest effects. A meta-analysis412 of
travel literature that isolated individual measures of
the built  environment found that after controlling
for all other measures, population and job density
actually had the weakest association to travel
behavior among those that are significant.413 A
minimum population density is necessary for many
of the other factors that influence travel behavior
(discussed in the following sections), but alone, it is
likely not sufficient.

Vehicle Miles Traveled and Air Pollution
Several studies have considered the link between
density, VMT, and air pollution. For example, a
study of 45 of the largest metropolitan regions over
13 years found a positive correlation between a
quantitative sprawl index and both emissions of
ozone precursors and the number of high ozone
Exhibit 4-8: Heavy traffic. Interstate 94 in Minneapolis
carries commuters to and from downtown, contributing
air pollution to the entire region.
Source: drouu via stock.xchng
 u° Gim 2012
   Cervero and Murakami 2010
410 Chattopadhyay and Taylor 2012
411 Dulal, Brodnig, and Onoriose 2011
412 Meta-analyses use summary statistics from individual primary studies as the data points in a new analysis. They
help establish overall relationships when the results of the individual studies were inconsistent or their study
designs, statistical techniques, and/or study populations varied (Gim 2012).
413 Ewing and Cervero 2010

Effects of Different Types of Development on the Environment
days.414 The study found that the least compact regions (those scoring highest on the sprawl index415)
had 60 percent more high ozone days than the most compact regions. Of the variables included in the
sprawl index, density was most strongly associated with this effect: each standard deviation increase in
density was associated with an average of about 16 fewer high ozone days per year. The study found
that the positive correlation between the sprawl index and the number of high ozone days held even
when controlling for annual emissions of ozone precursors. Since transportation is a significant
contributor to ozone precursor emissions, the study suggests that lower VMT in more compact
metropolitan regions cannot entirely explain the lower levels of ozone air pollution.

Another study estimated the carbon dioxide emissions of 100 of the largest metropolitan regions of the
United States.416 Per capita emissions varied considerably across regions, with the highest emitting
region (Bakersfield, California) emitting almost 2.5 times as much carbon dioxide per resident as the
lowest-emitting region (New York, New York/New Jersey). Differences were even greater when
emissions were calculated based on gross metropolitan product, the metropolitan region's equivalent of
gross domestic product. Emissions per gross metropolitan product in the highest-emitting region
(Riverside, California) were almost five times the emissions in the lowest-emitting region  (Bridgeport,
Connecticut). Analysis of differences showed that the amount of trucking activity in a metropolitan
region could explain much of this variation. However, overall population and  employment density, as
well as how people and jobs were distributed across the region, also helped explain differences among
regions. A higher density of people and jobs per acre was associated with lower carbon dioxide

Development that is more compact can reduce greenhouse gas and other air pollution emissions, not
just by reducing travel, but also by reducing the amount of infrastructure needed. Smaller, more
compact buildings use less energy for heating and  cooling. A study compared the greenhouse gas
emissions associated with a high-density residential area in downtown Toronto with a low-density
suburb. The study included emissions associated with transportation, infrastructure construction, and
building operations. It found that the low-density neighborhood was between two and 2.5 times more
energy intensive per capita than the high-density neighborhood.417

A 2008 paper reviewed  four different types of literature on the relationship between development
patterns and travel behavior: studies that aggregated travel  behavior at a regional level, studies that
looked at individual travel behavior, regional simulations, and project-level simulations.418 When enough
data permitted, the authors conducted a meta-analysis of the results. The results suggested that within
a region, compact development in  combination with other strategies—such as increasing land use mix
and ensuring that destinations are easily accessible from around the region—could reduce VMT
414 Stone 2008
   According to the modified sprawl index used in this study, higher scores denote higher levels of sprawl, unlike
other studies discussed earlier in which higher scores denote lower levels of sprawl.
416 Southworth and Sonnenberg 2011
   Norman, Maclean, and Kennedy 2006
418 Ewing, Bartholomew, et al. 2008

                                            Effects of Different Types of Development on the Environment
significantly, by as much as 20 to 40 percent. Nationally, total VMT could be reduced by 10 to
14 percent, leading to a 7 to 10 percent decline in total U.S. transportation carbon dioxide emissions.

Regional Versus Neighborhood Air Quality
In addition to regional air quality, communities are concerned about neighborhood-level air quality.
Some studies have looked within regions at population-weighted air pollution exposures, which
represent the average exposure level of the area's population.419

The relationship between the location of pollution sources and air quality impacts is complex. Air
pollutants have different sources, concentration patterns around sources, and sensitivity to climate and
weather conditions. Primary pollutants are emitted directly to the atmosphere, while secondary
pollutants result from chemical reactions in the atmosphere. Concentrations of some pollutants are
highest near the source and tend to drop as distance from the source increases. Pollutants with this
pattern include primary pollutants, such as carbon monoxide, and those secondary pollutants that form
quickly, such as nitrogen dioxide. Concentrations of other pollutants tend to have a more even
distribution because they are transported downwind over wide areas. Pollutants with this pattern
include those secondary pollutants such as ozone that can take hours to form as their precursors move
downwind and undergo chemical reactions.420 As a result, local concentrations of this type of pollutant
might not be well-correlated with local emissions  of its precursors. For example, the highest ozone
concentrations are often downwind of areas where VOC and NOX emissions are highest.421
Understanding these differences is critical to evaluating studies examining the relationship between
compact development and the concentrations of different air pollutants.

One study investigated the relationship between compact development and regional and neighborhood
levels of ozone and PM2.5 in 80 U.S. metropolitan regions.422 It found that regional ozone concentrations
were lower in more  compact areas (as measured by a sprawl index), but population-weighted ozone
exposures were higher because people tended to be concentrated around air quality monitors  recording
higher pollution levels. Although the average regional concentration of PM2.5 was not correlated with
the sprawl index, population-weighted exposures to PM2.5 were higher in compact regions, as was the
case for ozone. The study also found that neighborhoods with higher percentages of minority and poor
residents had higher concentrations of both ozone and PM2.5. This study did not examine how
population influenced pollution levels, so it is unclear from this study whether differences in vehicle
activity, the timing and location of emissions, the distance between emissions and people, or other
factors might explain the results.
   Population-weighted air pollution exposures are determined by multiplying the population in the
"neighborhood" around each air quality monitor (e.g., the population living within a half mile of a monitor) by the
monitor's reading for every monitor in an area, adding those results, and then dividing by the total population of
the area.
420 Marshall, McKone, et al. 2005
421 Other complex interactions between the precursors of ozone and secondary PM components influence the
interpretation of these studies. For example, in many urban centers, emissions of NOX reduce concentrations of
ozone within the city, but raise concentrations in locations downwind.
422 Schweitzer and Zhou 2010

Effects of Different Types of Development on the Environment
Another study of 111 U.S. urban areas found that population-weighted exposure to PM2.5 and aggregate
pollutant levels were higher in areas with higher population density.423 However, population-weighted
ozone exposure was not associated with population density in this study, and population centrality (see
Section 4.2.5), another common attribute of compact regions, was associated with lower population-
weighted exposure to PM2.5 and ozone. Thus, while development patterns can clearly influence air
pollution, compact development encompasses several attributes,  and density alone might not be its
best measure.

There are several considerations to take into account when reviewing the results of these and other
studies. First, it is important to consider the quality and purpose of the air quality monitoring data that is
the basis of findings for neighborhood population exposure. In the study of 111 urban areas, the air
quality data used for ozone and  PM2.5 were from 1990 and 2000, respectively.424 Since those data were
collected, many of the areas in this study have achieved significant emission reductions despite
increasing population. Furthermore, the majority of the vehicles on the road in 1990 have been replaced
with vehicles meeting more stringent emission standards. More recent data could lead to different
results and conclusions because many air pollutant effects are non-linear. In addition, the air quality
monitoring networks in the United States have been designed to meet statutory and regulatory
objectives425 rather than to support this type of research. In fact, the study on the relationship between
compact development and regional and neighborhood levels  of ozone and PM2.5 in 80 U.S. metropolitan
regions discusses several methods of sampling and grouping existing data to address such limitations.426
Finally, historical development patterns mean that residential neighborhoods are often located near
ports, heavy industry, and other major emissions sources. The relationship between population-
weighted pollution exposures and the compactness of a region reflects in part this history and does not
imply causality. All of these factors complicate the interpretation of  results of these studies.

One useful conclusion from this  body of research is that better air quality outcomes could be achieved if
communities coupled compact development with careful consideration of that development's location
within a region. Locating new, compact development away from major sources of emissions, such as
freight corridors or power plants, would help minimize exposure to these pollution sources while
reducing pollution regionally. For pollutants where air quality concentrations decrease with distance
from their source, relatively small adjustments in the location or design of development could have
large effects on air pollution exposures. When advocating for more compact development to help
reduce VMT,  preserve habitat, and increase physical activity, planners could take differences in
neighborhood air quality into account, where data are available to evaluate potential locations or better
site design.

In addition to considering the location of new compact development relative to emissions sources,  other
strategies can help avoid high neighborhood-level concentrations. For example, a higher proportion of
423 Clark, Millet, and Marshall 2011
424 Clark, Millet, and Marshall 2011
   EPA, The Ambient Air Monitoring Program n.d.
426 Schweitzer and Zhou 2010

                                            Effects of Different Types of Development on the Environment
lower-emitting vehicles in city centers and use of indoor air filtration systems reduce individual air
pollution exposures.427 Strengthening the impact of density on VMT through complementary urban
design features could also help decrease both regional pollution levels and per capita exposure.428
Sections 4.2.2 through 4.2.6 discuss the types of strategies that research has shown to strengthen this
relationship. Improving air quality for the largest number of people would likely require additional
emissions reductions from vehicles and other sources as well as supporting denser, mixed-use districts
where walking,  biking, and transit use reduce the need to drive.429

Heat Island Effect
As discussed in Section 3.5, the heat island effect is associated with the built environment. Locating tall
buildings near one another can contribute to the heat island effect by limiting wind circulation and
creating large areas of impermeable surfaces that
absorb the sun's heat. However, in other ways,
building compactly to minimize developed area could
potentially lessen the heat island effect. Compact
development reduces  impervious area that can absorb
the sun's heat and prevent evaporative cooling. It does
this in several ways, including by using taller buildings
that require less roof per amount of living space,
smaller lots that require fewer miles of roads and
sidewalks, and homes  nearer to the street to reduce
driveway lengths.
One study of the Atlanta region looked at how single-
family residential density affected an indicator of
surface heat island formation.430 The results showed,
somewhat counterintuitively, that smaller,  higher-
density lots had less surface heat island formation than
larger, lower-density lots, which tended to  have more
vegetative cover after controlling for the number of
bedrooms per home, orthe number of people the
home was designed to accommodate. The amount of
lawn and landscaping in an area, which is strongly
correlated with lot size, was actually a stronger
predictor of surface heat island formation in urban
areas than the amount of impervious cover, although
both were important. A 25 percent  reduction in impervious cover of a single-family lot was associated
with a 16 percent reduction in surface heat island formation. If combined with a 25 percent reduction in
Exhibit 4-9: Cooling off in Centennial Olympic Park,
Atlanta. The heat island effect can make cities
uncomfortably hot in the summer unless there are
places to cool off.
Photo source: Patrick Fitzgerald via flickr.com
   Marshall, Brauer, and Frank 2009
  ! Marshall, McKone, Deakin, and Nazaroff 2005
  ' Frank and Engelke 2005
  ' Stone and Norman 2006

Effects of Different Types of Development on the Environment
lawn and landscaping area (i.e., smaller lot sizes), the reduction in surface heat island formation reached
28 percent.

Research has also shown a link between the built environment and extreme heat events, which the heat
island effect exacerbates. Over five decades, the number of extreme heat events in 53 U.S. metropolitan
regions increased by about 0.2 events per year overall, leading to about 10 additional events per city in
2005 compared to 1956.431 A comparison across these metropolitan regions showed that the most
sprawling (the top quartile based on a sprawl index) had a rate of growth in heat events more than twice
that of those in the bottom quartile. The most compact metropolitan regions had an average of 5.6
more extreme heat days in 2005 compared to 1956, while the least compact had 14.8 more days, after
controlling for climate zone, metropolitan population size, and the rate of metropolitan  population
growth.  Lower rates of tree canopy loss in more compact areas might contribute to this  difference. The
study found that between  1992 and 2001, the most sprawling metropolitan regions had twice the rate
of tree canopy loss as the most compact regions.

Water Quality
Compact development also influences water quality. Section 3.3 discussed the impacts of development
and its associated impervious cover on downgradient432 water resources and water quality. Since
compact development means less land is needed for a given number of people,  it can play an  important
role in protecting land from degradation and preserving downgradient water quality.

A model to  evaluate pollutant loadings in stormwater runoff under different residential  densities
showed  that as the number of homes per acre increases,  so do the total amount of stormwater runoff
per acre and the total pollutant loadings per acre, including total nitrogen, total phosphorous, and total
suspended solids.433 However, the model also showed that 100 homes developed at a density of eight or
more per acre produced less total stormwater runoff and pollutant load than 100 homes developed at a
typical suburban density of three to five homes per acre.  In other words, for a constant number of
households, denser development generates less total stormwater runoff because it affects a smaller
area. EPA found similar results in a modeling study that showed that for a given amount of
development, higher-density development  produces less runoff and less impervious cover and affects
less of the watershed than low-density development.434

4.2.2  Mixed-Use Development

Density alone might be less important than the mix of uses in an area, which affects distances between
destinations and the ability to walk or bike between them. Standard zoning separates uses into distinct
zones for residential, commercial, or industrial uses. In contrast, mixed-use development puts land uses
with complementary functions close together. Complementary uses include housing, shopping and
431 Stone, Hess, and Frumkin 2010
432 Downgradient refers to the direction that groundwater flows.
433 Jacob and Lopez 2009
434 EPA, Protecting Water Resources with Higher-Density Development 2006

        Effects of Different Types of Development on the Environment
Exhibit 4-10: Main Street in Montpelier, Vermont. A mix of shops, offices,
and apartments in the city's downtown create a neighborhood where
residents are close to a lively arts and music scene, restaurants, and
Photo source: EPA
entertainment, offices,
restaurants, schools, and houses
of worship—any destinations to
which people regularly travel.

When an office building also
contains shops and restaurants,
the infrastructure that supports
the building—the roads  and
parking lots—is used for more of
the day. Office workers use the
parking lot during the day.
Restaurant and theater patrons
use the parking in the evenings.
The alternative is two sets of
roads and parking lots—one  set
serving office buildings and another serving retail and entertainment areas.

Mixed-use development can occur on different levels: site-specific, neighborhood, or regional. On a site,
individual buildings or complexes can incorporate a variety of uses. For example, a single building might
include apartments, offices, and shops. At the neighborhood level, mixed-use development refers to the
arrangement of different uses across several blocks or acres of land so that they are connected. At the
regional level, mixed-use policies often aim to balance jobs and housing so that people can live closer  to
their places of employment.

At any level—building, neighborhood, or region—the travel-related environmental  effect of mixing uses
is similar.  By making it easier for people to walk, bike, and use transit to reach destinations, mixed-use
development patterns allow people to drive less if they choose. Reductions in VMT can lead to
decreases in automobile emissions, thereby improving air quality.

Mixing land uses can reduce  VMT in several ways:

    •    Trip lengths—By putting destinations closer together, a mix of land uses can minimize travel
        distances and improve access to jobs, services, or recreation.

    •    Mode choice—Putting destinations closer together allows trips to be made by walking and
        bicycling rather than by driving cars. Even if people drive to one destination, they can walk, bike,
        or use transit to get to another nearby. Mixing jobs and housing in an area can reduce commute
        distances, making walking, biking, and transit more practical. Alternatively,  mixing jobs or homes
        with shops and businesses lets workers take care of errands during the day, without needing a

    •    Vehicle ownership—Easy walking and biking access to jobs and shopping reduces the need to
        own a car to  meet daily needs, reducing VMT.

