vvEPA
United States
Environmental Protection
Agency
Air and Radiation
EPA420-S-98-006
July 1998
Office of Mobile Sources
TRAQTechnical Overview
Transportation Air Quality Center
Transportation Control Measures:
High Occupancy Vehicle Lanes
EPA's main strategy for addressing the contributions of motor vehicles
to our air quality problems has been to cut the tailpipe emissions for
every mile a vehicle travels. Air quality can also be improved by
changing the way motor vehicles are usedreducing total vehicle miles
traveled at the critical times and places, and reducing the use of highly
polluting operating modes. These alternative approaches, usually
termed Transportation Control Measures (TCMs), have an important
role as both mandatory and optional elements of state plans for
attaining the air quality goals specified in the Clean Air Act. TCMs
encompass a wide variety of goals and methods, from incentives for
increasing vehicle occupancy to shifts in the timing of commuting trips.
This document is one of a series that provides overviews of individual
TCM types, discussing their advantages, disadvantages, and the issues
involved in their implementation.
> Printed on Recycled Paper
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Hfijh Occupancy Vehicle IHQV) Lanes
Contents
O Background
ฉ Costs and Benefits
ฉ Implementation
O Keys to Success
ฉ Barriers
ฎ Equity Issues
ฉ Recent Examples
ฎ Sources
ฎ On-line Resource
High Occupancy Vehicle (HOV) lanes are intended to
maximize the person-carrying capacity of the roadway by
altering the design and/or operation of the facility to provide
priority treatment for HOVs. By providing two important
incentives - reduced travel time and improved trip time
reliability - HOV facilities encourage travelers to shift from
low occupancy vehicles to HOV use. This shift should reduce
vehicle trips, vehicle miles traveled (VMT), congestion, and
associated emissions from these activities. In several regions,
the scope of HOV facilities is being expanded to address
regional problems of suburban mobility, congestion, and air
quality.
HOV facilities have been implemented throughout the
United States. HOV lanes are typically open to buses and other
vehicles with a minimum of two or three occupants, although some are exclusive to buses. Many
types of HOV facilities exist. Some examples include:
** Separate roadways for exclusive HOV use
** Bypass lanes at metered freeway entrance ramps
** Lanes constructed within the freeway right-of way but physically separated
(e.g., by a concrete barrier) from the general-purpose freeway lanes and dedicated
for HOV use only
** Concurrent flow lane (i.e., a lane moving in the same direction of travel that is
not physically separated from the general-purpose traffic lanes)
** Contraflow lane (i.e., a lane in the off-peak direction of travel, typically the
innermost lane, designated for exclusive use by HOVs traveling in the peak
direction. This lane is separated from the off-peak direction general-purpose
travel lanes by some type of changeable demarcation, such as plastic posts or
pylons).
Other HOV facilities include queue bypass, bus streets, and bus tunnels. The most
common form of HOV facilities are concurrent flow HOV lanes followed by exclusive HOV
lanes in freeway rights-of-way. [1]
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High Occupancy Vehicle (HOV) Lanes Page 2
HOV facilities may involve adding entirely new capacity or reallocating existing capacity.
Along with a range of physical options, HOV facilities have operative options such as full-time
HOV-only use, peak time use, and reversing the direction of facilities during peak times.
1. Background
Although many HOV projects provide air
quality benefits, these projects may have
been implemented for reasons other than
air quality improvement.
Over the past 20 years, as
congestion has increased, HOV lanes
have become one of the most frequently
implemented TCMs. Although many
projects do provide some air quality
benefits, these projects may have been
implemented for reasons other than air
quality improvement. Increasingly, federal and state funding programs and regulations (such as
the CAAA, Congestion Management System requirements, and local traffic mitigation
ordinances) may place higher priority on including HOV facilities in state and regional
transportation system plans. [2]
HOV lanes have been shown to increase transit use and car occupancy for work-related
trips in congested urban travel corridors. The best HOV lanes now carry between 4,000 and
5,000 persons per hour, compared with around 2,000 for adjacent general purpose lanes. [3] The
most effective HOV lane improvements generally involve regional networks of linked lanes, with
a system of supporting facilities and services. Historically, the most successful HOV
applications have been along "radial" corridors into major central cities. Factors contributing to
success include the following:
*+ Population/employment densities
** Travel volumes
*+ Congestion levels
** Overall time savings
*+ Conditions at the destination area.
Little experience has been gained with HOV facilities in suburban and urban areas.
