2001 Volume 14 Issue 12 Pages 601-609
The coordinated traffic signal control parameters are characterized by cycle length, split and offset. These parameters should be carefully calibrated so that the total performance index is optimized. Our scope of opitimization is called sun-area, which is defined by a series of intersections. The conventional methods may be deficient in that each parameter is calculated individually and the overall traffic index is not considered. This paper describes a new method of determining coordinated control parameters simultaneously. Since it is difficult to express the delay time as a function of the offset parameter, the procedure is divided into two parts. In the first step, the cycle length and the split are obtained by minimizing the total traffic delay. The optimal offset is calculated so as to maximize the bandwidth, which is the fraction of time during which vehicles may pass through all the intersections without stopping in the sub-area. In the second step, we estimate the total queue length in the sub-area by using a microscopic traffic flow simulator. By integrating these two steps, several control planes are obtained, and the best solution is chosen among them.