Optimal signal timing for an oversaturated intersection

Traffic congestion occurs frequently at downtown intersections during rush hours, at road construction zones as well as at accident sites. Under such circumstances, traffic flow exceeds intersection capacity causing queuing of automobiles that cannot be eliminated in one signal cycle. In this paper, we present a timing decision methodology which considers the whole oversaturation period. Discrete dynamic optimization models are developed and an algorithm to solve them is presented. The optimal cycle length and the optimal assigned green time for each approach are determined for the case of two-phase control. The application of the performance index model to certain multi-phase signals in common use is also introduced. Evaluation results indicate that the proposed discrete type performance index model is a more appropriate design for congested traffic signal timing control.