Effects of Different Types of Development on the Environment
As noted in Section 4.2.1, much of the literature on compact development shows that the effect of
density in reducing VMT is much stronger when combined with other characteristics, including mixed
land uses.435 Fewer studies have attempted to isolate the effects of a mix of uses, as a factor influencing
VMT, from other characteristics with which it is generally associated, such  as having multiple
destinations easily accessible from around an area.436 In one example, a study of Portland, Oregon,
neighborhoods showed that the more diverse the land use mix, the  lower the rates of commuting by
driving alone. The effect was stronger for mixed-use development in residential areas than job

Researchers analyzing data from the San Francisco Bay Area found that every 10 percent increase in the
number of jobs that are in the same occupational category as a person currently works and that are
located within 4 miles of that person's home was associated with a 3.3 percent reduction in  commuting
VMT. Every 10 percent increase in the number of retail and service jobs within 4 miles was associated
with a 1.7 percent reduction in VMT for shopping and services.438 Factoring in estimates of the amount
of VMT attributable to commuting (37 percent) versus shopping and services (43 percent) in the San
Francisco Bay Area, improved access to jobs in  the same occupational category as the job one currently
holds was associated with a 73 percent greater reduction in VMT than improved access to shopping and

In a more comprehensive analysis, researchers studied 239 mixed-use developments across six U.S.
metropolitan regions for which good household travel data were available: Atlanta; Boston;  Houston;
Portland, Oregon; Sacramento, California; and  Seattle. The results showed that on average, three out of
every 10 trips in a mixed-use development are  relatively short and remain  entirely within the
development, adding no traffic to surrounding  streets. Mixed-use developments that had the largest
share of internal versus external trips had the greatest diversity of activities available within the
development and/or were in walkable areas with good transit access. The  more centrally located the
development is and the more jobs are close by, the lower the overall VMT of residents.440 Other
research has shown that some portion of the trips occurring within mixed-use developments likely
would not have occurred if not for their relative ease.441 Thus, the trip reduction benefits of  mixed-use
development might be overestimated if not accounting for this effect. However, mixed-use
development has benefits beyond reducing VMT. Any additional trips in mixed-use communities are
likely caused by and in turn contribute to a vibrant pedestrian  atmosphere.
   National Research Council of the National Academies, Driving and the Built Environment 2009
436 Kuzmyak, et al. 2003
437 Jun 2008
438 VMT for shopping and services included any trip that involved travel to at least one shopping, service, or eating
destination that did not also include a work destination. Both VMT and vehicle hours traveled included only time
spent in a personal vehicle.
439 Cervero and Duncan 2006
440 Ewing, Greenwald, et al. 2011
441 Sperry, Burris, and Dumbaugh 2012

                                             Effects of Different Types of Development on the Environment
A review of the literature found a consistent positive relationship between the amount that people
walk442 as a means of transportation and population density, the distance to non-residential
destinations, and the degree to which land uses are mixed, all of which suggest the importance of
destination proximity in explaining walking behavior.443 A more recent study of an ethnically diverse
sample of 5,529 adults from six U.S. cities found that when population density and the amount of land
devoted to retail uses increases from the fifth percentile to the 95th percentile, the probability of walking
more than 150 minutes per week, compared to getting no exercise, increased from 66 percent to
95 percent.444 Other research suggests that the proximity of specific land uses is likely also important for
determining the amount that people walk. A study in Montgomery County, Maryland, found that in
addition to land use diversity, the number of bus stops, grocery stores, offices, and retail stores within
half a mile from home were significant predictors of how likely people were to walk to get to their daily

4.2.3  Street Connectivity
Many communities contain a
hierarchy of dead-end or cul-de-sac
local streets with strictly residential
uses that lead to collector streets
where all retail and commercial
activity occurs (Exhibit 4-11). These
collector streets lead to major
arterials that connect communities
to others via  highways. Some
communities are bounded by
railroad tracks, lakes, or other
physical barriers, and some do not
have sidewalks. These patterns
make pedestrian and bike travel
difficult because circuitous routes
and limited access increase trip
length. Collector and arterial
streets tend to be wide to allow
vehicles to move faster and to
handle the large traffic volumes channeled to them from smaller neighborhood streets. Wide streets are
difficult and often dangerous for pedestrians and bicyclists to cross or to share with vehicles, especially if
Exhibit 4-11: Map of Chesterfield, Missouri. Neighborhood roads (in dark
blue) serve only local residents, directing all traffic to arterial streets (in
yellow) where most retail is located. Highways (in red) also serve local
travel needs, but carry large volumes of traffic at high speed.
Source: © 2013 Google
   Studies included in the review used a variety of different metrics to measure the amount people walked, some
of which were based on time spent walking and others on the number of trips.
443 Saelens and Handy 2008
444 Rodriguez, et al. 2009
445 McConville, et al. 2011

Effects of Different Types of Development on the Environment
they lack sidewalks or crosswalks. Such poor pedestrian environments discourage walking and bicycling,
leading people to rely on driving, even for short trips. Street grids with short blocks can provide multiple
routes for traffic and make walking and biking easier and safer.

Many communities created hierarchical street patterns in the belief that widening and straightening
streets, eliminating intersections, and reducing neighborhood traffic volumes by locating retail along
arterials can improve traffic safety.446 However, traffic safety studies have failed to support this belief.
For example, an analysis of the association between car crashes and urban form in the city of San
Antonio, Texas, found that locating retail and
commercial uses on arterial streets away from
residential areas and designing roads to funnel all traffic
through an area on these arterials made streets more
dangerous.447 Each additional mile of arterial street was
associated with an increase of 15 percent in the number
of car crashes and a 20 percent increase in the number
of fatal crashes; each additional large, single-use store448
was associated with a 6.6 percent increase in the
number of car crashes; and each additional arterial-
oriented retail or commercial parcel was associated with
a 1.3 percent increase in the number of car crashes.
Pedestrian-scaled retail and commercial
developments449 were associated with 2.2 percent fewer
crashes. The researchers found similar trends for the
number of crashes resulting in injuries. A later study of
the same area looked specifically at crashes involving
pedestrians and bicyclists.450 Each additional mile of
arterial street was associated with a 9.3 percent
increase in vehicle-pedestrian crashes and a 6.6 percent
increase in vehicle-cyclist crashes; each additional large,
single-use store was associated with a 8.7 percent
increase in vehicle-pedestrian crashes; and each
additional arterial-oriented retail or commercial parcel
was associated with a 3 percent increase in vehicle-
pedestrian crashes and a 1.7 percent increase in vehicle-cyclist  crashes.
Exhibit 4-12: Downtown Fredericksburg,
Virginia. Short blocks create a compact street
grid in the city's downtown retail district, making
walking easy and enjoyable.
Photo source: EPA
   Dumbaugh and Rae 2009
447 Dumbaugh and Rae 2009
448 A large, single-use store was defined as a parcel in a retail use, with a single building occupying 50,000 square
feet or more, and having a floor-area ratio of 0.4 or less. Stores of this design tend to have large surface parking
lots and attract traffic from a broad geographic area.
449 Pedestrian-scaled retail and commercial developments were defined as parcels whose retail or commercial uses
occupy buildings of 20,000 square feet or less and had floor-area ratios of 1.0 or greater.
450 Dumbaugh and Li 2010

                                             Effects of Different Types of Development on the Environment
Street connectivity affects not only traffic safety but also environmental impacts. A meta-analysis of
travel literature showed that the degree of street connectivity is associated with the amount of car use
compared to walking and transit use.451 A study of 45 of the largest U.S. metropolitan regions
considered street connectivity, as measured by a composite factor that incorporated average block
length in the urbanized portion of the metropolitan area, average block size, and the percentage of
small blocks.452 Each standard  deviation increase in connectivity was associated with a reduction of
approximately 5.5 high-ozone  days per year.These results are likely due to decreased vehicle emissions
as well as decreased heat island effect (see Section 3.5). A study of census block groups in King County,
Washington, looked  at the correlation between a  walkability index,453 VMT, and air quality.454 It found
that a 5 percent increase in walkability was associated with a 6.5 percent reduction in VMT, a
5.6 percent reduction in nitrogen oxide
emissions, and  a 5.5  percent reduction in
emissions of VOCs. Researchers analyzed
data from a 12-county region in North
Carolina and found that a 10 percent
increase in  the  number of intersections in a
neighborhood was associated  with a
4 percent reduction in daily travel
4.2.4   Community Design

When communities are designed only to
make car travel fast and easy, they can
discourage walking and biking by making it
dangerous, inconvenient, and unpleasant.
Aspects of the built environment such as the
number of off-street paths between
destinations for cyclists and walkers, the
design of streets and parking, building
orientation, and building design all
contribute to the relative appeal of that
area to pedestrians and bicyclists and to the
Exhibit 4-13: Pedestrian-friendly streetscape. Marked
crosswalks and curb extensions into the street help make
Dickson Street in downtown Fayetteville, Arkansas, safe and
enjoyable to walk on.
Photo source: EPA
   Ewing and Cervero 2010
452 Stone 2008
   The walkability index was based on the number of intersections per square kilometer, the number of residential
units divided by acres in residential use, land use mix, and retail floor-area ratio (retail building floor area divided
by retail land area). The number of intersections was given twice the weight of the other three variables.
454 Frank, et al. 2006
455 Fan and Khattak 2008

Effects of Different Types of Development on the Environment
area's general aesthetic appearance. Together, these are often referred to as "microscale" urban design
factors—small-scale elements that affect the safety, convenience, and desirability of living and working
in more compact areas and of using transit, walking, and bicycling.

Parking is one important component of community design. The amount, type, and placement of parking
determine not only how convenient it is to drive to destinations, but less obviously,  how convenient it is
to walk or bike once there. Vast areas of parking create distances between destinations that are less
practical and less appealing to traverse by foot or by bike.456 In addition, having parking space for more
cars than nearby streets are able to accommodate tends to exacerbate congestion.457 The amount of
space cities devote to parking varies considerably. An analysis of the number of parking spaces per job in
the central business district of several cities in  the United States found that values ranged from 0.06 in
New York City to 0.91 in Phoenix.458

Street design is another component of community design with important effects on travel  mode choice.
In areas that do not include adequate bicycle and  pedestrian facilities such as sidewalks, bike lanes, and
crosswalks, travel by foot or bike can be intimidating and unpleasant. By making walking more desirable
than driving, urban design factors can encourage more walking or bicycling trips, which can reduce
vehicle travel and emissions if those trips replace  vehicle trips.

Features that improve the pedestrian environment include sidewalks, clearly marked crosswalks and
walk signals, lighting, and other amenities such as shade trees, benches, and streetscapes designed with
the pedestrian in mind. Features that improve the bicycling environment include bicycle paths and lanes
on streets, bicycle parking, and clear signage for all of these. Communities with streets designed for the
safety of all  users, also known as complete streets, can facilitate walking and biking and help residents
lead healthier lifestyles.459 For example, a  review of the literature identified six studies on the
effectiveness of street and sidewalk improvements designed to increase physical activity.460 Overall, the
median increase in the  number of people walking or biking due to these improvements was 35 percent.
An analysis of the applicability of the results found diverse  geographic locations and populations are
likely to respond similarly. One study on 90 of the largest 100  U.S. cities found that those with the most
bike lanes per resident  (those in the highest quartile) had rates of bike commuting three to four times
those of cities with the fewest bike lanes (those in the lowest quartile).461 A review of literature on the
effectiveness of a wide variety of strategies used worldwide to increase bicycle use concluded that
individual interventions, such as adding bike lanes or other bike infrastructure, are likely to be more
effective when implemented as part of a comprehensive strategy—including, for example, programs
and land use planning to encourage bike use.462
   Mukhija and Shoup 2006
457 Manville and Shoup 2005
   Manville and Shoup 2005
459 Giles, etal. 2011
460 Heath, et al. 2006
461 Buehler and Pucher 2012
462 Pucher, Dill, and Handy 2010

                                             Effects of Different Types of Development on the Environment
Many communities eliminated—or
never provided—pedestrian and
bike amenities because they
believed that streets that are
relatively forgiving of driver error
are the safest. However, a review of
the literature concludes that in
areas with a lot of development,
street design elements that slow
down drivers, such as narrow lanes,
traffic-calming measures, and street
trees, actually make roads the
safest.463 For example, an evaluation
of 13 road safety measures
implemented in  New York City
between 1990 and 2008 found that
reducing the number of travel lanes,
along with adding left-turn lanes
(and sometimes bike lanes) reduced
the number of crashes at
intersections by 13 percent and
along road segments by
67 percent.464 Other measures that
reduced crashes included installing new signals (25 percent) and adding a left-turn phase to existing
signals (17 percent). Pedestrian crashes were also reduced by an all-pedestrian signal phase that stops
traffic in all directions (35 percent),  increased pedestrian crossing time (51 percent), and high-visibility
crosswalks (48 percent). This study found that curbside bus lanes actually increased the total number of
crashes,465 and adding bike lanes increased the number of bicycle crashes at intersections. However, the
bike lanes evaluated did not include special accommodations for bicyclists at intersections, and the
study did not account for the possibility that more people were bicycling after the bike lanes were
added. A review of studies that investigated the effect of bicycle-specific infrastructure on bicyclist
safety found that clearly marked bike routes and lanes cut injury or crash rates roughly in half compared
to on-road bicycling with traffic and also consistently improved injury or crash rates compared with off-
road bicycling on routes shared with walkers and other users.466
Exhibit 4-14: 9  Avenue bicycle lane in New York City. A dedicated bike
lane with separate traffic signals separates bicyclists from vehicles on city
Photo source: Kyle Gradinger/BCGP via flickr.com
   Ewing and Dumbaugh 2009
464 Chen, etal. 2013
   The city installed bus lanes to improve bus speed and attract riders, not as a safety measure. The authors
hypothesize that the unexpected safety decline from bus lanes could be due to a lack of enforcement; cars
frequently blocked the lanes and required buses to go around them. In addition, the bus lanes evaluated were not
painted as are newer bike lanes in the city to improve visibility.
466 Reynolds, et al. 2009

Effects of Different Types of Development on the Environment
Beyond affecting travel mode choice, street and parking lot design can also have direct water quality
impacts. Designers can integrate elements to store, infiltrate, and evapotranspirate water into streets,
alleys, and parking areas, helping to minimize stormwater runoff (see Section 3.3). The design elements
of green streets and green  parking include permeable pavements, vegetated swales, planters, and
trees.467 (See Section 4.2.7  for discussion of other site-scale techniques to manage stormwater runoff.)
An evaluation of the performance of four commercially available permeable pavement systems after six
years of use found that they infiltrated essentially all precipitation during the three-month study period
in Renton, Washington, outside of Seattle.468 The quality of the water that  moved through the
permeable pavement was betterthan that of the runoff leaving an asphalt parking area. Both copper
and zinc concentrations were below toxic levels and usually below detectable levels in all infiltrated
stormwater, while asphalt  runoff consistently contained copper and zinc at toxic concentrations.
Another study of permeable pavements in North Carolina found that they can reduce and sometimes
even eliminate stormwater runoff.469 Of two sites monitored for water quality, only one had any
discharge during the study period. Its discharge of total nitrogen, total phosphorus, ammonia, and zinc
was lower than from  adjacent asphalt lots.

4.2.5  Destination Accessibility

The form of our built environment also determines how accessible different places are to each other on
a regional level. While compact development, a mix of land uses, and good community design are
important factors at a local level, researchers have attempted to define indicators of overall destination
accessibility (how easy it is to access attractions across the region) that are not directly captured by
these other metrics.

A meta-analysis of travel literature available at the end of 2009 found that destination accessibility is the
measure of the built environment that is most strongly associated with VMT and the amount people
walk.470 The authors suggest that these results show any centrally located development is likely to
generate less car traffic than  a remotely located development even if the remote development is
compact, mixed-use,  and designed for pedestrian travel.

Researchers have also studied how neighborhood accessibility influences travel behavior. Neighborhood
accessibility refers to the ease of traveling within and  between neighborhoods by a variety of options,
including car, transit, walking, and biking. It is based on  measures of population density, land use mix,
and average block size. A study measured how the travel behavior of 430 households changed when
they moved between locations with different levels of neighborhood accessibility.471 It found that
households relocating to areas with higher neighborhood  accessibility reduced their VMT, person miles
   EPA, What is Green Infrastructure? n.d.
468 Brattebo and Booth 2003
469 Bean, Hunt, and Bidelspach 2007
   Ewing and Cervero 2010
471 Krizek 2003

                                            Effects of Different Types of Development on the Environment
traveled, and the number of destinations per trip while simultaneously increasing the number of trips

Another study considered the factor of urban contiguity and its relationship to air pollution levels.472
Contiguity measures the patchiness in a developed area, or how much development occurs isolated
from other developed areas.473 Satellite measurements of nitrogen dioxide levels in 83 cities found that
urban contiguity is associated with lower levels of nitrogen dioxide. Specifically, a decrease in contiguity
of one standard deviation is associated with a 31 percent increase in  nitrogen dioxide levels. While
population size was the single most important predictor of nitrogen dioxide levels in a city, results
showed that nitrogen dioxide increases caused by a 10 percent increase in population could be offset by
a 4 percent increase in  urban contiguity.

