Dynamic Control Method Of Regional Traffic Volume Based On Macroscopic Fundamental Diagram

In order to solve the problem of low-efficiency traffic operation in the central area of city where congestion often occurs,based on the MFD(Macroscopic Fundamental Diagram)model,this thesis studies the total control of regional road network with the idea of combining internal traffic optimization and external total dynamic control.By utilizing VISSIM simulation,this thesis constructed a road network model based on the city center area on working day,through simulation analysis,the results show that there is a clear road network MFD,and there is a point at which the network is at the best level of operation(ie,the threshold point).On the basis of the initial scheme,seeking for better road network thresholds,this thesis studied the changes of road network MFD after major road network influence factors are improved.Through the simulation of intersection canalization improvement and signal timing optimization,the comparison of road network traffic conditions before and after the scheme shows that the improvement of these two factors can obviously optimize the performance of road network MFD.The two factors above are all based on the internal road network,so the road network plan which improves the two factors simultaneously is called the internal optimization project.After obtaining the MFD of the internal optimization project,the threshold point determined by the MFD is the basis for the network traffic volume control.Based on the feedback gate control principle,the network traffic volume dynamic control is realized relying on the self sensing signal lamp which is set at the upper intersection of the road network boundary.The purpose of the boundary upstream self-sensing control is to control the number of vehicles entering the road network from the upstream intersection,make it equal to the number of vehicles that let the road network operate at the optimal level,determine the flow into and out of the intersection using the threshold point of the MFD,then determine the flow of traffic into and out the upstream intersection and determine the timing of the self-sensing signal at the upstream intersection.Through simulation,this thesis realizes the dynamic control of total amount of road network with the help of self-sensing control of the boundary upstream intersection,so that the traffic volume and weighted average traffic of the road network are maintained near the expected threshold point.The assessment indicators of the road network show that after the implementation of the total dynamic control,the overall road network capacity and the service level of the traffic have been significantly improved.