Urban Traffic Signal Coordination Control Based On Sub-Area Dynamic Division

As an important way to relieve urban traffic pressure and improve the operational efficiency of the road network, traffic signal control has aroused extensive attention of scholars at home and abroad. However, transportation system is a complex system which has strong correlation and high randomness. So for urban traffic control system, it is an enormous challenge to assign the right of way to every vehicle scientifically and reasonably.After summarizing the research in the field of urban traffic signal control and analyzing advantages and disadvantages of existing signal control methods, original control optimization algorithms are improved. In accordance with the ascending order of the control range, this paper develops the research work about the traffic signal control system, including following three aspects:Firstly, a single intersection intelligent control method based on traffic demand is proposed. According to statistical information of the intersection’s daily traffic demand in different stages, the vehicle arrival rate of each lane group based on historical data is calculated. Then control phase sequences are selected to improve the utilization rate of the green time. At the same time, the initial green time of each phase is determined. In order to make the algorithm a certain self-adaptive to the change of the traffic environment, the online adjustment of the green time is made when detecting vehicle arrival in each phase. Finally, the feasibility and advantages of the proposed method in the case of different traffic demand are verified by micro-simulation software.Secondly, an arterial intelligent coordination control method based on the bandwidth maximization model is proposed. To let intersections on the artery have a certain ability to operate independently, a two-level control structure is used. The upper-level coordination layer is mainly responsible for making a choice about phase sequences, determining the green ratio and generating control scheme based on the variable bandwidth optimization model; each intersection is designed as a lower-level control layer, implementing control strategies as well as correcting the actual green time appropriately according to the vehicle detector. Thus the width of the band is increased to reduce number of stops. Simulation results show that the proposed method is slightly better than the traditional bandwidth maximization control, improving the overall performance of the artery greatly.Thirdly, an area green wave intelligent coordination control method based on the sub-area dynamic division is proposed. The system adopts a three-level distributed control structure, combining sub-area dynamic division and the appropriate maximum bandwidth optimization method automatic selection on the basis of the type of sub-area with the function that independent online fine-tuning of the green time in each intersection. Particularly, multiple indexes and dividing twice are introduced in the sub-area dynamic division so as to partition the load network more scientifically and effectively. First of all, composite index which is based on distance, traffic volume and cycle three main principles is employed to accomplish the rough division. So those links that need to be coordinated or not are identified after this step. For the purpose of overcoming the shortcomings of existing methods which can not guarantee the coordination control effect of the sub-area beforehand, the bandwidth attainability index is introduced. In the light of the descending order of the rest rough divisional index, the fine division is carried on using the attainability index. And the online adjustment procedure of the sub-area is also proposed, which is based on the bandwidth attainability index and the "Adjusting Index". At last, the road network in Hangzhou City is selected as a case study to test the control effect of the proposed system. Through comparative analysis, the results indicate that the system can improve the transport capacity of the road network significantly and the new sub-area dynamic division method is stable and effective.