vvEPA
United States
Environmental Protection
Agency
Air and Radiation
EPA420-S-98-007
July 1998
Office of Mobile Sources
TRAQTechnical Overview
Transportation Air Quality Center
Transportation Control Measures:
Intelligent Transportation Systems
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 used—reducing 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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Intelligent Transportation Systems
Contents
O Background
@ Costs and Benefits
© Implementation
O Keys to Success
© Recent Examples
© Sources
O On-line Resource
Intelligent transportation systems (ITS), provide a
technological solution to the problem of growing congestion
on U.S. roadways. The U.S. Department of Transportation
(DOT) has defined an ITS infrastructure consisting of traffic
detection and monitoring, communications, and control systems
required to support a variety of ITS products and services in
metropolitan and rural areas. Whether infrastructure is deployed
by the public sector, the private sector, or a combination of the
two, depends on the locality. The following are types of systems
that can be employed as part of an ITS:
Traffic signal control systems, which have the capability to adjust the amount of
green light time for each street and coordinate operation between each signal to
maximize the person and vehicular throughput
Freeway management systems, which provide for control of traffic entering the
freeway, as well as coordination of response to emergency and special-event
situations
Transit management systems, which include hardware/software components on
buses, dispatching centers, radio communications, operator training, and
maintenance to increase mass transit ridership and productivity
Incident management programs, which help to quickly identify and remove
incidents (e.g., accidents and stalled vehicles) that occur on area freeways and
major arterials
Electronic toll collection systems, which include hardware and software for
roadside and in-vehicle use and driver payment cards to allow drivers to pay tolls
without stopping, thus decreasing delays and improving toll collection
productivity
Multimodal traveler information systems, which serve as a repository for
current, comprehensive, and accurate traffic flow data and disseminate this
information to travelers through a variety of methods
Highway/railroad crossings and interface systems, where traffic signals are
coordinated with train movements and drivers are notified of approaching trains
through in-vehicle warning systems
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**• Emergency management systems, where response personnel are linked to
incident management centers to ensure that the closest available applicable
emergency response unit can respond to an incident
The rationale for installing technological solutions rather than traditional highway
expansion varies with location and project type. Freeway management systems are a cost-
effective way to increase throughput where additional lanes requiring expanded right-of-way
would be very expensive or politically impossible. Some transit operations are implementing
ITS as the best way to improve passenger convenience and security. The way an area chooses to
use ITS technologies in meeting transportation needs can either increase or decrease its air
quality.
In the short run, using ITS technologies to increase speeds and capacity on severely
congested highways can reduce emissions of some pollutants. This beneficial effect results from
more efficient engine operation at steady speeds rather than stop-and-go traffic at very low
speeds. However, there is a point at which higher speeds cause pollutant emissions to increase
again. Moreover, as the increased capacity encourages more driving, the impact of increased
road capacity and higher traffic volumes on air quality is clearly negative.
Sustainable uses of ITS technologies can reduce congestion without encouraging more
traffic for example, by electronic tolling and better management of traffic flow. Beginning to
implement sustainable ITS strategies now can give a locality a head start in achieving and
maintaining healthy air. Sustainable ITS involve environmental design goals which both
increase the flow of traffic and decrease the number of single occupancy vehicles. Localities that
implement sustainable ITS may find conformity demonstrations easier or may take credit for
sustainable ITS measures in their air quality plans. Choosing "win-win" ITS measures that both
improve transportation system efficiency and air quality can maximize return on transportation
investments. In areas where operating costs are affected, life-cycle cost comparisons by the
operating authority can justify ITS.
1. Background
ITS user services have been developing
over the past three decades. Transportation
authorities have been installing progressively
more flexible traffic signal systems since the first
computerized systems were commissioned in the
early 1960s. Isolated ramp meters have
developed into freeway management systems in metropolitan areas such as Los Angeles,
Houston, San Antonio, and Seattle. Other cities such as Detroit and Atlanta are building or
expanding traffic management centers that include freeway management components. Incident
ITS computerized traffic signal
systems have been in place since the
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Page 3
management programs that began as courtesy patrols and CB monitoring have incorporated new
technologies and are increasingly being integrated into transportation management centers.
