Adaptive Dynamic Control for Road Traffic Signals

Control of road traffic by signals requires timings for the stages during which signal indications remain constant. Approaches to calculation of these durations include traffic-responsive strategies as well as fixed-time ones. In all cases, these control methods require some parameters that will ultimately depend on traffic flows. The present paper introduces an adaptive method for responsive control that adjusts the stage durations according to traffic flows. The methodology used for this is approximate dynamic programming, which uses a state-dependent estimate of future optimised costs to assess decisions. Results are presented for example applications, showing favourable performance by comparison with other approaches.