Finally, one study showed that air quality is also related to population centrality, a measure of how a
population is distributed relative to a central business district. The study found that while population
density was associated with higher population-weighted levels of PM2.5 and aggregate pollutant levels,
population centrality was associated with lower population-weighted levels of these measures as well as
ozone.474 The authors speculate that these findings could be explained in part by how travel patterns are
influenced by population centrality and by how air pollution varies across a geographic area. Ozone
concentrations tend to peak at some distance from an urban center,  so as populations are more
dispersed, more people are located in this  zone of highest concentration.475

4.2.6  Transit Availability

In addition to locating development near transit stations, how we build and manage transit and related
infrastructure determines how useful and convenient public transit is, which in turn influences how
much people choose to use it. Transit access can be improved not only by how we build communities
surrounding transit, but also by expanding the supply of transit itself through construction or service
improvements (Exhibit 4-15). For example, among a set of residents surveyed before and after a new
light-rail stop opened in a Salt Lake City neighborhood, ridership increased from 50 to 69 percent.476
Service improvements that can improve ridership include increasing frequency, particularly on  routes
with infrequent service; making service more reliable; having easy-to-remember departure times and
readily available schedules; expanding routes, particularly to unserved or poorly served areas; adding
new buses; and lowering fares.477'478 Researchers developed a model to study the factors affecting the
472 Bechle, Millet, and Marshall 2011
473 Contiguity is calculated as the ratio of the main contiguous built-up area to the total built-up area of a city. It is
not correlated with compactness, calculated as the ratio of built-up area to total buildable area within a circle
surrounding the main built-up area of a city.
   Population centrality is not correlated with population density.
475 Clark, Millet, and Marshall 2011
476 Brown and Werner 2007
477 Evans 2004
478 Pratt and Evans 2004

Effects of Different Types of Development on the Environment
                                      Exhibit 4-15: Streetcar in San Francisco. The F Market & Wharves line
                                      operates 20 hours a day, 365 days a year, connecting destinations popular
                                      with both commuters and tourists. Service runs at least every 15 minutes
                                      and as frequently as every 6 minutes.
                                      Photo source: EPA
widely varying levels of transit
ridership across U.S. cities.479 They
found that four types of factors can
explain most of the variation:

    •  Regional geography (i.e.,
       total population,
       population density,
       geographic land area, and
       regional location).
    •  Median household
    •  Population characteristics
       (i.e., political party
       affiliation and percentage
       of households without a
    •  The number of trips taken
       using neither transit nor a personal vehicle (e.g., walking, biking, or carpooling).

While these types  of regional characteristics are most influential in determining levels of transit use,
transit policies are important as well. This study found that more frequent service and lower fares can at
least double transit use in a given area.

The effects of increased transit service on VMT are less clear. A study of 228 U.S. metropolitan areas
found that the number of buses and train cars in a region does not influence VMT.480 However, models
have shown that modest effects are possible; transit service  improvements  can reduce VMT by up to
1 percent during the first 10 years after investment and up to 2 percent thereafter.481 In Portland,
Oregon, neighborhoods with more public transit (more bus stops and/or shorter distances from homes
to light rail stations) have fewer people who commute by driving alone.482 Data on air pollution support
these findings. One study found that the  availability of transit is associated with lower population-
weighted  concentrations of PM2.5.483

Irrespective of its effect on VMT, transit availability can also improve users'  health. Transit users who
walk to their transit stop spend on average 24 minutes per day walking for travel, and 29 percent of
these transit users meet the U.S. surgeon general's recommendation of at least 30 minutes  of physical
  Taylor, et al. 2009
  3 Duranton and Turner 2011
  1 Rodier 2009
  ' Clark, Millet, and Marshall 2011

                                            Effects of Different Types of Development on the Environment
activity per day by walking to and from transit.484 A study of Charlotte, North Carolina, residents before
and after construction of the city's light rail system found that daily use of the system was associated
with a reduction in body mass index485 and an 81 percent reduction in the likelihood of becoming obese
over a 12-to 18-month period.486

4.2.7  Green Building

How we build our communities involves not just the layout of streets and buildings, but also the
materials and approaches we use to construct the buildings. The term green building refers to the
practice of using resources efficiently and  reducing impacts on human health and the environment in all
phases of a building's lifecycle: pre-design, siting, design, construction, operations, maintenance,
renovation, and demolition. Many of the decisions that developers make during the pre-design and
siting phases have already been covered in other sections. For example, the location of a home helps
determine how far people travel to commute to work, get to school, shop, and participate in
recreational activities, as well as whether they travel by car, public transit, walking, or biking. The travel
behavior of a building's occupants is an important component of a building's overall energy use, and
part of making a building energy efficient is siting the building in a central location near businesses,
schools, recreational options, and transportation options.

Although part of building green involves carefully choosing the site location, this section discusses other
aspects of green building:

    •  Ensuring that building construction and renovation practices limit environmental impacts.
    •  Conserving energy and water in building operations.
    •  Using building materials that are environmentally safe for occupants.
    •  Designing sites to allow the capture and reuse or infiltration of stormwater.

These broad categories include just some of the wide range of techniques and strategies encompassed
by green building approaches. This section discusses these approaches to provide  a general sense of
how green building could protect the environment and human health. Unlike approaches to how we
build our communities, the most environmentally preferable products for constructing and operating
buildings might vary depending on location and are likely to change as more performance data are
collected and new products come on the market. In addition, rather than simply adopting individual
practices from  a menu, the most successful green building projects use an integrated, interdisciplinary
approach that considers how individual components will interact with each other and with the chosen
site. Teams including architects, construction contractors, operations staff, and building occupants
collaborate to plan integrated systems and optimize performance after building construction.
484 Besser and Dannenberg 2005. Median walking time was 19 minutes.
485 Body mass index for light rail users compared to comparable non-users declined by 1.18 kilograms per meter
squared, or 6.45 pounds for a person who is 5 feet, 5 inches.
486 MacDonald, et al. 2010

Effects of Different Types of Development on the Environment
  Exhibit 4-16: Tupelo Alley apartments in Portland, Oregon. This building
  was awarded a gold certification by Leadership in Energy and
  Environmental Design (LEED) for its water and energy efficiency and the use
  of low-emitting materials inside to provide better indoor air quality. It is
  also within walking distance of neighborhood amenities and an easy
  commute by bike or transit to downtown.
  Photo source: EPA
The National Academy of Sciences
estimated in 2009 that 57 million
new housing units would be
needed by 2030 to accommodate
projected population growth.487
This estimate does not include
additional buildings needed for
commercial  and industrial uses.
The choices  we make about how to
construct these buildings will be
important determinants of the
ecological and human health
impacts of our built environment.
In addition,  many green building
techniques are applicable to
building retrofits and renovations,
so the potential for better
environmental performance from
the building sector is large indeed.
Construction/Renovation Practices
Green building techniques involve a wide range of construction practices designed to minimize the
environmental and health impacts of construction. Advances in construction technology and research
evaluating impacts of different options will change our understanding of best practices. This section
presents a sample of green building construction practices to illustrate the issues they can address.

One green building strategy is using locally or regionally sourced construction materials to shorten the
distance between the suppliers and construction sites, thereby reducing transportation emissions. Other
strategies include limiting sediment and nutrient releases from construction sites, preventing soil
erosion, limiting the amount of land disturbed, designing buildings to facilitate their deconstruction at
the end of their useful life, and using energy and water more efficiently during construction.488 For
example, diesel engines in construction vehicles such as backhoes, bulldozers, excavators, and loaders
emit air pollution, including NOX, particulate matter, hydrocarbons, and carbon monoxide.489 Several
strategies can reduce construction vehicle emissions, including reducing idling time, improving
maintenance, purchasing energy-efficient models, and using technological controls to reduce
   National Research Council of the National Academies, Driving and the Built Environment 2009
  !Shen, etal. 2007
  ' Lewis, et al. 2009
  ' Lewis, et al. 2009

                                             Effects of Different Types of Development on the Environment
Radon-resistant construction techniques for mitigating radon exposure can involve both passive
methods, such as improving ventilation to the outside or sealing radon entry points, and active methods
such as sub-slab depressurization, which draws radon out of the sub-soil to the outside air. The best
method will depend on building type, soil conditions, and climate, but radon reductions of up to
90 percent are possible.491

Energy Efficiency
Green  building strategies can improve the environmental performance of buildings by making them
more energy efficient. Homes built between 2000 and 2005 were 14 percent more energy efficient per
square foot than homes built in the 1980s and 40 percent more energy efficient than homes built before
1950.492 More stringent residential building energy efficiency codes and standards are partly responsible
for this improvement.493 However, through various green building techniques and strategies, a building's
energy efficiency can well exceed that
required by building codes, and the
potential to improve the energy
consumption of the building sector (see
Section 2.2.2) through both new
construction and renovation is significant.
A review of retrofits of commercial
buildings found energy savings of 50 to
70 percent around the world.494 For
example, converting the heating systems
in  10 schools from low-pressure steam
systems to low-temperature hot water
systems reduced heating energy use by
an average of two-thirds.495

Many different techniques and strategies
can help improve the energy efficiency of

    •    Insulation—Effective insulation
       and good windows create a
        barrier between indoor and
       outdoor air, limiting heat loss or gain, depending on the season. In areas with cold climates,
        houses built to maximize the thermal barrier between indoor and outdoor air use only 10 to
Exhibit 4-17: Cherokee Mixed-Use Lofts in Hollywood, California.
This residential and retail building is 40 percent more efficient than
required by California's building code; has a green roof, water-
efficient fixtures, drought-tolerant landscaping, and solar heating;
and uses materials throughout that are recycled and contain low or
no VOCs. It is close to shops, services, and other amenities so
residents can walk for many daily needs.
Photo source: Calderoliver via Wikipedia Commons
   Rahman and Tracy 2009
   U.S. Department of Energy 2012
   The 2006 International Energy Conservation Code requires buildings to be 14 percent more energy efficient
than the original code in 1975.
494 Harvey 2009
495 Durkin 2006

Effects of Different Types of Development on the Environment
       25 percent of the energy of a house built to minimum code standards.496 Energy-saving
       strategies can also reduce the amount needed for cooling by more than 50 percent. In areas
       with cool evenings, allowing adequate nighttime ventilation can often eliminate the need for air
       conditioning entirely.497 As the climate warms and extreme heat events increase, better-
       insulated homes can help people avoid heat-related illnesses and  death by reducing the amount
       of energy they need to use to keep their home at a safe temperature.

       While improving the thermal performance of buildings, green building practices also aim to
       control the amount of indoor air moisture to prevent the growth of mold and avoid allergic and
       respiratory effects (discussed in Section 3.4.4). Controlling both insulation and air leakage is
       critical for achieving an appropriate moisture balance,  particularly for retrofits of older homes
       where it can be more difficult.498

       Heating and cooling systems, appliances, and lighting—An optimal heating, ventilation, and air
       conditioning (HVAC) system can reduce energy use by 30 to 75 percent, in addition to any
       savings achieved by other techniques.499 EPA and the U.S. Department of Energy created the
       voluntary ENERGY STAR program in 1992 to help consumers and businesses identify the most
       energy-efficient products, homes, buildings, and practices.500 An evaluation of the impacts of the
       program found that from 1992 through 2006, the use of ENERGY STAR-labeled products,
       including office equipment, consumer electronics, residential HVAC systems, lighting, and
       appliances, saved 4.8 exajoules (1018 joules) of energy and avoided 82 teragrams of carbon
       dioxide equivalent.501 This savings represents about 1.5 percent of the 311 exajoules consumed
       by the entire residential sector between 1992 and 2006 (see Exhibit 2-11). The savings came
       primarily from computer equipment, residential light fixtures, televisions, and furnaces. The
       same study projected that between 2007 and 2015, ENERGY STAR-labeled products would save
       12.8 exajoules of energy and avoid 203 teragrams of carbon dioxide equivalent.502

       Energy-efficient lighting involves not only using better technology, but also minimizing the need
       for artificial lighting through daylighting techniques. Incorporating skylights, solar tubes, and
       north-facing windows into the building design, as well as positioning spaces and furniture to
       maximize sunlight that enters the structure, can illuminate the interior space without consuming
       electricity.503 Minimizing artificial lighting also reduces  excess heat from light bulbs, which in
       turn lowers the energy demand for air conditioning. For example, in perimeter offices,
496 Harvey 2009
497 Harvey 2009
498 Lubeck and Conlin 2010
499 Harvey 2009
500 EPA, About Energy Star n.d.
501 Sanchez, et al. 2008
502 Sanchez, etal. 2008
503 U.S. Department of Energy 2002

                                             Effects of Different Types of Development on the Environment
        daylighting can reduce energy used for lighting by 40 to 80 percent and energy used for lighting
        and cooling together by 20 to 33 percent.504
        Passive strategies—Passive
        strategies involve modifying
        key design elements,
        including building size,
        orientation, the height-to-
        floor area ratio, and the
        wall-to-window area ratio.
        In general, the larger the
        building is, the more energy
        needed for heating and
        cooling.  For example,
        researchers estimate that if
        1 percent of U.S. households
        lived in a 2,000-square-foot
        single-family house rather
        than one that is 2,400
        square feet, the United
        States would save 3,164
        billion Btu  annually.505
        Savings are more significant
        when comparing single-family homes to homes in multi-unit buildings because of the
        efficiencies gained by shared walls, ceilings, and floors. If 1 percent of households lived in a
        2,400-square-foot apartment rather than a single-family home of the same size, researchers
        estimate 27,906 billion Btu could be saved annually. Other passive strategies include using
        natural ventilation to reduce the energy needed for cooling and orienting buildings on a site to
        take advantage of the optimal position relative to the sun, wind direction, and topography.
Exhibit 4-18: Sustainably designed kitchen. This kitchen in Eagle Rock,
California, uses natural lighting to reduce the need for electricity.
Rolling wood screens can be moved to shade the south-facing
windows during hot weather, and a tree grows through the outdoor
deck to provide additional shade. Sustainable materials were used in
the construction, including countertops made with recycled coal fly
Photo source: Jeremy Levine Design via flickr.com
These approaches are just some of the energy-saving strategies and technologies for green building
design and operations. A review of the literature shows that using combinations of available options
could reduce annual energy use per unit of floor area by a factor of three to four for new buildings and
two to three for existing buildings.506

Water Conservation
Green  building strategies can increase the environmental performance of buildings by using water more
efficiently. Not only does reducing water consumption conserve a valuable resource, it reduces the
energy needed to pump water from a water treatment plant to homes, to heat the water (in some
   Harvey 2009
   Kockelman, etal.2009
   Harvey 2009

Effects of Different Types of Development on the Environment
cases), to pump it back to a wastewater treatment plant, and finally, to treat it before discharging it back
to the environment.

Water-efficient household appliances and fixtures can yield significant water savings. For appliances
using hot water, energy savings can also be substantial. An assessment of standard versus efficient
clothes washers, toilets, and showerheads, found that efficient models used 38 to 58 percent less water,
consume 28 to 35 percent less energy, and emit 28 to 52 percent fewer greenhouse gases over their
entire lifecycle, including manufacture, use, and end-of-life disposal.507 In a similar study, researchers
analyzed the potential reductions of water use, energy use, and greenhouse gas emissions from using
available water-efficient clothes washers, dishwashers, faucets, and showerheads. They found that in
Australian households, up to 10.2 kiloliters (2,695 gallons) of water and 965 kilowatt hours of energy per
person per year could be saved, amounting to a 30 percent reduction in water use and a 60 percent
reduction in energy use from these household appliances and fixtures.508

Outdoor water use accounts for 31 percent of total water use for single-family households on average,
but can be higher in arid climates (see Exhibit 2-16). Smaller lots with less turf or landscaped area  need
less water, and water-efficient landscaping and irrigation technology can significantly reduce water use.
For example, drip irrigation delivers water only as fast as the soil is able to absorb it and limits surface
water runoff and evaporation that often occurs with conventional sprinkler systems. Landscaping with
native  plants adapted to the natural rainfall patterns instead of using turf grass can also reduce water
needs. In the arid  western United States, estimates for how much changes  in landscaping and irrigation
practices could save range from 35 to 70 percent of per capita water use.509 A study in Florida, where
irrigation accounts for 64  percent of residential water use, found that changes in irrigation timing could
reduce water use  by 30 percent. When combined with replacing approximately half of the turf grass
area with native plants, savings could reach 50 percent.510

Office and other types of commercial and institutional buildings such as hospitals, hotels, and schools
can also achieve significant water savings  using these and other techniques. Strategies for commercial
and institutional facilities  include developing a water management plan for each facility, regularly
checking for and repairing leaks, using the most water-efficient  bathroom fixtures, and optimizing
cooling systems, including determining if they can provide or use on-site sources of water.511

EPA recognizes through its WaterSense labeling program512 products that are at least 20 percent more
efficient and perform as well or better than comparable  products. The program also provides national
specifications for water-efficient new homes and recognizes professional certification  programs for
landscape irrigation professionals that have verified proficiency in water-efficient irrigation system
design, installation and maintenance, and auditing.
507 Lee and Tansel 2012
508 Beal, Bertone, and Stewart 2012
509 Hurd 2006
510 Haley, Dukes, and Miller 2007
511 EPA, WaterSense at Work 2012
512 EPA, WaterSense n.d.

