Group-based optimization of a time-dependent TRANSYT traffic model for area traffic control

In this paper, a time-dependent TRANSYT traffic model is developed for the evaluation of a performance index, which is a weighted combination of the estimated delay and number of stops. The group-based specification of signal timings is employed for the traffic model and the set of constraints on these variables is formed. The derivatives of the performance index with respect to the group-based variables are derived, based on which optimization heuristics are developed to solve the time-dependent problem. A medium size signal-controlled network from the Shatin New Town in Hong Kong is employed as a numerical example to illustrate the effectiveness of the heuristics. Two other scenarios are also analyzed, one is based on the average traffic flow and the other takes the traffic flows in individual time intervals for independent analyses. A well-known microscopic simulation model NETSIM is used to evaluate the performance indices for the signal plans derived from these three scenarios. With the proposed heuristics, a remarkable improvement over the average flow scenario is obtained, and when compared with the signal plans from independent analyses, a good improvement is also found. Sensitivity analyses are conducted to illustrate the superiority of the proposed methodology under different levels of congestion in the network.