Based on the sucessful system test during the 1984 Los Angeles Olympic games, ATSAC is a method for optimizing the existing highway and arterial street system. It is a computer-based traffic signal control system that monitors traffic conditions and system performance, selects appropriate signal timing (control) strategies, and performs equipment diagnostics and alert functions. Sensors in the street detect the passage of vehicles, vehicle speed, and the level of congestion. This information is received on a second-by-second (real-time) basis and is analyzed on a minute-by-minute basis at the ATSAC Operations Center, to determine if better traffic flow can be achieved by changing the signal timing. If required, the signal timing is either automatically changed by the ATSAC computers or manually changed by the operator using communication lines that connect the ATSAC Center with each traffic signal. To supplement the information from electronic detectors, closed-circuit television (CCTV) surveillance equipment is installed at critical locations throughout the City. The major benefit of the ATSAC System is the ability to effectively manage dynamic traffic flow. Evaluation studies of the ATSAC System show that travel times, traffic signal delay, vehicular stops, air emissions and fuel use are significantly reduced.