Dynamic Signal Control Systems

Abstract

In the standard traffic assignment problem, link capacities are determined exogenously and remain unchanged throughout the solution process. Even though such an assumption may have been necessary in the past to keep a traffic assignment problem manageable, it fails to reflect the real situation. In fact, the magnitude of link capacities are dependent on the prevailing conditions consisting of physical features of the roadway and traffic conditions. Traffic conditions are strongly influenced by the roadway characteristics. During short periods of time, however, the traffic conditions are mostly influenced by the traffic signal control system of the roadway. Thus, link capacities can be simplified as functions of traffic signals for dynamic analysis. To better represent the real situation, the effect of signal controls on the traffic flow pattern must be explicitly taken into account in the standard traffic assignment.