                                            Effects of Different Types of Development on the Environment
Materials Selection
Careful selection of construction materials helps conserve natural resources and protect the
environment. The building sector accounts for 24 percent of global natural resource extractions.513 Using
recycled, refurbished, and/or salvaged materials such as metal, glass, timber, brick, cement, and steel
reduces the demand for raw materials; minimizes the amount of waste that needs to be disposed of;
and reduces energy, chemical, and water use in manufacturing. Sturdy materials like concrete and steel,
for instance, are energy-intensive to produce, so much  so that the structural frame of a typical office
building can account for 15 percent of its lifetime energy use.514 A study of construction and demolition
waste generation in Florida estimated that as much as 91 percent of building-related construction and
demolition waste can  be recycled with current technology, far more than the estimated 9 percent of
construction and demolition waste that is actually recycled in the state.515

A lifecycle assessment that considered the energy footprints, water footprints, and contributions to
global warming of different building materials found that they vary considerably.516 For example, the
study found that for exterior paving, clay tiles require 85 percent less energy and produce 66 percent
fewer greenhouse gas emissions than ceramic tiles. For insulation, rock wool has an energy footprint
four times lower and  a water footprint 8.4 times lower and emits 4.7 times fewer greenhouse gases
than polystyrene tiles and  rigid polyurethane foam.

The materials selected for  building construction affect indoor air quality. As discussed in Section 3.4,
many of the materials that we use to build our homes and offices emit chemicals with known or
potential adverse health impacts. Green building strategies seek to minimize or eliminate these
materials. For example, researchers measured the total amount of several  VOCs for several conventional
and green materials.517 All  of the green materials emitted far fewer VOCs than their conventional
counterparts, as shown in  Exhibit 4-19.
Green Material
Trex518 decking wood
Ceramic floor tile
Water-based paint

Total VOCs Emitted in 5 days (mg/m2)

Conventional Material
Pressure-treated wood
Vinyl floor tile
Oil-based paint
Wood stain
Total VOCs Emitted in 5 days (mg/m2)
    Exhibit 4-19: Total VOCs (in milligrams per square meter) emitted over a five-day period from green materials
    compared to conventional materials.
    Source: James and Yang 2004

The materials selected for use inside buildings are also important for indoor air quality. EPA's Design for
the Environment Program helps households, businesses, and institutions select cleaners and other
513 Bribian, Capilla, and Uson 2011
514 Horvath 2004
515 Cochran, et al. 2007
516 Bribian, Capilla, and Uson 2011
517 James and Yang 2004
   Trex° is a wood alternative made of reclaimed and recycled wood and plastic fibers. This document does not
convey official EPA approval, endorsement, or recommendation of this product.

Effects of Different Types of Development on the Environment
products that are safer for the environment.519 The program is based on a methodology for comparing
the environmental and human health effects of chemical alternatives to minimize risk.520

A review of strategies to mitigate indoor air pollution exposures found that portable air cleaners can
help reduce exposure to small airborne particles.521 However, they are not proven effective for removing
larger airborne particles (including many allergens) or VOCs, highlighting the importance of removing
pollutant sources and ventilating indoor spaces with clean, outdoor air. Nevertheless, few scientific
studies have evaluated the health benefits of avoiding products containing VOCs.

Site-Scale Green Infrastructure
Green infrastructure at the site scale, also known as low-impact development, is a strategy for managing
stormwater where it falls, allowing soils and vegetation to absorb and filter the water, which reduces
many of development's impacts on water quality that are discussed in Section 3.2. Examples of green
infrastructure techniques include:

    •  Infiltration techniques, such as permeable pavements, disconnected downspouts, and rain
       gardens (Exhibit 4-20)—They are engineered structures or landscape features designed to
       capture and infiltrate stormwater, reduce runoff volume, and treat or clean runoff.

    •  Evapotranspiration practices, such  as green roofs, bioswales, trees, and other vegetation—They
       can reduce stormwater runoff volumes by returning water to the atmosphere through
       evaporation of surface water or through transpiration from plant leaves. Trees and shrubs can
       also filter air pollutants and improve air quality.522

    •  Capture and reuse practices, such as rain barrels and cisterns—They capture stormwater for
       non-potable household uses, irrigation, or gradual  infiltration.

Estimates of the performance of any given practice vary considerably because of wide  variation in how
and where green infrastructure is installed. For example, estimates for the runoff reduction from green
roofs are between 50 and 100 percent, depending on the roof characteristics and annual precipitation
patterns.523 Researchers have consistently found potential  building energy savings524 and air pollution
and carbon dioxide reductions525 from green roofs, but precise values vary. Other environmental
benefits of green roofs include the ability to neutralize acid rain, attract wildlife, and mitigate the heat
island effect.526 A review of the literature on the performance of individual green infrastructure practices
found that bioretention areas, permeable pavements, and  green roofs can reduce runoff volumes and
519 EPA, Design for the Environment n.d.
520 Lavoie, et al. 2010
521Sandel, etal. 2010
522 Nowak and Greenfield 2012
523 Rowe 2011
524 Sailor, Elley, and Gibson 2012
525 Rowe 2011
526 U.S. General Services Administration 2011

                                          Effects of Different Types of Development on the Environment
Exhibit 4-20: Citygarden in St. Louis. Covering two city
blocks in downtown St. Louis, Citygarden includes six
rain gardens covering 5,000 square feet that capture
stormwater runoff from the park and adjacent streets.
Photo source: EPA
                                                the concentration of many pollutants, including
                                                copper, lead, and zinc.527 In 2009, the National
                                                Research Council reviewed recent studies on the
                                                performance of various bioretention techniques.528
                                                Runoff volume reductions ranged from 20 to
                                                99 percent, with a median  reduction of about
                                                75 percent. The report concluded that practices
                                                that harvest, infiltrate, and evapotranspirate
                                                stormwater are important tools for reducing
                                                pollutant loadings from smaller storms. These
                                                smaller storms tend to carry away the bulk of the
                                                pollution on roads and parking lots. However, as a
                                                first line of defense, non-structural practices such as
                                                better designing building sites, disconnecting gutter
                                                downspouts, and conserving natural areas
                                                dramatically reduce runoff volumes and pollutant
                                                loadings resulting from development.

                                                The benefits of green infrastructure are not just
                                                ecological. Green infrastructure can also make an
                                                area more attractive for residents and visitors and
                                                increase recreation space.  In addition, a review of
                                                literature on the effect of green infrastructure  on
                                                human health found that epidemiological,
                                                experimental, and survey data suggest that there is
considerable potential for green infrastructure to improve the health and well-being of urban residents,
likely due to physiological, emotional, and cognitive changes.529

4.3    Scenario Planning

Many of the patterns and practices discussed in this report—locating new development away from
sensitive areas and on previously developed sites near transit; building compact, mixed-use
communities; designing communities to serve bicyclists and pedestrians as well as cars; and using green
building approaches—have demonstrated environmental benefits. Through these strategies, we can
reduce land and habitat consumption, reduce the energy and resources needed for new infrastructure,
and reduce growth in vehicle travel along with its associated human health and environmental impacts.
 Dietz 2007
 National Research Council of the National Academies, Urban Stormwater Management in the U.S. 2009
'Tzoulas, etal. 2007

Effects of Different Types of Development on the Environment
As shown in Section 4.2, the efficacy of any one of these practices depends in large part on its context.
The benefits of increasing housing or employment density, for example, depend on whether the density
occurs along with a variety of easily accessible shops and services for residents and employees, whether
streets are designed to make walking and biking between destinations convenient and safe, whether the
development occurs near a central business district, and whether the buildings are designed to use
energy and water efficiently. Using these strategies together enhances the benefits they bring

This section considers several examples of scenario planning studies that look at how the combined
effects of such land use strategies could improve the environmental outcomes of development. Scenario
planning is the process of considering a range of plausible trends and evaluating the future outcomes
that would likely result from each.530 Scenarios are not forecasts or predictions of what will happen.
They are intended to provide information for communities to understand how different land use
decisions could lead to different outcomes based on assumptions about future development trends.
Communities typically use scenarios to highlight key considerations for long-range planning or to
understand the long-term impacts of short-term decisions. When a collaborative public process informs
scenario planning and the modeling is based on locally important values, the results can help community
leaders make broadly supported planning and development decisions.

Many regions have conducted scenario-planning exercises to help understand the anticipated impacts of
land use decisions on the environment and human health. A 2007 review covered  80 scenario-planning
exercises from more than 50 metropolitan regions.531  For example,  researchers developed four land use
scenarios for a study of an area  of southern California  that includes north and west San Diego County
and parts of Riverside and Orange counties.  Each scenario had two variants: a population increase of
500,000 and a population increase of 1,000,000.

   •   The Coastal Future scenario concentrated residential development in high-density areas near
       the coast, away from rural areas.
   •   The Northern Future scenario concentrated new, low-density housing in suburban and rural
        areas of the northern part of the study area.
   •   The Regional Low-Density Future scenario spread large-lot development throughout the study
   •   The Three-Centers Future concentrated residential development near existing cities.

Modeling showed that the Three-Centers Future resulted in the best air quality outcomes for the region,
while the Regional Low-Density Future resulted in the  largest increase in VMT and the  highest levels of
air pollution.532
530 Mahmoud, et al. 2009
531 Bartholomew 2007
532 Kahyaoglu-Koracin, et al. 2009

                                           Effects of Different Types of Development on the Environment
Long-term growth patterns in the eight counties of the San Joaquin Valley in California were also the
subject of a modeling study that included:

    •   A baseline growth scenario that assumed no change in development trends for residential
    •   A controlled growth scenario that assumed road capacity would not increase, alternative forms
       of transportation would be expanded, and new residential growth would be high density.
    •   An uncontrolled growth scenario that assumed increases in road capacity, no expansion of
       alternative forms of transportation, and low- and very low-density new residential growth.
    •   An as planned scenario that assumed current plans—increases in road capacity, new high-speed
       rail, and no change in development trends for residential density—would  be implemented.

The model projected that, regionwide, the controlled growth scenario would result in a 6 to 10 percent
reduction in total emissions compared to the baseline growth scenario, while the  unplanned growth
scenario would result in a 7 to 10 percent increase in total emissions over the baseline growth scenario.
Projections for reductions in VMT and vehicle emissions were the highest for areas that were relatively
the densest at baseline.533

Another study assessed  projected 2050 pollutant emissions across 11 major metropolitan regions in the
Midwestern United States.534 The study evaluated a business-as-usual scenario and a compact growth
scenario, the latter of which was  based on changes in the relative proportion of the population in urban,
suburban, and rural census tracts between 1980 and 2000 in Portland, Oregon, a region that
implemented several growth  management policies over this time. The model projected VMT across all
metropolitan areas to be 6.0 percent lower by 2050 under the compact growth scenario than under the
business-as-usual scenario. Projections for vehicle pollutants took into account different travel speeds
and frequencies of vehicle starts  in  urban, suburban, and rural areas. The model projected reductions of
6.0 percent for PM2.s, 5.6 percent for NOX, 5.6 percent for carbon monoxide, 5.3 percent for VOCs, and
5.1 percent for carbon dioxide under the compact growth scenario compared to the business-as-usual

A similar study of the same 11 major Midwestern metropolitan regions evaluated  how development
decisions could influence air quality changes projected to occur between 2000 and 2050.53S Increased
density was associated with a lower rate of VMT growth, although effects were  more pronounced when
density was increased in urban versus suburban areas. Overall, the model predicted VMT would increase
64 percent under the business-as-usual scenario and 56 percent and 47 percent under two different
smart growth scenarios. The rate of growth in carbon dioxide emissions showed the same relative
trends: 23 percent under the  business-as-usual scenario and 17 percent and 15 percent under two
different smart growth scenarios. Growth in  carbon dioxide emissions was much lower than the VMT
growth under all scenarios due to anticipated improvements in vehicle emissions technology. Put
533 Niemeier, Bai, and Handy 2011
534 Stone, Mednick, et al. 2007
535 Stone, Mednick, et al. 2009

Effects of Different Types of Development on the Environment
another way, under the smart growth scenarios, each 10 percent increase in population density was
associated with a 3.4 percent reduction in the household VMT growth rate and a 3.0 percent reduction
in the carbon dioxide emission growth rate.

The National Research Council published results of a national modeling exercise for different
development scenarios:

    •   One scenario assumed that, beginning in 2000, 75 percent of all new homes would be built in
       more compact developments, with residents driving 25 percent less.
    •   A more moderate scenario assumed that 25 percent of new homes would be built in more
       compact developments, with residents driving 12 percent less.
    •   A base-case scenario assumed that all new homes would be built at the average density of
       homes built during the 1990s.

The committee estimated that by 2030, VMT, associated fuel use, and carbon dioxide emissions would
be reduced below the base case by 7 to 8 percent for the first scenario and by about 1 percent for the
second scenario. By 2050, reductions would be 8 to 11 percent and 1.3 to 1.7 percent, respectively.536
The report noted that both scenarios are based on numerous assumptions that represent departures
from current trends, and the authoring committee members disagreed about how realistic these
assumptions are for the United  States.

In another national modeling exercise, researchers evaluated five scenarios based on different levels of
population density from 2005 to 2054: three in which population density declined by 47 percent,
39 percent, and 13 percent; one in which population density remained constant; and one in which
population density increased 11 percent.537 Under the scenario of increased population density, vehicle-
related carbon dioxide emissions were projected to decline by 5 percent over 50 years compared to the
scenario of no change in population density. Emissions were projected to increase by 15, 70, and
95 percent under the scenarios of population density decreasing 13, 39, and 47 percent, respectively.

In an attempt to summarize the voluminous literature available on scenario planning, researchers
conducted a meta-analysis of scenarios that considered the impact of land use decisions on
transportation.538 The results suggest that increasing average regional density by 50 percent, directing
development to infill locations,  mixing land uses, and coordinating transportation investments could
reduce VMT 17 percent below current trends between 2007 and 2050.
536 National Research Council of the National Academies, Driving and the Built Environment 2009
537 Marshall 2008. Values were chosen based on data showing average urban population density declined by
13 percent from 1960 to 1990 and by 34 percent from 1990 to 2000.
538 Bartholomew and Ewing 2008

                                          Effects of Different Types of Development on the Environment
4.4    Summary

Research has shown that development decisions have both direct and indirect effects on the
environment and that growth can be accommodated in ways that better protect the environment and
human health. Strategies that minimize negative environmental impacts include modifying where we
build to direct development away from sensitive natural areas and onto infill, brownfield, and greyfield
sites while locating jobs, homes, and services near transit. Strategies also include modifying how we
build to focus on more compact, mixed-use development that uses green building techniques and makes
walking and biking convenient and enjoyable.

Used in combination, these practices can significantly reduce impacts to habitat, ecosystems, and
watersheds and can reduce vehicle travel and energy use, which in turn reduces emissions that cause
local, regional, and global air quality concerns.

Chapter 5. Conclusion
Across the country, communities are concerned about the built environment not just for quality of life
and economic reasons, but also because of the effect that development has on human health,
environmental resources, and natural habitats. Our Built and Natural Environments reviews the scientific
literature and demonstrates that the built environment can significantly affect ecological and human
health. As residents and public officials have come to understand the relationships among land use,
transportation, and the environment, they have begun to seek new ways to grow—ways that benefit
the environment and that support the jobs, economic development, health, and quality of life that
depend on the protection of air and water quality.

How and where we build affects the natural environment and human health in the following ways:

    •  Habitat and Ecosystems—Development uses land and modifies habitats and ecosystems.  In
       many metropolitan areas, the pace of land development continues to far exceed the pace of
       population growth. Not only does development directly destroy areas of natural habitat, it can
       fragment habitat and lead to the invasion of non-native species that severely alter ecosystem
       function and reduce biodiversity. Development that reuses and repurposes already-developed
       land takes development pressure off sensitive and critical habitats such as wetlands and forests.
       It can preserve ecosystem integrity and create amenities for adjacent neighborhoods.

