Research On MFD Characteristics And Boundary Control Method Of Road Network Based On Regional Variable Speed Limit

In order to alleviate the regional traffic congestion problem,the paper relies on the National Natural Science Foundation Project "Intelligent networking environment traffic congestion area spatiotemporal evolution mechanism and dynamic boundary control method(No.52072108)" and National Natural Science Youth Foundation Project "Congestion network eigenextraction and rapid evacuation algorithm based on spatiotemporal detection(No.61304195)".Based on Macroscopic Fundamental Diagram(MFD),a perimeter control method combining variable speed limit control and optimal control is proposed.The main contents of the paper include the following aspects.(1)Through simulation analysis,this paper studies the influence of different speed limit conditions on road network MFD.The results proves that the higher the speed limit value is,the higher the travel completion rate of road network is;The more speed limited sections,the greater the impact on the travel completion rate of the road network;The speed limit of boundary section has a greater impact on the travel completion rate of road network than that of central section.(2)In view of the difficulty in obtaining the traffic density of road network in traditional sub-zone division,combined with the relationship between traffic density and speed,the idea and theory of node contraction method is adopted.Finally,a sub-zone division method is proposed,which based on the ratio of average speed of road section to speed limit value of road section.(3)Based on the vehicle dynamic balance model and the cellular transmission model,the variable speed limit control model of congested road network is established.The variable speed limit control is applied to the boundary of congested sub-zone to reduce the cumulative number of vehicles in congested zone.Then,the optimal control is used to adjust the input and output of each sub-zone,so that the vehicle travel completion rate of each sub-zone is optimal.(4)Taking a local road network in Hefei as an example,the paper compares and analyzes the Variable Speed Limit and Optimal Control method(Short for VSL-OC),the Optimal Control method(Short for OC)and the Proportional Integral control method(Short for PI).In addition,the traffic operation parameters such as the cumulative number of vehicles,the travel completion rate,the traffic delay and the traffic energy consumption under the three control methods are compared and analyzed.The results show that the proposed VSL-OC method can not only alleviate the traffic congestion,but also effectively improve the operation efficiency of each sub-zone of the road network。Compared with no control,the average vehicle delay of the whole road network is reduced by about 21%,and the average vehicle energy consumption of the whole road network is also reduced by about 48%.