Technologies incorporated include motorist call boxes, cellular phone call-in, loop detectors, live
video, and, more recently, microwave, ultrasonic, and image processing techniques.
Transit fleet management has also evolved from managers with radios and clipboards to
dispatch centers receiving real-time Automatic Vehicle Location information derived from sign-
post or Global Positioning System equipment. Electronic fare payment is expanding from
magnetic strip farecards in use in the Washington, D.C. METRO and San Francisco BART rail
systems to systems that accept multi-purpose magnetic strip cards, commercial credit cards, and
remote electronic transaction devices. Electronic toll collection systems are being installed both
in urban areas and on rural tollways.
2. Costs and Benefits
The benefits of ITS are derived from a
smoother traffic flow with less delay from
signals, incidents, and traffic queues. Most
aspects of the ITS infrastructure contribute to
time savings. Other benefits include emissions
reduction, accident reduction, improved transit
customer service, increased roadway capacity and
speed, and decreased fuel consumption. [1] The
total costs are dependent on the size of the
system and the types of technology used. ITS
systems could be implemented independently,
but concurrent implementation is expected to significantly increase overall benefits and decrease
incremental costs.
ITS Costs Include:
M> System design
^ Procurement
**• Deployment of the system
>•* System operation and maintenance
>•*• Evaluation and support
>•* Public outreach
3. Implementation
An ITS requires a substantial investment of government resources. The measure is
typically implemented by the public sector, but private sector participation is highly encouraged,
particularly in the collection and dissemination of traveler information. ITS systems can be
readily deployed in the near term and are typically eligible for federal funding.
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4. Keys to Success
To be effective, the implementation of all features of an ITS must be carefully
coordinated. Key components needed for the success of the system include the following:
^ Capability to distribute multimodal traveler information to the general traveling
public
**• Surveillance and detection capability, resulting in timely, comprehensive, and
accurate information on traffic and transit system performance
^ Infrastructure-based communications systems linking field equipment with central
software/database systems
**• Communications (routine information sharing) among jurisdictions, between
traffic and transit agencies, and between the public and private sectors, without
necessarily relinquishing control responsibility
**• Information sharing/coordination with emergency medical services, hazardous
materials programs, and other appropriate participants
^ Proactive management of roadway and transit resources to achieve metropolitan
transportation objectives
**• Sufficient resources for continuing support of system operations and maintenance
needs, including personnel and training requirements
Many ITS services require wide-scale coordination across jurisdictional boundaries.
5. Summary of Recent Examples
ITS are being implemented widely across the nation. Transit management systems are
currently operating in 24 U.S. metropolitan areas, with another 31 areas in various stages of
procurement. Twelve authorities are currently using electronic toll collection. Recent studies
have shown these programs to be successful at reducing emissions, as well as providing other
benefits. [1]
The City of Abilene, for example, installed a synchronized traffic signal system. A
portion of the funding for the Abilene upgrade came from a bond issue that specifically included
the upgrade and the remainder came through a state-funded program. The system upgrade was
partly to move traffic better and partly to replace an antiquated system that was causing difficulty
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in locating replacement parts. The portion of funding on the bond issue competed with other
projects in the public works budget for priority. The City of Abilene reported the overall impacts
shown in Table 1.
Table 1 - Results from Abilene Signal System Upgrade
Travel time
Travel speed
Number of stops
Delay
Fuel consumption
CO Emissions
HC Emissions
NOX Emissions
-14%
+22%
+0.3%
-37%
-6%
-13%
-10%
+4%
6. Sources
[1] Federal Highway Administration. Intelligent Transportation Infrastructure Benefits:
Expected and Experienced. Prepared by The MITRE Corporation. Washington, D.C. (January
1996).
7. An On-line Resource
The Environmental Protection Agency's Office of Mobile Sources has established the
Transportation Control Measure (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 can be found at:
http://www.epa.gov/omswww/transp/traqtcms.htm
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