    •  Water Quality—Development affects water quality by changing the natural flow of water in a
       watershed, particularly by increasing impervious surfaces and channeling stormwater runoff. At
       least 850,000 acres of lakes, reservoirs, and ponds and 50,000 miles of rivers and streams are
       impaired by stormwater runoff. As communities nationwide strive to protect their water
       resources, both for natural habitat and for clean drinking water, understanding the impact of
       development on water quality is important. Impervious surfaces increase runoff volumes and
       speed, which change the physical form of our stream systems and increase pollution in our
       waterways. Water quality can be improved by minimizing impervious surfaces through more
       compact, mixed-use development and using green infrastructure to manage stormwater where
       it falls.

    •  Air Quality—Air quality is related to  how and where we build because building practices affect
       indoor air  pollution levels and the energy needed to power buildings, and development patterns
       affect travel behavior. Gasoline-powered vehicles are significant contributors to air pollution.
       Although technology has significantly reduced per car vehicle emissions, the approximate
       250 percent increase in VMT since 1970 has offset potential  gains. There is significant evidence
       that compact, mixed-use development focused around transit can reduce vehicle travel and air
       pollution from motor vehicles. Infill development, including redevelopment of brownfields,
       often provides better access to transit services, which would reduce vehicle travel compared
       with development on the edge of the metropolitan area. In addition, designing roads to

       accommodate walkers and bikers safely and comfortably can encourage people to travel short
       distances without a car.

    •   Global Climate—Like air quality, global climate is affected by how and where we build because
       those decisions influence the energy needed to build and operate buildings and the amount
       people travel. Combustion of motor vehicle fuel emits carbon dioxide, a greenhouse gas that
       helps trap heat in the atmosphere, and transportation is responsible for 27 percent of U.S.
       greenhouse gas emissions. Residential and commercial buildings are responsible for 18 and
       17 percent, respectively. Many communities understand that global warming is a serious threat
       and are encouraging practices that reduce greenhouse gas emissions. Examples include
       providing more transportation choices, reducing the need to travel by car, and  improving the
       energy efficiency of buildings.

    •   Contamination and Risk in Communities—Old abandoned land in urbanized areas, potentially
       contaminated with hazardous or toxic waste, poses risks to communities. Redeveloping
       brownfields and hazardous waste sites provides the opportunity to clean  up contaminated sites,
       reducing threats to water quality and human health. Brownfield and hazardous waste site
       redevelopment also uses existing infrastructure, including roads and water and wastewater
       systems, more efficiently, and it protects open space by placing new development in previously
       developed areas rather than in undisturbed habitat.

    •   Public Health—Where and how we build our communities affects not only the  amount of
       pollution people are exposed to, but also how likely they are to get adequate physical exercise,
       feel a sense of well-being, and even suffer injury or death from a car crash. Designing
       communities so that walking and biking are convenient, practical, safe, and enjoyable for
       meeting daily needs can help achieve all of these aims.

Carefully choosing where and how we build can reduce the direct impacts of development on habitat,
ecosystems, and water quality. Land use practices can also reduce indirect impacts on air quality and
global climate by affecting travel choices. As communities nationwide look for ways to reduce the
environmental and human health  impacts of their development decisions, the evidence is clearthat our
nation can continue to grow and can build a strong foundation for lasting prosperity while also
protecting our environment and health.

Works Cited
Adamkiewicz, Gary, et al. "Moving environmental justice indoors: Understanding structural influences on
residential exposure patterns in low-income communities." American Journal of Public Health 101, no. SI (2011):
Aguilar, Ramiro, Mauricio Quesada, Lorena Ashworth, Yvonne Herrerias-Diego, and Jorge Lobo. "Genetic
consequences of habitat fragmentation in plant populations: Susceptible signals in plant traits and methodological
approaches." Molecular Ecology 17, no. 24 (2008): 5177-5188.
Air Force Institute for Environment, Safety, and Occupational Health Risk Analysis. "Fact sheet: Indoor air and risk
assessment." n.d. http://dhl.dhhq.health.mil/Product/RetrieveFile?prodld=32.
Al-Zoughool, Mustafa, and Daniel Krewski. "Health effects of radon: A review of the literature." International
Journal of Radiation Biology 85, no. 1 (2009): 57-69.
Anderson, Brooke G., and Michelle L. Belle. "Weather-related mortality: How heat, cold, and heat waves affect
mortality in the United States." Epidemiology 20 (2009): 205-213.
Arrington, G.B., and Robert Cervero. "Effects of TOD on housing, parking, and travel." Transit Cooperative Research
Program Report 128. Transportation Research Board of the National Academies. 2008.
Bae, Chang-Hee Christine, Gail Sandlin, Alon Bassok, and Sungyop Kim. "The exposure of disadvantaged
populations in freeway air-pollution sheds: A case study of the Seattle and Portland regions." Environment and
Planning B: Planning and Design 34 (2007): 154-170.
Banks, Sam C., Maxine P. Piggott, Adam J. Stow, and Andrea C. Taylor. "Sex and sociality in a disconnected world: A
review of the impacts of habitat fragmentation on animal social interactions." Canadian Journal of Zoology 85, no.
10 (2007): 1065-1079.
Bartholomew, Keith. "Land use-transportation scenario planning: Promise and reality." Transportation 34 (2007):
Bartholomew, Keith, and Reid Ewing. "Land use-transportation scenarios and future vehicle travel and land
consumption: A meta-analysis." Journal of the American Planning Association 75, no. 1 (2008): 13-27.
Basu, Rupa. "High ambient temperature and mortality: A review of epidemiological studies from 2001 to 2008."
Environmental Health 8, no. 40 (2009).
Beal, Cara D., Edoardo Bertone, and Rodney A. Stewart. "Evaluating the energy and carbon reductions resulting
from resource-efficient household stock." Energy and Buildings 55 (2012): 422-432.
Bean, Eban Zachary, William Frederick Hunt, and David Alan Bidelspach. "Evaluation of four permeable pavement
sites in eastern North Carolina for runoff reduction and water quality impacts." Journal of Irrigation and Drainage
Engineering 133, no. 6 (2007): 583-592.
Beaulieu, Karen M., Amanda H. Bell, and James F. Coles. Variability in Stream Chemistry in Relation to Urban
Development and Biological Condition in Seven Metropolitan Areas of the United States, 1999-2004. U.S. Geological
Survey. 2012. http://pubs.usgs.gov/sir/2012/5170/pdf/sir2012-5170_beaulieu_508.pdf.
Bechle, Matthew J., Dylan B. Millet, and Julian D. Marshall. "Effects of income and urban form on urban NO2:
Global evidence from satellites." Environmental Science & Technology 45 (2011): 4914-4919.

                                                                                            Works Cited
Bengston, David N., Jennifer O. Fletcher, and Kristen C. Nelson. "Public policies for managing urban growth and
protecting open space: Policy instruments and lessons learned in the United States." Landscape and Urban
Planning 69, no. 2-3 (2004): 271-286.
Bernstein, Jonathan A., et al. "The health effects of nonindustrial indoor air pollution." Journal of Allergy and
Clinical Immunology 121, no. 3 (2008): 585-591.
Besser, Lilah M., and Andrew L. Dannenberg. "Walking to public transit: Steps to help meet physical activity
recommendations." American Journal of Preventive Medicine 29, no. 4 (2005): 273-280.
Bhat, Chandra R., and Jessica Y. Guo. "A comprehensive analysis of built environment characteristics on household
residential choice and auto ownership levels." Transportation Research Part B: Methodological 41, no. 5 (2007):
Booth, Derek B., and Brian P. Bledsoe. "Streams and urbanization." In The Water Environment of Cities, by L. A.
Baker, 93-123. New York: Springer, 2009.
Brattebo, Benjamin O., and Derek B. Booth. "Long-term stormwater quantity and quality performance of
permeable pavement systems." Water Research 37, no. 18 (2003): 4369-4376.
Bribian,  Ignacio Zabalza, Antonio Valero Capilla, and Alfonso Aranda Uson. "Life cycle assessment of building
materials: Comparative analysis of energy and environmental impacts and evaluation of the eco-efficiency
improvement potential." Building and Environment 46, no. 5 (2011):  1133-1140.
Brown, Barbara B., and Carol M. Werner. "A new rail stop: Tracking moderate physical activity bouts and
ridership." American Journal of Preventive Medicine 33, no. 4 (2007): 306-309.
Brown, Thomas C., and Pamela Froemke. "Nationwide assessment of nonpoint source threats to water quality."
BioScience 62, no. 2 (2012): 136-146.
Buehler, Ralph, and John Pucher. "Cycling to work in 90 large American cities: New evidence on the role of bike
paths and lanes." Transportation 39 (2012): 409-432.
Burghardt, Karin T., Douglas W. Tallamy, and Gregory Shriver. "Impact of native plants on bird and butterfly
biodiversity in suburban landscapes." Conservation Biology 23, no. 1  (2008): 219-224.
Burghardt, Karin T., Douglas W. Tallamy, Christopher Philips,  and Kimberley J. Shropshire. "Non-native plants
reduce abundance, richness, and host specialization in lepidopteran communities." Ecosphere 1, no. 5 (2010): 1-22.
Cao, Xinyu, Patricia L.  Mokhtarian, and Susan L. Handy. "Examining the impacts of residential  self-selection on
travel behavior: A focus on empirical findings." Transport Reviews 29, no. 3 (2009): 359-395.
Carey, Richard O., et al. "Evaluating nutrient impacts in urban watersheds: Challenges and research opportunities."
Environmental Pollution 173 (2013): 138-149.
Carlisle,  Daren M., David M. Wolock, and Michael R. Meador. "Alteration of streamflow magnitudes and potential
ecological consequences: A multiregional assessment." Frontiers in Ecology and the Environment 9, no. 5 (2011):
Centers  for Disease Control and Prevention, National Center for Injury Prevention and Control. WISQARS Fatal
Injury Reports, National and Regional, 1999-2010. http://webappa.cdc.gov/sasweb/ncipc/mortratelO_us.html
(accessed February 11, 2013).
—. WISQARS Nonfatal Injury Reports, http://webappa.cdc.gov/sasweb/ncipc/nfirates2001.html (accessed February
11, 2013).

Works Cited
Cervero, Robert. "Office development, rail transit, and commuting choice." Journal of Public Transportation 9, no. 5
(2006): 41-55.
—. "Road expansion, urban growth, and induced travel: A path analysis." Journal of the American Planning
Association 69, no. 2 (2003): 145-163.
—. "Transit-oriented development's ridership bonus: A product of self-selection and public policies." Environment
and Planning A 39 (2007): 2068-2085.
Cervero, Robert, and Jin Murakami. "Effects of built environments on vehicle miles traveled: Evidence from 370
U.S. urbanized areas." Environment and Planning A 42 (2010): 400-418.
Cervero, Robert, and Michael Duncan. "Which reduces vehicle travel more: Jobs-housing balance or retail-housing
mixing?" Journal of the American Planning Association 72, no. 4 (2006): 475-490.
Chatman, Daniel G. "Residential choice, the built environment, and nonwork travel: Evidence using new data and
methods." Environment and Planning A 41  (2009): 1072-1089.
Chattopadhyay, Sudip, and Emily Taylor. "Do smart growth strategies have a  role in curbing vehicle miles traveled?
A further assessment using household level survey data." The B.E. Journal of Economic Analysis & Policy 12, no. 1
Chen, Li, Cynthia Chen, Reid Ewing, Claire E. McKnight, Raghavan Srinivasan, and Matthew Roe. "Safety
countermeasures and crash reduction in New York City—Experience and lessons learned." Accident Analysis and
Prevention 50 (2013): 312-322.
Chester, Mikhail, Arpad Horvath, and Samer Madanat. "Parking infrastructure: energy, emissions, and automobile
life-cycle environmental accounting." Environmental Research Letters 5 (2010).
Clark, Lara P., Dylan B. Millet, and Julian D.  Marshall. "Air quality and urban form in U.S.  urban areas: Evidence
from regulatory monitors." Environmental Science & Technology 45, no. 16 (2011): 7028-7035.
Cochran, K.M., and T.G. Townsend. "Estimating construction and demolition debris generation using a  materials
flow analysis approach." Waste Management 30, no. 11  (2010): 2247-2254.
Cochran, Kimberly, Timothy Townsend, Debra Reinhart, and Howell Heck. "Estimation of regional building-related
C&D debris generation and composition: Case study for Florida, U.S." Waste Management 27, no. 7 (2007): 921-
Coffin, Alisa W. "From roadkill to road ecology: A review of the ecological effects of roads." Journal of Transport
Geography 15, no. 5 (2007): 396-406.
Colbeck, Ian, and Zaheer Ahmad Nasir. "Indoor air pollution." In Human Exposure to Pollutants via Dermal
Absorption and Inhalation, by Mihalis Lazaridis and Ian Colbeck, 41-72. Springer, 2010.
Coles, James F., Thomas F. Cuffney, Gerard McMahon, and Cornell J. Rosiu. "Judging a brook by its cover: The
relation between ecological condition of a stream and urban land cover in New England." Northeastern Naturalist
17, no. 1 (2010): 29-48.
Costanza, Robert, Octavio Perez-Maqueo, Luisa Martinez, Paul Sutton, Sharolyn J. Anderson, and Kenneth Mulder.
"The value of coastal wetlands for hurricane protection." A Journal of the Human Environment 37, no. 4 (2008):
Grain, Caitlin M., Benjamin S. Halpern, Mike W. Beck, and Carrie V. Kappel. "Understanding and managing human
threats to the coastal marine environment." The Year in Ecology and Conservation  Biology 1162 (2009): 39-62.

                                                                                            Works Cited
Cuffney, Thomas F., Robin A. Brightbill, Jason T. May, and Ian R. Waite. "Responses of benthic macroinvertebrates
to environmental changes associated with urbanization in nine metropolitan areas." Ecological Applications 20, no.
5 (2010): 1384-1401.
Cutts, Bethany B., Kate J. Darby, Christopher G. Boone, and Alexandra Brewis. "City structure, obesity, and
environmental justice: An integrated analysis of physical and social barriers to walkable streets and park access."
Social Science & Medicine 69 (2009): 1314-1322.
Dahl, I.E. Status and Trends of Wetlands in the Conterminous United States 2004 to 2009. U.S. Fish and Wildlife
Service. 2011. http://www.fws.gov/wetlands/Status-And-Trends-2009/index.html.
Dahl, Thomas E. Wetlands Losses in the United States 1780s to 1980s. U.S. Fish and Wildlife Service. 1990.
Davis, Amelie Y.,  Bryan C. Pijanowski, Kimberly Robinson, and Bernard Engel. "The environmental and economic
costs of sprawling parking lots in the United States." Land Use Policy 27 (2010): 255-261.
Davis, Mark A., et al. "Don't judge species on their origins." Nature 474 (2011): 153-154.
Davis, Stacy C., Susan W. Diegel, and Robert G. Boundy. Transportation Energy Data Book: Edition 31. U.S.
Department of Energy. 2012. http://cta.ornl.gov/data/download31.shtml.
de Groot, Rudolfs., Matthew A. Wilson, and Roelof M.J. Boumans. "A typology for the classification, description
and valuation of ecosystem functions, goods and services." Ecological Economics 41 (2002): 393-408.
Defeo, Omar, et al. "Threats to sandy beach ecosystems: A review." Estuarine, Coastal and Shelf Science 81 (2009):
Di Giulio, Manuela, Rolf Hoderegger, and Silvia Tobias. "Effects of habitat and landscape fragmentation on humans
and biodiversity in densely populated landscapes." Journal of Environmental Management 90, no. 10 (2009): 2959-
DiCecio, Riccardo, Kristie M. Engemann, Michael T. Owyang, and Christopher H. Wheeler. "Changing trends in the
labor force: A survey." Federal Reserve Bank of St. Louis Review 90, no. 1 (2008): 47-62.
Dietz, Michael E.  "Low impact development practices: A review of current research and recommendations for
future directions." Water, Air, and Soil Pollution 186, no. 1-4 (2007): 351-363.
Dill, Jennifer. "Transit use at transit-oriented developments in Portland, Oregon, area." Transportation Research
Record 2063 (2008): 159-167.
Dodson, Robin E., et al. "After the PBDE phase-out: A broad suite of flame retardants in repeat house dust samples
from California."  Environmental Science & Technology 46 (2012): 13056-13066.
Dolan, Rebecca W., Marcia E. Moore, and Jessica D. Stephens. "Documenting effects of urbanization on flora using
herbarium records." Journal of Ecology 99, no. 4 (2011): 1055-1062.
Drummond, Mark A., and Thomas R. Loveland. "Land-use pressure and a transition to forest-cover loss in the
Eastern United States." BioScience 60, no. 4 (2010): 286-298.
D'Souza, Jennifer C., Chunrong Jia, Bhrarmar Mukherjee, and Stuart Batterman. "Ethnicity, housing and personal
factors as determinants of VOC exposures." Atmospheric Environment 18, no. 43 (2009): 2884-2892.
Duke, J., M. Huhman, and C. Heitzler. "Physical activity levels among children aged 9-13 years—United States,
2002." Morbidity and Mortality Weekly Report 52, no. 33  (2003): 785-788.

