Area Signal Control In Oversaturated Urban Traffic Network Optimization

Due to China's rapid economic growth in recent years,the rapid growth of private car owner has resulted in frequent occurrence of urban traffic congestion,especially in cities.At the same time,new theories and methods have been applied to traffic signal control to solve traffic congestion problems in cities.At present,the achievements of traffic signal control methods are all studied and optimized on the basis of traffic unsaturated state,so the research on oversaturated traffic signal control still has defects.Under the current research background of traffic network problems,the thesis mainly focuses on the optimization of network signal control under supersaturation.The main research results are summarized as follows:(1)division of signal control sub-areas in urban road traffic network areaDynamic division of signal control sub-regions in supersaturated state is the premise of signal timing optimization.The method of dividing signal control sub-regions in this paper is to establish a directed graph of road network by taking intersections as the vertices of the network,the sections connecting adjacent intersections as directed edges,and the impedance(time,distance)of the sections as the weights of the edges.The corresponding algebraic representation of network directed graph is established,and the idea of network node accessibility is used to divide the network into traffic control subareas.(2)regional raffic state consistent signal control methodA general definition of state consistency is given,which combines signal control with traffic state consistency to control traffic state on the road network.Aiming at the phenomenon of over-saturation of network traffic,according to the principle of traffic flow conservation in time and space in the network,taking the input volume and release ratio of boundary sections as research objects,considering the traffic volume of upstream and downstream sections,a spatial model of traffic signal control is established.In order to alleviate the problem of urban traffic congestion and improve the traffic capacity and service level of road sections,a method of state consistent signal control with traffic flow uniformly distributed in the space of road sections is proposed.(3)signal control in supersaturated regionConsidering the maximum length of vehicles that can enter the road section at the upstream intersection in the remaining space of the road section,the maximum threshold for determining the queue length of vehicles is calculated.According to the traffic conditions of the upper and lower sections of the traffic network,a dynamic phase combination method is proposed to reduce vehicle delays and parking times,which can effectively reduce the possibility of overflow at intersections.Establish a signal fuzzy control system.(4)boundary controlThe method of sub-zone boundary control is proposed.The research of boundary control takes delay and shortest total travel time as control objectives,establishes corresponding optimization models of traffic control subsystem and traffic guidance subsystem,and establishes a cooperative optimization objective function of comprehensive performance indexes through cooperative optimization.Finally,taking Kaifeng city as an example,the comprehensive application of sub-district dynamic division,traffic state consistent signal control,dynamic phase combination and variable phase sequence control methods is simulated and verified.