Experiences with Adaptive Signal Control in Germany

Abstract

Germany has a long tradition of traffic-actuated and -coordinated signal control. In recent years a specific approach to traffic actuation called a model-based system, or adaptive control, has found its way into practice. In the city of Muenster, Germany, the coordinated signal control system on the 6-km-long arterial Albersloher Weg, with 24 signalized intersections, has been completely renewed in a three-step process involving the old system, a rule-based traffic-actuation system, and an adaptive system. An empirical evaluation of this process by a university research team showed that conventional actuated signal control improved traffic performance in the first step. Additional significant improvement (as much as 30%) in traffic flow performance could be achieved by implementing Motion, an adaptive signal control system. However, further developments are required to meet the expectations of city engineers and road users. In particular, switching between optimized signal plans, which is an essential feature of the Motion system, must be improved.