Works Cited
Dulal, Hari Bansha, Gernot Brodnig, and Charity G. Onoriose. "Climate change mitigation in the transport sector
through urban planning: A review." Habitat International 35, no. 3 (2011): 494-500.
Dumbaugh, Eric, and Robert Rae. "Safe urban form: Revisiting the relationship between community design and
traffic safety." Journal of the American Planning Association 75, no. 3 (2009): 309-329.
Dumbaugh, Eric, and Wenhao Li. "Designing for the safety of pedestrians, cyclists, and motorists in urban
environments." Journal of the American Planning Association 77, no. 1 (2010): 69-88.
Duranton, Gilles, and Matthew A. Turner. "The fundamental  law of road congestion: Evidence from U.S. cities."
American Economic Review 101 (2011): 2616-2652.
Durkin, Thomas H. "Boiler system efficiency." ASHRAE Journal 48 (2006): 51-57.
EPA. "1970-2012 average  annual emissions, all criteria pollutants in MS Excel." National Emissions Inventory (NEI)
Air Pollutant Emissions Trends Data. 2012. http://www.epa.gov/ttn/chief/trends/index.html.
—. 2005 National-Scale Air Toxics Assessment, http://www.epa.gov/ttn/atw/nata2005/index.html (accessed
October 31, 2012).
—. About Air Toxics,  http://www.epa.gov/ttn/atw/allabout.html (accessed October 31, 2012).
—. About Energy Star. http://www.energystar.gov/index.cfm?c=about.ab_index (accessed November 8, 2012).
—. Air Emission Sources. 2008. http://www.epa.gov/air/emissions/index.htm (accessed September 24,  2012).
—. "Air toxics pie charts."  2005 Assessment Results. 2011. http://www.epa.gov/ttn/atw/nata2005/tables.html.
—. The Ambient Air Monitoring Program,  http://epa.gov/air/oaqps/qa/monprog.html (accessed April 4, 2013).
—. Cleaning up the Nation's Waste Sites: Markets and Technology Trends.  2004.
—. Design for the Environment, http://www.epa.gov/dfe (accessed February 21, 2013).
—. Distribution System Inventory, Integrity and Water Quality. 2007.
—. Estimating 2003 Building-Related Construction and Demolition Materials Amounts. 2009.
—. FY 2011-2015 EPA Strategic Plan: Achieving Our Vision. 2010.
—. Greenhouse Gas Emissions, http://epa.gov/climatechange/ghgemissions (accessed September 26, 2012).
—. Health Effects of PCBs. http://www.epa.gov/epawaste/hazard/tsd/pcbs/pubs/effects.htm (accessed February
—. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010. 2012.
—. Learn About Asbestos,  http://www2.epa.gov/asbestos/learn-about-asbestos (accessed February 11, 2013).
—. National Ambient Air Quality Standards (NAAQS). http://www.epa.gov/air/criteria.html (accessed September
21, 2012).

                                                                                            Works Cited
—. Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices. 2009.
—. Our Nation's Air: Status and Trends Through 2008.  2010.
—. Our Nation's Air: Status and Trends Through 2010.  2012.
—. Protecting Water Resources with Higher-Density Development. 2006.
—. Residential Construction Trends in America's Metropolitan Regions. 2012.
—. Summary Nonattainment Area Population Exposure Report. 2012.
—. Technical Fact Sheet - Polybrominated Diphenyl Ethers (PBDEs) and Polybrominated Biphenyls (PBBs). 2012.
—. WaterSense. http://www.epa.gov/WaterSense/about_us/index.html (accessed February 26, 2013).
—. WaterSense at Work: Best Management Practices for Commercial and Institutional Facilities. 2012.
http://www.epa. gov/watersense/commercial/docs/watersense_at_work/#/l.
—. Watershed Assessment, Tracking & Environmental  Results.
http://ofmpub.epa.gov/tmdl_waterslO/attains_nation_cy.control (accessed September 10, 2012).
—. What is Green Infrastructure? http://water.epa.gov/infrastructure/greeninfrastructure/gi_what.cfm (accessed
February 13, 2013).
Evans, John E. Traveler Response to Transportation System Changes. Chapter 9—Transit Scheduling and Frequency.
Transportation Research Board of the National Academies. 2004.
Ewing, Reid.  "Highway-induced development: Research results for metropolitan areas." Transportation Research
Record: Journal of the Transportation Research Board  2067 (2008): 101-109.
Ewing, Reid,  and Eric Dumbaugh. "The built environment and traffic safety: A review of empirical evidence."
Journal of Planning Literature 23, no. 4 (2009): 347-367.
Ewing, Reid,  and Robert Cervero. "Travel and the built environment: A meta-analysis." Journal of the American
Planning Association 76, no. 3  (2010): 265-294.
Ewing, Reid,  et al. "Traffic generated by mixed-use developments—Six-region study using consistent built
environment measures." Journal of Urban Planning and Development 137, no. 3 (2011): 248-261.
Ewing, Reid,  Keith Bartholomew, Steve Winkelman, Jerry Walters, and Geoffrey Anderson. "Urban development
and climate change." Journal ofUrbanism 1, no. 3 (2008): 201-216.
Ewing, Reid,  Richard A. Schieber, and Charles V. Zegeer. "Urban sprawl as a risk factor in motor vehicle occupant
and pedestrian fatalities." American Journal of Public Health 93, no. 9 (2003): 1541-1545.
Fan, Yingling, and Asad J. Khattak. "Urban form, individual spatial footprints, and travel: Examination of space-use
behavior." Transportation Research Record 2082 (2008): 98-106.

Works Cited
Farm, Neal, Amy D. Lamson, Susan C. Anenberg, Karen Wesson, David Risley, and Bryan J. Hubbell. "Estimating the
national public health burden associated with exposure to ambient PM2.s and ozone." Risk Analysis 32, no. 1
(2012): 81-95.
Faulkner, Guy E.J., Ron N. Buliung, Parminder K. Flora, and Caroline Fusco. "Active school transport, physical
activity levels and body weight of children and youth: A systematic review." Preventive Medicine 48, no. 1 (2009):
Federal Highway Administration. Data Extraction and Visualization Prototypes, http://nhts.ornl.gov/det (accessed
January 22, 2013).
—. Highway Statistics. 2010. http://www.fhwa.dot.gov/policyinformation/statistics/2010.
—. Historical Monthly VMT Report. March 26, 2012.
—. National Household Travel Survey: Our Nation's Travel, http://nhts.ornl.gov (accessed January 22, 2013).
—. Summary of Travel Trends: 2009 National Household Travel Survey. 2011.
http://nhts.orn I .gov/2009/pu b/stt. pdf.
—. Wildlife-Vehicle Collision Reduction Study: Report To Congress. 2008.
Federal Interagency Stream Restoration Working Group. Stream Corridor Restoration: Principles, Processes, and
Practices. 1998.
Feng, Jing, Thomas A. Glass, Frank C. Curriero, Walter F. Steward, and Brian A. Schwartz. "The built environment
and obesity: A systematic review of the epidemiologic evidence." Health & Place 16 (2010): 175-190.
Ferdinand, Alva O., Bisakha Sen, Saurabh Rahurkar, Sally Engler, and Nir Menachemi. "The relationship between
built environments and physical activity: A systematic review." American Journal of Public Health 102, no. 10
Fischer, Joern, and David B. Lindenmayer. "Landscape modification and habitat fragmentation: A synthesis." Global
Ecology and Biogeography 16, no. 3 (2007): 265-280.
Fitzpatrick, Faith A., and Marie C.  Peppier. Relation of Urbanization to Stream Habitat and Geomorphic
Characteristics in Nine Metropolitan Areas of the United States. U.S. Geological Survey. 2010.
Flegal, Katherine M., Margaret D. Carroll, Cynthia L. Ogden, and Lester R.  Curtin. "Prevalence and trends in obesity
among U.S. adults, 1999-2008." The Journal of the American Medical Association 303, no. 3 (2010): 235-241.
Forman, Richard T.T. "Estimate of the area affected ecologically by the road system in the United States."
Conservation  Biology 14, no. 1 (2000): 31-35.
Forman, Richard T.T., and Robert D. Deblinger. "The ecological road-effect zone of a Massachusetts (U.S.A.)
suburban highway." Conservation Biology 14, no. 1 (2000): 36-46.
Forman, Richard T.T., et al. Road Ecology: Science and Solutions. Washington: Island Press, 2003.
Frank, Lawrence D., and Peter Engelke. "Multiple impacts of the built environment on public health: Walkable
places and the exposure to air pollution." International Regional Science Review 28, no. 2 (2005): 193-216.

                                                                                             Works Cited
Frank, Lawrence D., James F. Sallis, Terry L. Conway, James E. Chapman, and Brian E. Saelens. "Many pathways
from land use to health: Associations between neighborhood walkability and active transportation, body mass
index, and air quality." Journal of the American Planning Association 72, no. 1 (2006): 75-87.
Frazer, Lance. "Paving paradise: The peril of impervious surfaces." Environmental Health Perspectives 113, no. 7
Frumkin, Howard. "Cities, suburbs, and urban sprawl: Their impact on health." In Cities and the Health of the
Public, by Nicholas Freudenberg and Sandro Galea, 143-175. Vanderbilt University Press, 2006.
Frumkin, Howard. "Urban sprawl and public health." Public Health Reports 117 (2002): 201-217.
Fuentes-Leonarte, Virginia, Jose M. Tenias, and Ferran Ballester. "Levels of pollutants in indoor air and respiratory
health in preschool children: A systematic review." Pediatric Pulmonology 44 (2009): 231-243.
Gebel, Klaus, Adrian E. Bauman, and Mark Petticrew. "The physical environment and physical activity: A critical
appraisal of review articles." American Journal of Preventive Medicine 32, no. 5 (2007): 361-369.
Giles, Luisa V., et al. "From good intentions to proven interventions: Effectiveness of actions to reduce the health
impacts of air pollution." Environmental Health Perspectives 199, no. 1 (2011): 29-36.
Gilliom, Robert J., et al. Pesticides in the Nation's Streams and Ground Water 1992-2001. U.S. Geological Survey.
2006. http://pubs.usgs.gov/circ/2005/1291/pdf/circl291.pdf.
Gim, Tae-Hyoung Tommy. "A meta-analysis of the relationship between density and travel behavior."
Transportation 39 (2012): 491-519.
Gordon-Larson, Penny,  Melissa C. Nelson, Phil Page, and  Barry M. Popkin. "Inequality in the built environment
underlies key health disparities in physical activity and obesity." Pediatrics 117, no. 2 (2006): 417-424.
Gregory, Justin H., Michael D. Dukes, Pierce H. Jones, and Grady L. Miller. "Effect of urban soil compaction on
infiltration rate." Journal of Soil and Water Conservation 61,  no. 3 (2006): 117-124.
Haley, Melissa B., Michael D. Dukes, and Grady L. Miller. "Residential irrigation water use in central Florida."
Journal of Irrigation and Drainage Engineering 133, no. 5 (2007): 427-434.
Handy, Susan. "Smart growth and the transportation-land use connection: What does the research tell us?"
International Regional Science Review 28, no. 2 (2005): 146-167.
Harvey, L.D. Danny. "Reducing energy use in the buildings sector: Measures, costs, and examples." Energy
Efficiency 2 (2009): 139-163.
Hassan, Rashid, Robert  Scholes, and Neville Ash. Ecosystems and Human Well-being: Current State and Trends,
Volume 1. Island Press.  2005. http://www.unep.org/maweb/en/Condition.aspx.
Hatt, Belinda E., Tim D.  Fletcher, Christopher J. Walsh,  and Sally I. Taylor. "The influence of urban density and
drainage infrastructure on the concentrations and loads of pollutants in small streams." Environmental
Management 34, no. 1  (2004): 112-124.
Heath, Gregory W., Ross C. Brownson, Judy Kruger, Rebecca Miles, Kenneth E. Powell, and Leigh T. Ramsey. "The
effectiveness of urban design and land use and transport policies and practices to increase physical activity: A
systematic review." Journal of Physical Activity and Health 3, no. Suppl 1 (2006): S55-S76.
Hickman, Jonathan E., Shiliang Wu, Loretta J. Mickley, and Manuel T. Lerdau. "Kudzu (Pueraria montana) invasion
doubles emissions of nitric oxide and increases ozone pollution." Proceedings of the National Academy of Sciences
107, no. 22 (2010): 10115-10119.

Works Cited
Horvath, Arpad. "Construction materials and the environment." Annual Review of Environment and Resources 29
(2004): 181-204.
Hostetler, Mark E., and Martin B. Main. "Native landscaping vs. exotic landscaping: What should we recommend?"
Journal of Extension 45, no. 5 (2010).
Hun, Diana E., Jeffrey A. Siegel, Maria T. Morandi, Thomas H. Stock, and Richard L. Corsi. "Cancer risk disparities
between Hispanic and non-Hispanic white populations: The role of exposure to indoor air pollution."
Environmental Health Perspectives 117, no. 12 (2009): 1925-1931.
Hurd, Brian H. "Water conservation and residential landscapes: Household preferences, household choices."
Journal of Agricultural and Resource Economics 31, no. 2 (2006): 173-192.
Intergovernmental Panel on Climate Change. Climate Change 2007: Synthesis Report. 2007.
Jackson, Laura E. "The relationship of urban design to human health and condition." Landscape and Urban
Planning 64 (2003): 191-200.
Jacob, John S., and Ricardo Lopez. "Is denser greener? An evaluation of higher density development as an urban
stormwater-quality best management practice." Journal of the American Water Resources Association 45, no. 3
(2009): 687-701.
Jacobson, Carol R. "Identification and quantification of the hydrological impacts of imperviousness in urban
catchments: A review." Journal of Environmental Management 92, no. 6 (2011): 1438-1448.
James, J.P., and X. Yang. "Emissions of volatile organic compounds from several green and non-green building
materials: A comparison." Indoor and Built Environment 14, no. 1 (2004): 69-74.
Johnson, Paula I., Heather M. Stapleton, Andreas Sjodin, and John D. Meeker. "Relationships between
polybrominated diphenyl ether and concentrations in house dust and serum." Environmental Science & Technology
44, no. 14 (2010): 5627-5632.
Jun, Myung-Jin. "Are Portland's smart growth policies related to reduced automobile dependence?" Journal of
Planning Education and Research 28 (2008): 100-107.
Kahyaoglu-Koracin, Julide, Scott D. Bassett, David A. Mouat, and Alan W. Gertler. "Application of a scenario-based
modeling system to evaluate the air quality impacts of future growth." Atmospheric Environment 43, no. 5 (2009):
Keddy, Paul A. Wetland Ecology: Principles and Conservation. 2nd. Cambridge, UK: Cambridge University Press,
Kenny, Joan F., Nancy L. Barber, Susan S. Hutson, Kristin S. Linsey, John K. Lovelace, and Molly A. Maupin.
Estimated Use of Water in the United States in 2005. U.S. Geological Survey. 2009. http://pubs.usgs.gov/circ/1344.
King, Ryan S.,  Matthew E. Baker, Paul F. Kazyak, and Donald E. Weller. "How novel is too novel? Stream community
thresholds at exceptionally low levels of catchment urbanization." Ecological Applications 21, no. 5 (2011): 1659-
Kockelman, Kara, Matthew Bomberg, Melissa Thompson, and Charlotte Whitehead. GHG emissions control
options: Opportunities for conservation. Commissioned for Driving and the Built Environment:  The Effects of
Compact Development on Motorized Travel, Energy Use, and CO2 Emissions—Special Report 298. National
Academy of Sciences. 2009. http://onlinepubs.trb.org/Onlinepubs/sr/sr298kockelman.pdf.

