The advanced distributed ramp metering system (ARMS)

Ramp metering is an important technique to effectively utilize the freeway capacity by regulating the traffic 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. ARMS consists of three levels of control algorithms integrated together for free flow control, breakdown prediction, and congestion resolution. Based on a free flow traffic model, the free flow control algorithm takes into account of the congestion risk when it tries to maximize the traffic throughput. The breakdown prediction algorithm can make prediction on the possibility of imminent congestion caused by flow breakdown, and the congestion resolution algorithm is to resolve the congestion if it actually occurs. The ARMS has a modular architecture so that it can be scaled for incremental implementation. To control freeway traffic, a system wide optimization objective is first defined for a target area. Then, ramp metering decisions are made by the entrance ramp controllers within the target area after their traffic data are exchanged