Knowledge Resources

The U.S. Department of Transportation study "What Have We Learned About ITS?" is a synthesis of the national experience with implementing ITS through the year 2000, with a goal of more effectively planning the future of the National ITS Program. This synthesis examines which ITS technologies and applications have been successful, which have not, and those for which more information is needed to make a judgment. The seven areas included within the scope of this study are as follows:

• Freeway, Incident, and Emergency Management, and Electronic Toll Collection (ETC)

• Arterial Management

• Traveler Information Systems

• Advanced Public Transportation Systems

• Commercial Vehicle Operations (CVO)

• Cross-Cutting Technical Issues

• Cross-Cutting Institutional Issues

Adaptive signal control systems use algorithms that perform real-time optimization of traffic signals based on current traffic conditions, demand, and system capacity. Adaptive control software adjusts traffic signal splits, offsets, phase lengths, and phase sequences to minimize delay and reduce the number of stops. The extent of benefits depends on several factors including the number and spacing of intersections, the size of study area, demand patterns, levels of nonrecurring congestion, and the type of adaptive control.

Adaptive signal control systems improve coordination and reduce the number of stops, which decreases the rear-end crash rate. In Los Angeles, Broward County, and Oakland County adaptive signal control reduced the number of stops by 28 to 41 percent .