Research On Freeway Traffic Situation Deduction Algorithm Based On Variable Cell Transmission Model

Under the influence of different external factors,various traffic phenomena appear in the road traffic environment,which makes the development and evolution of the traffic situation more complex and increases the pressure of the traffic control department.Therefore,studying the process of freeway traffic situation deduction under different conditions is helpful to find out the contradictions of traffic problems and optimize traffic control strategies.According to the changes of traffic flow under different conditions,the algorithms of freeway traffic situation deduction under normal conditions and external intervention are designed respectively,used to derive the evolution process of freeway traffic situation.First,the paper introduces the concept of situation deduction into the field of transportation,with the freeway traffic situation deduction as the study object of the paper.The research status in traffic flow theory,traffic situation deduction,and cell transmission model is summarized,then the research content and technical route of the paper are presented.Secondly,based on traffic flow theory,the traffic flow characteristics under normal conditions are analyzed according to the actual data.Basic parameters of traffic flow are calibrated based on the preprocessed data.Then the impact of traffic incident and traffic control on traffic situation deduction is studied,which provides theoretical support for the design of freeway traffic situation deduction algorithm.Thirdly,according to multiple transformation of traffic situation,the Cell Transmission Model(CTM)is selected as the prototype basis of the algorithm,then the limitations of the CTM are analyzed.From the point of variable cell length and metastable state theory,the basic variable cell transmission model(VCTM＿LS)without external intervention was obtained;From the point of capacity and speed,the derivative variable cell transmission model(VCTM＿LS,C&V)for external intervention is obtained.The variable cell transmission model lay a foundation for the design of traffic situation deduction algorithms under different intervention conditions.According to the requirements of situation description and the characteristics of the variable cell transmission model,indicators such as travel delay,impact range of congestion and duration of congestion are selected to represent the situation change of freeway traffic.Finally,based on the basic variable cell transmission model,the freeway traffic situation deduction algorithm without external intervention is designed,and the whole process of traffic situation deduction is realized based on the actual data of Beijing-Tibet freeway.It shows that the deduction effect is good.and the density error is8.28%,which meets the accuracy requirements;Based on the derivative variable cell transmission model,freeway traffic situation deduction algorithm for traffic event intervention is designed,the process of traffic situation deduction under different intensity classification,different durations and different derivative incident is given,and the influence of different traffic incident on traffic situation indicators is analyzed;On the basis of traffic incident,the algorithm freeway traffic situation deduction under traffic control intervention is designed,the process of traffic situation deduction under different control strategy intervention is obtained,and the influence of different control strategies on traffic situation indicators is analyzed.