Formation Mechanism Of Traffic Bottleneck Congestion On Expressway And Evacuation Method Of Vehicle-road Coordination

As the main evacuation channel in the urban transportation system,the expressway plays an important role in carrying the main traffic flow and improving the traffic operation efficiency of the road network in the operation of the urban transportation system.The traffic operation of urban expressways presents the situation that the traffic of the whole line and even the whole road network is blocked due to a single bottleneck point.It is urgent to discuss the traffic operation rules of the bottleneck area and propose methods and strategies to alleviate congestion.Study the evolution law of the formation and dissipation of urban expressway traffic flow congestion,explore the formation mechanism of congestion from two dimensions of time and space,and propose a vehicleroad coordination allocation scheme for expressway congestion relief to improve the traffic efficiency of the urban road network.In addition,relying on traditional traffic management and control technologies and methods is not enough to effectively alleviate the contradiction between the current huge road traffic demand and limited service resources.With the continuous development of roadside global sensing,C-V2 X,edge control,and other technologies,the vehicle-road collaboration system can have more accurate and efficient sensing and computing capabilities to achieve dynamic control of lane-changing vehicles from a macro perspective.First of all,the configuration and basic characteristics of the traffic flow of urban expressways are comprehensively introduced.Based on the traditional basic graph theory and three-phase traffic flow theory,the basic parameters of the bottleneck section of the expressway are investigated and collected,and the traffic characteristics and operating conditions of the bottleneck section of the expressway are deeply explored from the two aspects of the change characteristics of traffic flow parameters and the operation characteristics of traffic flow,to provide a theoretical basis for the traffic flow control and road parameter optimization of the bottleneck section of the expressway.Secondly,select the expressway weaving area,which is the traffic flow frequency variation area,to study the traffic operation status,change process,and evolution law,and determine the traffic status criteria.The traffic simulation platform Vissim software is used for simulation analysis.The simulation results show that there is an obvious mutation phenomenon when the traffic flow transforms between free flow and congested flow.Applying spectral clustering analysis algorithm to accurately extract the boundary of traffic state mutation,combined with cusp catastrophe theory,research and analyze the traffic flow state at different times and different locations,which can fully display the evolution characteristics of the traffic flow state.The research results provide a theoretical basis for formulating traffic flow control measures and traffic congestion dissipation strategies for the expressway.Then,the cell transmission model(CTM)is used to explore the formation mechanism of complex traffic flow congestion in the bottleneck section of the expressway.Due to the limitations of the traditional CTM model,the basic CTM model is improved by considering the variable cell length and the three-phase traffic flow theory.The simulation results show that the error of the improved VCTM＿LT model is about 2.36%,which meets the requirements of the urban expressway traffic flow propagation law.Based on the characteristics of the VCTM＿LT model and the need to describe the formation mechanism of congestion,traffic delay,congestion queue length,and congestion duration are selected to characterize the mechanical characteristics of the formation process of traffic congestion on the expressway.Based on the actual traffic flow data of Jinshui Expressway,the research on the formation mechanism of traffic bottleneck congestion on the expressway is realized.Finally,the paper analyzes the characteristics of vehicle road cooperation operation in the bottleneck section of the expressway,establishes the dynamic assignment model of traffic flow in the bottleneck section,uses C-V2 X,edge computing,and other technologies,designs the dynamic assignment system of vehicle flow based on vehicle road cooperation,and studies its operation mechanism.The improved VCTM＿LT model is used to simulate and analyze the vehicle flow distribution system.The simulation results show that the optimization effect of the dynamic distribution system is obvious.The traffic time can be reduced by about 11.4% in the synchronous flow state,and the traffic time can be reduced by 39.7% in the congestion flow state.The research results are of great significance to reduce the operation delay in the weaving bottleneck area of the expressway and improve the operation efficiency of the traffic flow and the capacity of the expressway.