Regional Traffic Signal Timing Optimization Methods For Urban Roads Under Oversaturated Traffic Conditions

Method of traffic signal timings optimization under oversaturated traffic conditions is the research emphasis in the field of current urban traffic management and control. Fousing on the faults and deficiencies of current methods on traffic signal timing optimization under oversaturated traffic conditions, a traffic signal timing optimization method is proposed for oversaturated traffic conditions in this paper, based on the characteristics of traffic demand transmission. By integrating the dynamic decomposition techinique for traffic singal control network, the regional traffic signal timing parameters are optimized.Based on the real-world traffic flow data that were collected at urban road segments and intersections, the temporal-spatial characteristics of traffic flow is analyzied, and the relevance and transmission characteristics of traffic demands are quantitatively described between intersections by applying the distance measure of dynamic time warping, to provide the basis to the study of traffic signal timing optimization method under oversaturated traffic conditions.For the study of real-time regional traffic signcal control network decomposition method, the procedure is proposed based on the idea to transmit traffic demands between intersections. Consequently, the approach to identify key intersection(s) and the approach to decompose the traffic signal control network are introduced in details. In the regard of identifying key intersection(s), the maximum possible traffic demand, calauted from the maximum traffic signal cycles and the maximum saturation degree, is treated as the traffic cpacity of the intersection, and then is used to identify the key intersections in the network. In the raegard of the regional traffic signal control network decomposion, the key intersection(s) is considered as the origin, and then the possible traffic demands that the upstream intersections could experienced are calculated based on the the relevance between intersections on the basis of demand transmission. Consequently, the set of the intersections can be obtained. In this sense, the proposed mthod realizes the dynamic decomposion of regional traffic signal control network under oversatuated traffic conditions.For the study of regional traffic signal timing optimization method, the optimization strategy is proposed, and then the method to optimize the traffic signal timings under oversaturated traffic conditions is presented. Based on optimized traffic capacity of the intersection in decomposing the traffic singal control network, the traffic singal timings, i.e., the cycle and green time, are optimized instead of the phases and the ratio of the green and the cycle. In terms of the performance measures of capacity, average delay and average queue length, the proposed optimization method is evaluated. The evaluation results show that the proposed method can effectively improve the intersection effiencicy.