STREAM (STRATEGIC REALTIME CONTROL FOR MEGALOPOLIS-TRAFFIC) ADVANCED TRAFFIC CONTROL SYSTEM OF TOKYO METROPOLITAN POLICE DEPARTMENT

The Advanced Traffic Control System of Tokyo Metropolitan Police Department--a system designed to handle traffic control in the 21st century--was operable in February 1995. As part of this system, a new signal control system called STREAM (Strategic Realtime Control for Megalopolis-Traffic) was designed, which aimed to alleviate traffic congestion, distribute traffic, and reduce the number of traffic accidents. STREAM is applicable for all traffic conditions, from undersaturation to oversaturation, and the concept of control is as follows: 1) to form safe traffic flow in case of light traffic; 2) to maximize traffic capacity and alleviate congestion in case of near-saturation by improving efficiency of the green time; and 3) to carry out preference control over conflicting traffic flow in case of oversaturation. Congestion Alleviation Control (CAC), which is the main function of STREAM, was operating 308 critical intersections within Tokyo in February 1995. The results of adoption of CAC show that on major roads (1,515 km) the total travel time has been reduced by 9 percent and the congestion length-time has been reduced by 28 percent. This translates into an economic saving of over 100 billion yen per year. In this paper, the authors discuss the concept of control, the system configuration, traffic information processing, the control methods and the results obtained from introducing STREAM.