2. Costs and Benefits
HOV project costs vary greatly, depending on factors such as right-of-way acquisition or
the cost of land, bridge and overpass modifications, and interchange and ramp modifications. A
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High Occupancy Vehicle (HOV) Lanes Page 3
large portion of total costs often involves providing direct access to inside HOV lanes. Ramps
that allow buses to exit and enter a freeway to serve a transfer point are expensive, and time spent
getting on and off the freeway slows the trip. The Washington State Department of
Transportation (DOT) recently
completed a major study identifying HQV ^ on ^^ ^
projects needed to complete and wd, studied...tHOV im ts on air ,ity are
integrate their HOV Core system. , ,. , ,. ,
, ,,.,, , . . more complex and less studied.
The total bill for completion in 1995 L^^^^^^^^^^^^^^^^^^^^^^^^^^^^_
dollars was $1.25 billion, with an
additional cost of $377 million for
HOV Expressway access ramps. [3] A review of data obtained in the late 1980's from the
Institute of Transportation Engineers for 19 existing and 11 proposed projects showed costs
ranging from $4,000 to $24.5 million per lane mile. A concurrent flow priority lane located
within the existing highway right-of-way may cost between $30,000 and $2 million per lane mile
to implement while an exclusive right-of-way might easily exceed $8 million per lane mile. [4]
A recent quote from the Virginia DOT cites the 1-66 HOV lanes from Rt. 234 to Waples Mill Rd.
(11.5 miles) at total cost of $115,154,000 (this figure includes the construction of new sound
walls). The Right of Way cost alone was $5,117,000. [5]
HOV impacts on travel are fairly well studied. Different types of HOV facilities achieve
different amounts of time savings. The San Francisco Bay Area HOV Lanes Master Plan study
estimated a range of time savings from 1 minute to nearly 20 minutes. HOV impacts on air
quality are more complex and less studied. Nevertheless, researchers have derived emissions
impacts from the wealth of travel/traffic impact data. Los Angeles, San Francisco, Washington
DC, and Portland are some cities that have documented emissions impacts from their HOV
projects. Assessments of the effectiveness of HOV lane facilities in reducing system-wide
emissions have generally found reductions amounting to less than one percent. [4]
HOV lanes may reduce air pollution emissions by reducing running emissions and by
reducing trip-end emissions. Running emissions may be reduced because the increased use of
buses, vanpools, and carpools results in fewer vehicle miles traveled, and because of higher
speeds associated with uncongested operations in HOV lanes. If additional trips are not taken,
then HOV lanes will also reduce trip-end emissions. Trip-end emissions result from the initial
inefficient engine operation when the trip begins (cold start) and evaporation of fuel from a hot
engine at the end of the trip (hot soak). Cold starts and hot soaks occur for even short auto trips
and trip end emissions comprise the following:
*+ 75 percent of a 5-mile auto trip
*+ 61 percent of a 10-mile trip
** 45 percent of a 20-mile trip
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High Occupancy Vehicle (HOV) Lanes Page 4
If, however, users of HOV lanes meet their pool or bus through a park-and-ride
arrangement, these trip-end emissions may offset the reduced air emissions benefits. When
calculating effectiveness of HOV lanes in reducing emissions, one must account for trip-end
emissions resulting from the use of linkages.
3. Implementation
HOV lanes are typically implemented by a state DOT due to their substantial physical and
financial requirements. HOV lanes typically require three to eight years for planning, design, and
construction. Although HOV
facilities are generally public works
facilities, the potential exists for
private or non-profit authorities to
construct and operate these facilities
along the lines of a toll road (these
are also called "High Occupancy
Toll" or HOT lanes). Operators
may use discriminatory pricing
strategies such as granting toll discounts to HO Vs. There are no known instances in which HOV
facilities have been built or operated by individual employers or developers, but the potential
exists for these private initiatives (e.g., operating exclusive ramps or interchanges).
There are no known instances in which HOV
facilities have been built or operated by
individual employers or developers, but the
potential exists for these private initiatives (e.g.,
operating exclusive ramps or interchanges).
4. Keys to Success
HOV facilities pose low risks compared to other fixed transit improvements and provide
flexibility in that they allow for staged implementation. Operators may start with modest
minimum occupancy requirements that can be adjusted over time to provide the appropriate
balance between efficiency and utilization. If an HOV lane is not sufficiently utilized, it may be
converted to other uses such as mixed-flow operation or emergency shoulders.
Many HOV projects have used education and marketing tools to:
** Advertise the opening of HOV lanes
** Educate drivers in the use of HOV lanes
** Promote immediate use of HOV lanes
** Create awareness of support facilities
** Provide updated accounts of HOV lane time savings and usage
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High Occupancy Vehicle (HOV) Lanes Page 5
HOV lanes can be more effective if implemented along with transit improvements or
rideshare incentives. [6] One of the most critical components of implementing a successful HOV
program is enforcement. Surveys show that early and substantial enforcement of HOV rules on a
new facility is the best determinant of long-term public compliance. For example, projects that
allow police to pull violators over without impeding the flow of HOV lanes, along with suitably
structured system of fines, have proven successful. [4]
5. Barriers to Implementation
The potential need to acquire land to implement the HOV lanes often determines the
facility's feasibility and the time required to implement the project. Further, HOV project
planning and design involves various agencies and interest groups, including political leaders,
business groups, and citizen groups.
