Freeway Surveillance and Control in Chicago Area

The Chicago area expressway network features the world's first and largest freeway traffic surveillance and control system. From pioneer experiments with detector/telemetry/computer monitoring of traffic flow, and the development of entrance ramp metering, the real-time system now covers 110 miles (177 km), with 1,600 detector locations and 70 controlled ramps, all centrally supervised. This paper describes the surveillance and control system and its basic components, discusses the implementation and operational experience to date, and relates the use of electronic traffic aids to overall urban freeway traffic management efforts. The Chicago area case study demonstrates successful progress towards reducing congestion, improving flows, increasing safety, conserving energy, expediting emergency responses, and providing motorist aid and imformation.