                                                                                            Works Cited
Krizek, Kevin J. "Residential relocation and changes in urban travel: Does neighborhood-scale urban form matter?"
Journal of the American Planning Association 69, no. 3 (2003): 265-281.
Kuzmyak, J. Richard, Richard H. Pratt, G. Bruce Douglas, and Frank Spielberg. Traveler Response to Transportation
System Changes: Chapter 15—Land Use and Site Design. Transportation Research Board. 2003.
Landis, John D., Heather Hood, Guangyu Li, Thomas Rogers, and Charles Warren. "The future of infill housing in
California: Opportunities, potential, and feasibility." Housing Policy Debate 17, no. 4 (2006): 681-726.
Lavoie, Emma T., et al. "Chemical alternatives assessment: Enabling substitution to safer chemicals."
Environmental Science & Technology 44, no. 24 (2010): 9244-9249.
Lee, Mengshan, and Berrin Tansel. "Life cycle based analysis of demands and emissions for residential water-using
appliances." Journal of Environmental Management 101 (2012): 75-81.
Lee, Sangyun, and Paul Mohai. "Racial and socioeconomic assessments of neighborhoods adjacent to small-scale
brownfield sites in the Detroit region." Environmental Practice 13 (2011): 340-353.
Leigh, Nancey Green, and Sarah L. Coffin.  "Modeling the relationship among brownfields, property values, and
community revitalization." Housing Policy Debate 16, no. 2 (2005): 257-280.
Lerman, Susannah B., and Paige S. Warren. "The conservation value of residential yards: Linking birds and people."
Ecological Applications 21, no. 4 (2011): 1327-1339.
Levine, Jonathan, and Lawrence D. Frank.  "Transportation and land-use preferences and residents' neighborhood
choices: The sufficiency of compact development in the Atlanta region."  Transportation 34 (2007): 255-274.
Levine, Jonathan, Aseem Inam, and Gwo-Wei Torng. "A choice-based rationale for land  use and transportation
alternatives: Evidence from Boston and Atlanta." Journal of Planning Education and Research 24 (2005): 317-330.
Lewis, Paul, William  Rasdorf, H. Christopher Frey, Shih-Hao  Pang, and Kangwook Kim. "Requirements and
incentives for reducing construction vehicle emissions and comparison of nonroad diesel engine emissions data
sources." Journal of Construction Engineering and Management 135, no. 5 (2009): 341-351.
Li, Fuzhong, et al. "Built environment,  adiposity, and physical activity in adults aged 50-75." American Journal of
Preventive Medicine 35, no. 1 (2008): 38-46.
Line, D.E., and  N.M. White. "Effects of development on runoff and pollutant export." Water Environment Research
79, no. 2 (2007): 185-190.
LoGiudice, Kathleen, Richard S. Ostfeld, Kenneth A. Schmidt, and Felicia Keesing. "The ecology of infectious
disease: Effects of host diversity and community composition on Lyme disease risk." Proceedings of the National
Academy of Sciences 100, no. 2 (2003): 567-571.
Lubans, David R., Colin A. Boreham, Paul Kelly, and Charlie E. Foster. "The relationship between active travel to
school and health-related fitness in children and adolescents: A systematic review." International Journal of
Behavioral Nutrition and Physical Activity  8, no. 5 (2011): 1-12.
Lubeck, Aaron, and Francis Conlin. "Efficiency and comfort through deep energy retrofits: Balancing energy and
moisture management." Journal of Green Building 3, no. 5 (2010).
MacDonald, John M., Robert J. Stokes, Deborah A. Cohen, Aaron Kofner,  and Gred K. Ridgeway. "The effect of light
rail transit on body mass index and physical activity." American Journal of Preventive Medicine 39, no.  2  (2010):

Works Cited
Mahmoud, Mohammed, et al. "A formal framework for scenario development in support of environmental
decision-making." Environmental Modelling & Software 24, no. 7 (2009): 798-808.
Manville, Michael, and Donald Shoup. "Parking, people, and cities." Journal of American Planning and Development
131, no. 4 (2005): 233-245.
Marshall, Julian D. "Energy-efficient urban form: Reducing urban sprawl could play an important role in addressing
climate change." Environmental Science & Technology 42, no. 9 (2008): 3133-3137.
Marshall, Julian D., Michael Brauer, and Lawrence D. Frank. "Healthy neighborhoods: Walkability and air
pollution." Environmental Health Perspectives 117, no. 11 (2009): 1752-1759.
Marshall, Julian D., Thomas E. McKone, Elizabeth Deakin, and William W. Nazaroff. "Inhalation of motor vehicle
emissions: Effects of urban population and land area." Atmospheric Environment 39, no.  2 (2005): 283-295.
Massada, Avi Bar, Volker C. Radeloff, Susan I. Stewart, and Todd J. Hawbaker. "Wildfire risk in the wildland-urban
interface:  A simulation study in northwestern Wisconsin." Forest Ecology and Management 258, no. 9 (2009):
McCarthy, Linda. "Efficiency in targeting the most marketable sites rather than equity in  public assistance for
brownfield redevelopment." Economic Development Quarterly 23, no. 3 (2009): 211-228.
McConville, Megan E., Daniel A. Rodriguez, Kelly Clifton, Gihyoug Cho, and Sheila Fleischhacker. "Disaggregate land
uses and walking." American Journal of Preventive Medicine 40, no. 1 (2011): 25-32.
McDonald, Noreen C., Austin L. Brown, Lauren M. Marchetti, and Margo S. Pedroso. "U.S. school travel, 2009: An
assessment of trends." American Journal of Preventive Medicine, 2011: 146-151.
McKinney, Michael L. "Urbanization as a major cause of biotic homogenization." Biological Conservation 127
(2006): 247-260.
Memmott, Jeffery.  Trends in Personal Income and Passenger Vehicle Miles.  Bureau of Transportation Statistics.
Mendell, M.J. "Indoor residential chemical emissions as risk factors for respiratory and allergic effects in children: A
review." Indoor Air 17, no. 4 (2007): 259-277.
Mendell, Mark J., Anna G. Mirer, Kerry Cheung, My Tong, and Jeroen Douwes. "Respiratory and allergic health
effects of dampness, mold, and dampness-related agents: A review of the epidemiologic evidence." Environmental
Health Perspectives 119, no. 6 (2011): 748-756.
Metz, David. "The myth of travel time saving." Transport Reviews 28, no. 3 (2008): 321-336.
Millard-Ball, Adam, and Lee Schipper. "Are we reaching peak travel? Trends in passenger transport in eight
industrialized countries." Transport Reviews 31, no. 3 (2011): 357-378.
Miranda, Marie Lynn, Sharon E. Edwards, Martha H. Keating, and Christopher J. Paul. "Making the environmental
justice grade: The relative burden of air pollution exposure in the United States." International Journal of
Environmental Research and Public Health 8 (2011): 1755-1771.
Mokhtarian, Patricia L.,  Franciso  J. Samaniego, Robert H. Shumway, and Neil H. Willits. "Revisiting the notion of
induced traffic through a matched-pairs study." Transportation 29 (2002): 193-220.
Moore, Latetia V., Ana V. Diez Roux, Kelly R. Evenson, Aileen P. McGinn, and Shannon J. Brines. "Availability of
recreational resources in minority and low socioeconomic status areas." American Journal of Preventive Medicine
34, no. 1 (2008): 16-22.

                                                                                            Works Cited
Moran, Patrick W., et al. Contaminants in Stream Sediments from Seven U.S. Metropolitan Areas: Data Summary of
a National Pilot Study. U.S. Geological Survey. 2012. http://pubs.usgs.gov/sir/2011/5092.
Muench, Stephen T. "Roadway construction sustainability impacts: Review of life-cycle assessments."
Transportation Research Record 2151 (2010): 36-45.
Mukhija, Vinit, and Donald Shoup. "Quantity versus quality in off-street parking requirements." Journal of the
American Planning Association 72, no. 3  (2006): 296-308.
Myers, Dowell, and John Pitkin. "Demographic forces and turning points in the American city, 1950-2040." The
Annals of the American Academy of Political and Social Science 626, no. 1 (2009): 91-111.
National  Highway Traffic Safety Administration. CAFE- Fuel Economy, http://www.nhtsa.gov/fuel-economy
(accessed February 26, 2013).
—. FARS  Data Tables: Summary. http://www-fars.nhtsa.dot.gov/Main/index.aspx (accessed October 4, 2012).
—. Traffic Safety Facts 2000. 2001. http://www-nrd.nhtsa.dot.gov/Pubs/TSF2000.pdf.
—. Traffic Safety Facts 2010. 2012. http://www-nrd.nhtsa.dot.gov/Pubs/811659.pdf.
National  Invasive Species Council. Welcome to lnvasiveSpecies.gov. http://invasivespecies.gov (accessed March 25,
National  Oceanic and Atmospheric Administration. Climate: U.S. Population in the Coastal Floodplain.
http://stateofthecoast.noaa.gov/poplOOyr/welcome.html (accessed February 14, 2013).
—. Climate: Vulnerability of our Nation's Coasts to Sea Level Rise.
http://stateofthecoast.noaa.gov/vulnerability/welcome.html (accessed February 14, 2013).
—. National Coastal Population Report: Population Trends from 1970 to 2020. 2013.
National  Research Council of the National Academies. America's Climate Choices. The National Academies Press.
2011. http://nas-sites.org/americasclimatechoices/sample-page/panel-reports/americas-climate-choices-final-
—. Driving and the Built Environment: The Effects of Compact Development on Motorized Travel, Energy Use, and
CO2 Emissions—Special Report 298. Transportation Research Board. 2009.
—. Urban Stormwater Management in the United States. The National Academies Press. 2009.
Nawaz, Muhammad Farrakh, Guilhem Bourrie, and Fabienne Trolard. "Soil compaction impact and modelling. A
review." Agronomy for Sustainable Development 33, no. 2 (2013): 291-309.
Nelson, Arthur C. "The new urbanity: The rise of a new America." The Annals of the American Academy of Political
and Social Science 626 (2009): 192-208.
Niemeier, Deb, Song Bai, and Susan Handy. "The impact of residential growth patterns on vehicle travel and
pollutant emissions." The Journal of Transport and Land Use 4,  no. 3  (2011): 65-80.
Noland, Robert B., and Lewison L. Lem. "A review of the evidence for induced travel and changes in transportation
and environmental policy in the U.S. and the U.K." Transportation Research Part D:  Transport and Environment 7,
no. 1 (2002): 1-26.

Works Cited
Norman, Jonathan, Heather L. Maclean, and Christopher A. Kennedy. "Comparing high and low residential density:
Life-cycle analysis of energy use and greenhouse gas emissions." Journal of Urban Planning and Development 132,
no. 1 (2006): 10-21.
Nowak, David J., and Eric J. Greenfield. "Tree and impervious cover change in U.S. cities." Urban Forestry & Urban
Greening 11 (2012): 21-30.
Nowak, David J., and Jeffrey T. Walton. "Projected urban growth (2000-2050) and its estimated impact on the U.S.
forest resource." Journal of Forestry 103, no. 8 (2005): 383-389.
Ochoa, Luis, Chris Hendrickson, and Scott Matthews. "Economic input-output life-cycle assessment of U.S.
residential buildings." Journal of Infrastructure Systems 8, no. 4 (2002): 132-138.
Ogden, Cynthia L., and Margaret D. Carroll. Prevalence of Overweight, Obesity, and Extreme Obesity Among Adults:
United States, Trends 1960-1962 Through 2007-2008. National Center for Health  Statistics. 2010.
Ory, David T., Patricia L. Mokhtarian, Lothlorien S. Redmond, Man Salomon, Gustavo O. Collantes, and Sangho
Choo. "When is commuting desirable to the individual?" Growth and Change 35,  no. 3 (2004): 334-359.
Page, G.W., and R.S. Berger. "Characteristics and land use of contaminated brownfield properties in voluntary
cleanup agreement programs." Land Use Policy 23, no. 4 (2006): 551-559.
Perez-Padilla, R., A. Schilmann, and H. Riojas-Rodriguez. "Respiratory health effects of indoor air pollution." The
International Journal of Tuberculosis and Lung Disease 14, no. 9 (2010): 1079-1086.
Pickett, S.T.A., et al. "Urban ecological systems: Scientific foundations and a decade of progress." Journal of
Environmental Management 92, no. 3 (2011): 331-362.
Pimentel, David, Rodolfo Zuniga, and Doug Morrison. "Update on the environmental and economic costs
associated with alien-invasive species in the United States." Ecological Economics 52, no. 3 (2005): 273-288.
Poff, N.  LeRoy, Brian P. Bledsoe, and Christopher O.  Cuhaciyan. "Hydrologic variation with land use across the
contiguous United States: Geomorphic and ecological consequences for stream ecosystems." Geomorphology 79
(2006): 264-285.
Powell, Scott L., Warren B. Cohen, Zhiqiang Yang, John D. Pierce, and Marina Alberti. "Quantification of impervious
surface in the Snohomish Water Resources Inventory Area of western Washington from 1972-2006." Remote
Sensing of Environment 112, no. 4 (2008): 1895-1908.
Pratt, Richard H., and John E. Evans. Traveler Response to Transportation System  Changes. Chapter 10—Bus
Routing and Coverage. Transportation Research Board of the National Academies. 2004.
Price, Katie. "Effects of watershed topography, soils, land use, and climate on baseflow hydrology in humid
regions: A review." Progress in Physical Geography 35, no. 4 (2011): 465-492.
Pucher, John, Jennifer Dill, and Susan Handy. "Infrastructure, programs, and policies to increase bicycling: An
international review." Preventive Medicine 50 (2010): S106-S125.
Pysek, Petr, and David M. Richardson. "Invasive species, environmental change and management, and  health."
Annual Review of Environment and Resources 35 (2010): 25-55.
Pysek, Petr, et al. "A global assessment of invasive plant impacts on resident species, communities and
ecosystems: The  interaction of impact measures, invading species' traits and environment." Global Change Biology
18 (2012): 1725-1737.

                                                                                             Works Cited
Radeloff, Volker C., et al. "Housing growth in and near United States protected areas limits their conservation
value." Proceedings of the National Academy of Sciences 107, no. 2 (2010): 940-945.
Rahman, Maureen Mahbub, and Bliss L. Tracy. "Radon control systems in existing and new construction: A review."
Radiation Protection Dosimetry 135, no. 4 (2009): 243-255.
Ramankutty, Navin, Elizabeth Heller, and Jeanine Rhemtulla. "Prevailing myths about agricultural abandonment
and forest regrowth in the United States." Annals of the Association of American Geographers 100, no. 3 (2010):
Redmond, Lothlorien S., and Patricia L. Mokhtarian. "The positive utility of the commute: Modeling ideal commute
time and relative desired commute amount." Transportation 28, no. 2 (2001): 179-205.
Reynolds, Conor C.O., M. Anne Harris, Kay Teschke, Peter A. Cripton, and Meghan Winters. "The impact of
transportation infrastructure on bicycling injuries and crashes: A review of the literature." Environmental Health 8
(2009): 1-19.
Riitters, Kurt H., and James D. Wickham. "How far to the nearest road?" Frontiers in Ecology and the Environment
1, no. 3 (2003): 125-129.
Rodier, Caroline. "Transit, land use, and auto pricing strategies to reduce vehicle miles traveled and greenhouse
gas emissions." Transportation Research Record: Journal of the Transportation Research Board 2132 (2009): 1-12.
Rodriguez, Daniel A., Kelly R. Evenson, Ana V. Roux, and Shannon J. Brines. "Land use, residential density, and
walking: The multi-ethnic study of atherosclerosis." American Journal of Preventive Medicine 37, no. 5 (2009): 397-
Rogers, Shannon H., John M. Halstead, Kevin H. Gardner, and Cynthia H. Carlson. "Examining walkability and social
capital as indicators of quality of life at the municipal and neighborhood scales." Applied Research in Quality of Life
6 (2011): 201-213.
Rosen, Erik, Helena Stigson, and Ulrich Sander. "Literature review of pedestrian fatality risk as a function of car
impact speed." Accident Analysis and Prevention 43 (2011): 25-33.
Rowe, D. Bradley. "Green roofs as a means of pollution abatement." Environmental Pollution 159, no. 8-9 (2011):
Rudel, Ruthann A.,  and Laura J. Perovich.  "Endocrine disrupting  chemicals in indoor and outdoor air." Atmospheric
Environment 43, no. 1 (2009): 170-181.
Saelens, Brian  E., and Susan L.  Handy. "Built environment correlates of walking: A  review." Medicine and Science in
Sports and Exercise 40, no.  7 (2008): S550-S566.
Sailor, David J., Timothy B. Elley, and Max Gibson. "Exploring the building energy impacts of green roof design
decisions—A modeling study of buildings  in four distinct climates." Journal of Building Physics 35, no. 4 (2012):
Salon, Deborah, Marlon G.  Boarnet, Susan Handy, Steven Spears, and Gil Tal. "How do local actions affect VMT? A
critical review  of the empirical evidence." Transportation Research Part D 17 (2012): 495-508.
Sanchez, Maria C., Richard E. Brown, Carrie Webber, and Gregory K. Homan. "Savings estimates for the United
States Environmental Protection Agency's ENERGY STAR voluntary product labeling program." Energy Policy 36, no.
6 (2008): 2098-2108.