6. Equity Issues
HOV facilities generally provide the most benefit to commuters whose travel occurs
during weekday peak periods. The distribution of costs and benefits depends on an area's
situation. If existing capacity is redistributed, those who rely on mass transit and are able to join
carpools and vanpools will receive time-savings benefits and potential financial benefits (e.g.,
employers may provide HOV
parking subsidies). These HOV
facilities may benefit low-income
travelers while imposing costs upon
high- income travelers. For example,
mass transit riders tend to be from
lower income groups and value time
One of the most critical components of
implementing a successful HOV program is
enforcement. Surveys show that early and
substantial enforcement of HOV rules on a
new facility is the best determinant of long-
, ,, u u term public compliance.
savings less than high-income v v
individuals. Travelers who lack
access to transit services or are
unable to join carpools and vanpools, and thus must drive alone, will not benefit from the
increased time savings provided by HOV facilities.
If additional capacity is provided, all travelers should benefit from the reduced congestion
and increased time savings. The value of these benefits depends on how travelers value their
time. Adding capacity will impose land use impacts upon those in the surrounding area. These
impacts may be offset, however, from the benefits received from reduced congestion and
improved air quality.
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High Occupancy Vehicle (HOV) Lanes Page 6
7. Summary of Recent Examples
If we include HOV projects beyond freeways
and separate right-of-ways, HOV lanes
become the second most frequently
implemented TCM, following traffic flow
improvements.
As of 1992, some 49 freeway
or separate right-of-way HOV projects
were operating in North America in 22
metropolitan areas. These projects
occur in major metropolitan areas
across the U.S. (e.g., Los Angeles,
Denver, Houston, Chicago, New
York, Washington D.C., and Miami).
Most of these HOV facilities are oriented to serve the major downtown core of a metropolitan
area along radial corridors. These facilities usually are in operation during the peak morning and
afternoon periods and primarily serve the downtown oriented work trip. Some other examples of
successful projects include Minneapolis 1-394, Hampton Roads 1-64, Seattle 1-5, and the San
Francisco/Oakland Bay Bridge. If we include HOV projects beyond freeways and separate right-
of-ways, HOV lanes become the second most frequently implemented TCM, following traffic
flow improvements. [5]
HOV lanes are generally more effective when paired with other measures such as park-
and-ride lots, employer-based transportation (vanpool and car pool) programs, and commuter
parking subsidies. For example, William M. Mercer in Seattle provides its employees HOV
parking discounts and preferential HOV parking treatment. Hewlett Packard in Palo Alto also
combines TCM strategies by providing its employees with ridematching services, transit
information, and preferential HOV parking treatment, including reserved spaces.
8. Sources
[1] Synthesis of Travel Demand Management Findings: Inventory of Measures and Synthesis of
Experience Final Report, Report No. DOT-T-94-12, U.S. Department of Transportation,
Washington, D.C. (September 1993).
[2] Knapp, Keith K., Rao, K.S., Crawford, Jason A., and Krammes, Raymond A. The Use and
Evaluation of Transportation Control Measures, Research Report 1279-6 Research Study Title:
Air Pollution Implications of Urban Transportation Investment Decisions, Texas Department of
Transportation in cooperation with the U.S. Department of Transportation Federal High way
Administration, College Station, TX (September 1994).
[3] Public Interest Transit Forum Homepage, Washington State (http://www/gt-wa.com/rta).
[4] Transportation Control measure Information Documents, Cambridge Systematics, Inc., U.S.
Environmental Protection Agency, Washington, D.C. (March 1992).
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High Occupancy Vehicle (HOV) Lanes Page 7
[5] Personal Communication with Virginia DOT (February 4, 1997).
[6] Turnbull, Katherine F., High Occupancy Vehicle Project Case Studies Historical Trends and
Project Experiences., Report No. DOT-T-94-18, U.S. Department of Transportation, Washington,
D.C. (August 1992).
9. On-Line Resource
The Environmental Protection Agency's Office of Mobile Sources has established the
TCM Program Information Directory to provide commuters, the transportation industry, state and
local governments, and the public with information about TCM programs that are now operating
across the country. This document and additional information on other TCMs and TCM
programs implemented nationwide can be found at:
http://www.epa.gov/omswww/transp/traqtcms.htm
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