Algorithm Of Variable Speed Limit Control For Contending With Highway Congestion

Highway is not only an important link between different cities,but also an important carrier of cross-regional traffic in cities.However,the growth rate of motor vehicles in China is obviously higher than the increasing pace of highway construction and traffic management level at present.That leads to the increasingly problem of highway traffic congestion.The variable speed limit control can fully reflect the dynamic characteristics of the highway system,and has achieved certain effect in controlling the congestion of highway.However,the present research still has shortcomings such as lack of precision,single control target and poor control effect.This thesis selects the highway congestion section for the study,This thesis proposes an algorithm of variable speed limit control for contengding with highway congestion.Based on the current model of METANET traffic flow,this thesis studies the critical density of highway congestion under variable speed limit control based on the principle of variable speed limit control.An improvement was made to the traffic volume of the starting section,the sensitivity of the speed and density,and the Ramp entry model.Then the model parameters are identified and validated by least square method.This thesis presents a more reasonable and accurate description of the change of traffic flow under variable speed limit control and increases the accuracy of traffic prediction.Based on the improved traffic flow model of METANET,the variable speed limit control system will seek the optimal speed limit by optimizing the control target.Based on the advantages of "high speed,high traffic volume and high service level" of highway,This thesis starts from the Angle of traffic benefit and environmental benefit,it selects the bottleneck area,total traffic volume,total travel time of the network and the emission of the vehicle exhaust emissions to control the target,and create a variable speed limit multi-target optimization model.In addition,the vehicle exhaust emission index is matched with the METANET traffic flow model,and the vehicle exhaust emission quantitative calculation based on the METANET traffic flow model parameters is realized.Then,the genetic algorithm is used to solve the model,and the fitness function is normalized by linear regression,then the judgment matrix is established,and the weight is calculated by the square root method.The multi-objective optimization problem is transformed into a single objective optimization problem.On this basis,the solution method of the model is provided.In the final article,South Ring Interchange to Jiqing Tunnel Section of G75 Lanhai highway is Selectsed in the Banan district of Chongqing to build a simulation.This article uses Python software to redevelop the VISSIM simulation software to implement the dynamic change of the speed limit in the process of simulation.The simulation results show that compared with the static speed limit control,the control algorithm based on the variable speed limit of highway congestion can improve the traffic efficiency,reduce the running time of vehicles and reduce vehicle exhaust emission.The research results of this thesis can provide reference for the development of speed limit control speed limit of highway congestion,which is of practical significance to improve traffic efficiency and environmental benefit of highway congestion.