Strategies for Practical Expressway Control

A practical approach to the problem of expressway control is described. The method deals specifically with the first level control of individual bottlenecks. A simple risk function, based on easily measured traffic variables, is used as the control parameter. The control handles the dynamic fluctuations in traffic flow observed in the typical traffic stream and allows for varied operating conditions. It includes provision for traffic incidents. The method is compared to the other approaches to expressway control which are briefly reviewed. The issue of overall system control for a corridor is described but the control method does not attack this directly.