The Research On Combinatorial Optimization Of Intersection Control Method Based On Variable Approach Lane And Signal Timing Optimization

With the rapid development of our social economy,the process of urbanization has been accelerating.Due to the lack of scientific and systematic urban planning in the early development of the city,many large cities and megacities in China have been expanded to the periphery of the downtown area,resulting in urban space structure expands like standing pancake.In this context,many cities are showing “ring + radial” road network structure,which led to various types of traffic problems,especially the tidal discharge caused by commuting traffic is the most serious.In order to alleviate the urban traffic congestion,one is to develop the public transportation and increase the public transit split rate.The other is to strengthen the management and control of urban traffic and improve the capacity and efficiency of road network.The intersection is the bottleneck of urban traffic network and the source of traffic congestion.Therefore,traffic management and control should focus on the optimization of traffic management and organization at intersections.The management and optimization methods of intersections mainly include two aspects,one is time optimization and the other is spatial optimization.Time optimization is mainly for oversaturated intersection,according to the actual conditions of the intersection and traffic flow characteristics,the signal intersections of the arterial and the entire road network can be further optimized to achieve the global optimal of the whole road network.Spatial optimization mainly focuses on the physical space of the intersection,such as waiting areas,import channelization and so on,improving the capacity of the intersections from the space.In this paper,the intersections with the characteristics of unbalanced traffic flow distribution are chose as the research object,from the two-dimensional perspective of space and time.This paper puts forward the idea of combinatorial optimization of intersections,and focuses on solving the traffic congestion caused by sudden increase of left-turn traffic volume in a short period.In the spatial optimization,a method is proposes to set up variable approach lane at the entrance of the intersection,and the real-time function of variable approach lane is determined according to the real-time traffic flow data so as to realize the adaptive control of the variable approach lane.The time optimization is based on the setting of variable approach lane.According to the result of the spatial optimization,the signal timing dynamic optimization of the intersection is further improved,to minimize the average delay of the intersection of the car.The combinatorial optimization system consists of three parts: traffic state predicting subsystem,VAL decision-making subsystem and signal optimization subsystem.In this paper,the coordination control mechanism of these three subsystems is explained,and then the structure of three subsystems and the model algorithm are studied respectively.Finally,the paper demonstrates the implementation process of combinatorial optimization,and analyzes the vehicle delay and service level at the intersection before and after the combinatorial optimization.The results show that this method is more efficient than the single lane function optimization and signal-timing optimization,the level of service at the intersection is upgraded from E to D level.