The Advanced Distributed Ramp Metering System (ARMS): (Extended Abstract) *

Ramp metering is an important technique to efec- tively utilize the freeway capacity by regulating the traf- fic flow of freeway entrance ramps. In this extended abstract, we discuss the outline of the free flow control algorithm of the Advanced distributed -Ramp Metering System, ARMS, for the real-time control of freeway ramp metering systems (4). ARMS consists of three levels of control algorithms integrated together for free flow control, breakdown prediction, and congestion resolution. Based on a free flow trafic model, the free flow control algorithm takes into account of the congestion risk when it tries to maximize the trafic throughput. The breakdown prediction algorithm can make prediction on the possibility of imminent conges- tion caused by flow breakdown, and the congestion res- olution algorithm is to resolve the congestion if it actu- ally occurs. The ARMS has a modular architecture so that it can be scaled for incremental implementation. To control freewag trafic, a system wide optimization objective is first defined for a target area. Then, ramp metering decisions are made by the entrance ramp con- trollers within the target area after their tra& data are exchanged.