Works Cited
Sandel, Megan, et al. "Housing interventions and control of health-related chemical agents: A review of the
evidence." Journal of Public Health Management & Practice 16, no. 5 (2010): S24-S33.
Sanders, Kelly T., and Michael E. Webber. "Evaluating the energy consumed for water use in the United States."
Environmental Research Letters 7 (2012).
Sawyer, Robert F. "Vehicle emissions: Progress and challenges." Journal of Exposure and Environmental
Epidemiology 20 (2010): 487-488.
Schueler, Thomas R. "The importance of imperviousness." Watershed Protection Techniques 1, no. 3 (1994): 100-
Schueler, Thomas R., Lisa Fraley-McNeal, and Karen Cappiella. "Is impervious cover still important? Review of
recent research." Journal of Hydrologic Engineering 14, no. 4 (2009): 309-315.
Schweitzer, Lisa,  and Jiangping Zhou. "Neighborhood air quality, respiratory health, and vulnerable populations in
compact and sprawled regions." Journal of the American Planning Association 76, no. 3 (2010): 363-371.
Sciera, Katherine L., et al. "Impact of land disturbance on aquatic ecosystem health: Quantifying the cascade of
events." Integrated Environmental Assessment and Management 4, no. 4 (2008): 431-442.
Shen, Li-Yin, Jian Li Hao, Vivian Wing-Van Tarn, and Hong Yao. "A checklist of assessing sustainability performance
of construction projects." Journal of Civil Engineering and Management 13, no. 4 (2007): 273-281.
Short, John Rennie. "Metropolitan USA: Evidence from the 2010 Census." International Journal of Population
Research 2012, (2012).
Simberloff, Daniel. "Non-natives: 141 scientists object." Nature 475 (2011): 36.
Sister, Chona, Jennifer Wolch, and John Wilson. "Got green? Addressing environmental justice in park provision."
Geojournal 75, no. 3 (2010): 229-248.
Smith, W. Brad, and David Darr. U.S. Forest Resource Facts and Historical Trends. U.S. Forest Service. 2004.
http://www.fia.fs.fed.us/libra ry/briefings-summaries-overviews/docs/2002_ForestStats_%20FS801.pdf.
Smith, W. Brad, Patrick D. Miles, Charles H. Perry, and Scott A. Pugh. Forest Resources of the United States, 2007.
U.S. Forest Service. 2009. http://www.nrs.fs.fed.us/pubs/7334.
Southworth, Frank, and Anthon Sonnenberg. "Set of comparable carbon footprints for highway travel in
metropolitan America." Journal of Transportation Engineering 137, no. 6 (2011): 426-435.
Sperry, Benjamin R., Mark W. Burris, and Eric Dumbaugh. "A case study of induced trips at mixed-use
developments." Environment and Planning B: Planning and Design 39, no.  4 (2012): 698-712.
Spielman, Derek, Barry W. Brook,  and Richard  Frankham.  "Most  species are not driven to extinction before genetic
factors impact them." Proceedings of the National Academies of Science 101, no. 42 (2004): 15261-15264.
Sprague,  Lori A., Douglas A. Harned, David W.  Hall, Lisa H. Nowell, Nancy J. Bauch, and Kevin D. Richards. Response
of Stream Chemistry During Base Flow to Gradients of Urbanization in Selected Locations Across the Conterminous
United States, 2002-04. U.S. Geological Survey. 2007. http://pubs.usgs.gov/sir/2007/5083.
Stedman, Susan-Marie, and Thomas E. Dahl. Status and Trends of Wetlands in the Coastal Watersheds of the
Eastern United States 1998 to 2004. National Oceanic and Atmospheric Administration;  National Marine Fisheries
Service; and U.S. Department of the Interior, Fish and Wildlife Service. 2008.

                                                                                            Works Cited
Stone, Brian. "Urban sprawl and air quality in large U.S. cities." Journal of Environmental Management 86, no. 4
(2008): 688-698.
Stone, Brian, Adam C. Mednick, Tracey Holloway, and Scott N. Spak. "Is compact growth good for air quality?"
Journal of the American Planning Association 73, no. 4 (2007): 404-418.
Stone, Brian, Adam C. Mednick, Tracey Holloway, and Scott N. Spak. "Mobile source CO2 mitigation through smart
growth development and vehicle fleet hybridization." Environmental Science & Technology 43, no. 6 (2009): 1704-
Stone, Brian, and John M. Norman. "Land use planning and surface heat island formation: A parcel-based radiation
flux approach." Atmospheric Environment 40 (2006): 3561-3573.
Stone, Brian, Jeremy J. Hess, and Howard Frumkin. "Urban form and extreme heat events: Are sprawling cities
more vulnerable to climate change than  compact cities?" Environmental Health Perspectives 118, no. 10 (2010):
Subramanian, Rajesh. "Motor vehicle traffic crashes as a leading cause of death  in the United States, 2007." Traffic
Safety Facts. National Highway Traffic Safety Administration. 2011. http://www-
Suding, Katharine N. "Toward an era of restoration in ecology: Successes, failures, and opportunities ahead."
Annual Review of Ecology, Evolution, and Systematics 42 (2011): 465-487.
Sutton, Paul C., Sharolyn J. Anderson, Christopher D. Elvidge, Benjamin T. Tuttle, and Tilottama Ghosh. "Paving the
planet: Impervious surface as proxy  measure of the human ecological footprint." Progress in Physical Geography
33, no. 4 (2009): 510-527.
Tallamy, Douglas W., and Kimberley J. Shropshire. "Ranking lepidopteran use of native versus introduced plants."
Conservation Biology 23, no. 4 (2009): 941-947.
Taylor, Brian D., Douglas Miller, Hiroyuki Iseki, and Camille Fink. "Nature and/or nurture? Analyzing the
determinants of transit ridership." Transportation Research Part A: Policy and Practice 43, no. 1 (2009): 60-77.
Theobald, David M., and William H. Romme. "Expansion of the U.S. wildland-urban  interface."  Landscape and
Urban Planning 83, no. 4 (2007): 340-354.
Theobald, David M., Scott J. Goetz, John  B. Norman, and Patrick Jantz. "Watersheds at risk to increased impervious
surface cover in the conterminous United States." Journal of Hydrologic Engineering 14, no. 4 (2009): 362-368.
Tiefenthaler, Liesl L, Eric D. Stein, and Kenneth C. Schiff. "Watershed and land use-based sources of trace metals in
urban storm water." Environmental Toxicology and Chemistry 27, no. 2 (2008): 277-287.
Transportation Research Board of the National Academies. Climate Change and Transportation: Summary of Key
Information. 2012. http://onlinepubs.trb.org/onlinepubs/circulars/ecl64.pdf.
—. Land Use and Site Design: Traveler Response to Transportation System Changes. 2003.
Trojan, Michael D. "Land use impacts on  groundwater quality." Water Encyclopedia 5 (2005): 250-253.
Trojan, Michael D., Jennifer S. Maloney, James M. Stockinger, Erin P.  Eid, and Mark J. Lahtinen. "Effects of land use
on ground water quality in the Anoka Sand Plain Aquifer of Minnesota." Ground Water 41, no. 4 (2003): 482-492.
Tzoulas, Konstantinos, et al. "Promoting  ecosystem and human health in urban areas using green infrastructure: A
literature review." Landscape and Urban Planning 81, no. 3 (2007): 167-178.

Works Cited
United States Conference of Mayors. Recycling America's Land: A National Report On Brownfields Redevelopment,
Volume VII. 2008. http://www.usmayors.org/brownfields/brownfields_bp08.pdf.
—. Vacant and Abandoned Properties: Survey and Best Practices. 2009.
U.S. Census Bureau. 1940 Census of Population and Housing—Families. 1943.
—. 1980 Census of Population: United States Summary. 1983.
http://www2.census.gov/prod2/decennial/documents/1980/1980censusof popu8011uns_bw.pdf.
—. 1990 Census of Population and Housing: Population and Housing Unit Counts United States. 1993.
—. 2010 Census Urban and Rural Classification and Urban Area Criteria.
http://www.census.gov/geo/reference/ua/urban-rural-2010.html (accessed Augusts, 2012).
— .American FactFinder. http://factfinder2.census.gov/faces/nav/jsf/pages/index.xhtml (accessed February 4,
—. "American housing survey for the United States: 2009." Current Housing Reports, Series H150/09. 2010.
—. Annual Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1,
2000 to July 1, 2009. 2009.  http://www.census.gov/popest/data/historical/2000s/vintage_2009/index.html.
—. Changes in Urbanized Areas from 2000 to 2010. 2010. http://www2.census.gov/geo/ua/PopAreaChngeUA.xls.
—. Commuting in the United States: 2009. 2011. http://www.census.gov/prod/2011pubs/acs-15.pdf.
—. Current Population Survey. 2011. http://www.census.gov/population/socdemo/hh-fam/hh6.xls.
—. Historical Census of Housing Tables: Living Alone.
http://www.census.gov/hhes/www/housing/census/historic/livalone.html (accessed February 4, 2013).
—. Historical Census of Housing Tables: Units in Structure.
http://www.census.gov/hhes/www/housing/census/historic/units.html (accessed January 2, 2013).
—. Historical National Population  Estimates: July 1, 1990 to July 1, 1999. 2000.
—. Housing Characteristics: 2010.  2011. http://www.census.gov/prod/cen2010/briefs/c2010br-07.pdf.
—. Means of Transportation to Work for the U.S.
http://www.census.gov/hhes/commuting/files/1990/mode6790.txt (accessed February 28, 2013).
—. Median and Average Square Feet of Floor Area in New Single-Family Houses Completed by Location, n.d.
—. "Notice of final program criteria." Federal Register, August 24, 2011: 53029-53043.
—. Percent Urban and Rural in 2010 by State. 2010. http://www2.census.gov/geo/ua/PctUrbanRural_State.xls.
—. POP Culture: 1900. n.d.  http://www.census.gov/history/pdf/History_1900.pdf.
—. Population and Housing Unit Estimates, http://www.census.gov/popest (accessed August 13, 2012).

                                                                                            Works Cited
—. Population and Land Area of Urbanized Areas, for the United States: 1970 and 1960. 1979.
—. "Population of urbanized areas: 1950 and 1960." Census of Population: 1960 Supplementary Reports. 1961.
—. Selected Housing Characteristics: 2011 American Community Survey 1-Year Estimates.
http://factfinder2.census.gov/bkmk/table/1.0/en/ACS/ll_lYR/DP04 (accessed January 2, 2013).
—. State & County QuickFacts. http://quickfacts.census.gov/qfd/states/00000.html (accessed February 27, 2013).
—. United States Summary: 2000 Population and Housing Unit Counts.  2004.
—. "The urban and rural classifications." Geographic Areas Reference Manual.  1994.
U.S. Department of Agriculture. Summary Report: 2007 National Resources Inventory. 2009.
U.S. Department of Agriculture, U.S. Forest Service. National Report on Sustainable Forests—2010. 2011.
—. U.S. Forest Resource Facts and Historical Trends. 2009.
U.S. Department of Energy. 2011 Buildings Energy Data Book. 2012.
—. National Best Practices Manual for Building High Performance Schools. 2002.
U.S. Department of Transportation. National Transportation Statistics.  2012.
U.S. Energy Information Administration. Annual Energy Review 2010. 2011.
—. "Table HC10.1." 2009 Residential Energy Consumption Survey Data: Total Square Footage of U.S. Homes. 2012.
U.S. General Services Administration. The Benefits and Challenges of Green Roofs on Public and Commercial
Buildings. 2011. http://www.gsa.gov/portal/getMediaData?mediald=158783.
U.S. Geological Survey. Ground-Water Depeletion Across the Nation. 2003. http://pubs.usgs.gov/fs/fs-103-03.
—. National Assessment of Coastal Vulnerability to Sea-Level Rise, http://woodshole.er.usgs.gov/project-pages/cvi
(accessed April 3, 2013).
—. Water Use in the United States, http://water.usgs.gov/watuse (accessed November 1, 2012).
U.S. Global Change Research Program. Global Climate Change Impacts  in the United States. Cambridge University
Press. 2009. http://nca2009.globalchange.gov/download-report.
U.S. Government Accountability Office. Comprehensive Asset Management Has Potential to Help Utilities Better
Identify Needs and Plan Future Investments. 2004. http://www.gao.gov/products/GAO-04-461.

Works Cited
Vaccaro, J.J., and T.D. Olsen. Estimates of Ground-Water Recharge to the Yakima River Basin Aquifer System,
Washington, for Predevelopment and Current Land-Use and Land-Cover Conditions. U.S. Geological Survey. 2007.
Vicino, Thomas J. "The political history of a postwar suburban society revisited." History Compass 6, no. 1 (2008):
Vincent, Grayson K., and Victoria A. Velkoff. The Older Population of the United States: 2010 to 2050. U.S. Census
Bureau. 2010. http://www.census.gov/prod/2010pubs/p25-1138.pdf.
Walsh, Christopher J., Allison H. Roy, Jack W. Feminella, Peter D. Cottingham, Peter M. Groffman, and Raymond P.
Morgan II. "The urban stream syndrome: Current knowledge and the search for a cure." Journal of the North
American Benthological Society 24, no. 3 (2005): 706-723.
Wang, Sheng-Wei, Mohammed A. Majeed, Pei-Ling Chu, and Hui-Chih Lin. "Characterizing relationships between
personal exposures to VOCs and socioeconomic, demographic, behavioral variables." Atmospheric Environment 43,
no. 14 (2009): 2296-2302.
Wang, Youfa, and May A. Beydoun. "The obesity epidemic in the United States—gender, age, socioeconomic,
racial/ethnic, and geographic characteristics: A systematic review and meta-regression analysis." Epidemiologic
Reviews 29, no. 1 (2007): 6-28.
Wear, David N. Forecasts of County-Level Land Uses Under Three Future Scenarios: A Technical Document
Supporting the Forest Service 2010 RPA Assessment. U.S. Department of Agriculture, U.S.  Forest Service. 2011.
Wenger, Seth J., James T. Peterson, Mary C. Freeman, Byron J. Freeman, and D. David Homans. "Stream fish
occurrence in response to impervious cover, historic land use, and hydrogeomorphic factors." Canadian Journal of
Fisheries and Aquatic Sciences 65, no. 7 (2008):  1250-1264.
Weschler,  C.J. "Chemistry in indoor environments:  20 years of research." Indoor Air 21, no. 3 (2011): 205-218.
Weschler,  Charles J. "Changes in indoor pollutants since the 1950s." Atmospheric Environment 43, no. 1 (2009):
Wilcove, David S., David Rothstein, Jason Dubow, AM Phillips, and Elizabeth Losos. "Quantifying threats to imperiled
species in the United States." BioScience  48, no. 8 (1998): 607-615.
Woltemade, Christopher J.  "Impact of residential soil disturbance on infiltration rate and stormwater runoff."
Journal of the American Water Resources Association 46, no. 4 (2010): 700-711.
Xian, George, Collin Homer, Jon Dewitz, Joyce Fry, Nazmul Hossain, and James Wickham. "Change of impervious
surface area between 2001 and 2006 in the conterminous United States." Photogrammetric Engineering & Remote
Sensing 77, no. 8 (2011): 758-762.
Yip, Fuyuen Y., Jeffrey N. Pearcy, Paul L. Garbe, and Benedict I. Truman. "Unhealthy air quality—United States,
2006-2009." Morbidity and Mortality Weekly Report 60 (2011): 28-32.
Younger, Margalit, Heather R. Morrow-Almeida, Stephen M. Vindigni, and Andrew L. Dannenberg. "The built
environment, climate change, and health: Opportunities for co-benefits." American Journal of Preventive Medicine
35, no. 5 (2008):  517-526.
Yuan, Fei. "Urban growth monitoring and projection using remote sensing and geographic information systems: A
case study in the Twin Cities Metropolitan Area, Minnesota." Geocarto International 25, no. 3  (2010):  213-230.

                                                                                            Works Cited
Zogorski, John S., et al. Volatile Organic Compounds in the Nation's Ground Water and Drinking-Water Supply
Wells. U.S. Geological Survey. 2006. http://pubs.usgs.gov/fs/2006/3048.



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