Partition Of Long Urban Arterials Under Signal Coordination Control

With the growth of our country's economy and the improvement of people's living standard, traffic congestion has become one of the major problems in many metropolitan areas. Improving the traffic signal control at urban intersections is an effective way to relieve traffic congestion. Signal coordination is to simultaneously optimize the timings of grouped signals to improve the traffic propagation along the whole urban arterials. Signal coordination is currently widely implemented in urban traffic control.Existing signal coordination methods mainly focus on arterials with limited number of intersections, e.g.,5-6 intersections, while, currently many urban arterials may contain ten or more intersections in many cities due to urban sprawl. If coordination is performed for all the intersections at the same time, the green bandwidths generated may be very small, and sometimes two-way bandwidths may not be achievable. Therefore, it is necessary to divide a very long arterial into several small subsystems, and then conduct signal coordination for each subsystem individually to improve the performance of the whole arterial. This is cal1ed System Partition.Traditional system partition methods of urban arterial either builds highly empirical partitioning indexes or uses heuristic methods to search for the partitioning plans. Since these methods can hardly obtain the optimal partitioning plan, therefore, they are very difficult to guarantee the ideal coordination performance of the whole arterial. This thesis proposes a system partition model with two different objective functions to improve the signal coordination control for large-scale urban arterials, based on the classical MAXBAND methodology. This model is constructed by introducing multiple sets of binary variables, and by building constraints on coordination control efficiency, common cycle length as well as the number of signals in each subsystem. Then, Genetic Algorithm (GA) is applied to solve this model which is a mixed-integer nonlinear programming problem. A case study with three demand scenarios using CORSIM simulation is carried out to verify the feasibility and validity of the proposed model.The optimization and simulation results show that generally the green bandwidths will increase and the average stop ratio of through vehicles will decrease in each subsystem, when the number of subsystems increases. However, the improvement of the stop ratio of through vehicles for the whole arterial is not achieved due to that platoons will be frequently interrupted by more breaking points. Different objective functions are employed in the proposed model, which lead to similar performance measures such as travel delay and average stop ratio. Compared with Synchro, the partitioning plans generated by the proposed model can improve the average bandwidth of all subsystems significantly and also outperform those Synchro plans in terms of average delay and average stop ratio. The proposed model is proved to be of potential.In sum, the work present in this thesis provides a theoretical basis for further research of system partition, and a method suitable for field engineering application.