A 1991 study by the Texas Transportation Institute for the Federal Highway Administration concluded that the Los Angeles metropolitan area experiences by far the worst congestion in the United States. As part of the response to this problem, the City of Los Angeles has developed the Automated Traffic Surveillance and Control (ATSAC) system. A project undertaken by the City's Department of Transportation (DOT), ATSAC is a computerized traffic monitoring and control system that dramatically improves upon traditional traffic management systems. Local studies have shown improved traffic management and considerably reduced travel times, congestion delays, air emissions, and fuel consumption in the city. Between its original conception in 1979 and implementation in 1992 at 800 intersections across L.A., the ATSAC has proven to be an important and innovative traffic management tool.
The ATSAC program has several key features that distinguish it from conventional or other traffic management systems. It has traffic adaptive signal timing to adjust signals based on road traffic and help smooth the flow of city traffic. It is able to detect road incidents or tie-ups and alert emergency or repair vehicles for dispatch. While according signal priority to light rail transit vehicles, it is capable of detecting system malfunctions continually so that repairs can be made instantly. With closed-circuit video monitoring and real-time relay of traffic information, the system seeks to continuously identify traffic congestion levels and incidents. Compared with other computer-controlled signal systems, ATSAC has the most extensive use of roadway detectors and computation of traffic flow measures to evaluate its own performance.
The DOT plans to eventually cover all 4000 signalized intersections in Los Angeles. Several developments to the system are also underway. L.A. DOT has played a critical role in integrating ATSAC with the Smart Corridor Demonstration Project, which will soon link traffic controls on the Santa Monica Freeway with ATSAC control of five principal streets in Los Angeles alongside three adjacent cities. A major emphasis of this joint, intergovernmental effort is the distribution of traffic information to the public through a variety of media such as highway advisory radio, changeable message signs and cable TV. Moreover, the DOT is enhancing ATSAC to provide signal priority to buses as well as light rail transit vehicles, increase video surveillance and provide more information to travelers. The ATSAC has an open system design, which is capable of accepting technical enhancements anytime.
To date, the DOT has done a remarkable job of helping replicate the system elsewhere with similar systems already functioning in several cities throughout the U.S. including Portland, Honolulu and Pasadena. The DOT staff has been quite generous in this process by giving ATSAC demonstrations to over 3000 visitors from United States and 35 other countries. By insisting on an open-ended, non-proprietary system, the DOT has allowed effective dissemination of ATSAC.