Optimization Of Correlation Parameters Of Entrance And Exit Combination Segment Of Expressway Continuous Interchange

Due to the develope of urbanization in China,the traffic demand is increasing,the city boundary is expanding,and the density of urban expressway net is increasing,and the distance between the continuous interchanges of expressways is getting closer and closer.Entrances and exits combination segment formed by continuous interchange.Combination segment is composited by merging segment,diverging segment and weaving segment.The condition of traffic flow is disordered and the traffic efficiency is limited in these segment.The correlation parameter setting of different combination segments of continuous interchange will directly affect the traffic efficiency of the entire expressway net and even the entire urban traffic system.The paper is supported by the content of National Natural Science Foundation of China " The Self-organization Mechanism and Correlation Design Parameter Optimization of Expressway Continuous Interchange Traffic Flow"(No.51878236)and Research Project of Hefei Priority Engineering Construction Administration "Evaluation and Research on Key Technologies of Traffic Design of Hefei Expressway System"(No.2019FFCJ4364).In this paper,the combination segment formed by two relatively close expressway interchange is taken as the research object.Genetic Algorithm was used to calibrate the driving behavior parameters of VISSIM simulation software.The speedchange lane length of directional ramp was calculated by means of theoretical analysis.And the calculation results were verified by the calibrated VISSIM software.Based on the recommended values of the speed-change lane length,the average speed of different combination segments under the influence of multiple factors was simulated and analyzed,and then the calculation model of the combination segment correlation parameters was constructed.Based on the calculation model,the application of the model was discussed.The result of the research shows that the relative error between simulation results and filed survey data is greatly reduced when the driving parameters of simulation platform were calibrated.So the calibrated simulation platform can meets the experiment requirements of the simulation scene.The results of study on the speed-change lane length of directional ramp shows that the recommended value of deceleration lane length of offramp on the leftt side of expressway mainlane is 135 m,and the recommended value of acceleration lane length of on-ramp on the leftt side of expressway mainlane is 215 m.The calculation model of the combination segment correlation parameters was constructed by analysised speed data of simulation.The results of discussion of the application of the model shows that controlling the the traffic flow of mainlane and onramp,reducing the weaving ratio and increasing the length of the combination segment can effectively improve the average speed of the combination segment.By analyzing the calculation results of the combination segment length under the conditions of the preset different speed value and influence factor value of combination segment,the recommended value of the combination segment length at different combination segment of the continuous interchange,namely the net distance between the continuous interchange,is determined,which plays a pivotal role in planning and design of the urban expressway network.