Method For Traffic Control Of Urban Oversaturated Road Network Based On The MFD

Oversaturated traffic control is a difficult problem to relieve traffic congestion.In order to alleviate the oversaturated congestion of the road networks,this dissertation proposes a control method for the oversaturated traffic network based on the Macroscopic Fundamental Diagram of urban traffic.The following three aspects of work have been specifically carried out:First,a traffic optimization control model for road network based on the Macroscopic Fundamental Diagram is establish.A discrete state equation of road network traffic flow is established using the numbers of vehicles on the intersections and their adjacent sections as the state variables and the green light times of the intersections in the controlled road networks as the control variables.Then,based on the Macroscopic Fundamental Diagrams of the road networks,the optimal control objective,the vehicles accumulation number in the road network controlled within a specific range,is proposed;And then the oversaturated road network traffic control model based on the MFD is constructed by combining with the constraints of the conversions of numbers of vehicles entering and leaving the road links in a road network,and signal control constraints.Second,the algorithm to solve the optimal control model of road network traffic is designed.Aiming at the MFD-based oversaturated traffic control model for the road network,according to the Pontryagin's minimum principle,the equivalent nonlinear equations is established based on the KKT condition derived from the Hamilton function.The equations are solved by the ROSEN gradient projection method.Third,the MFD control strategy is verified on the real road network.For this purpose,taking the CBD road network in Dongjin District of Xiangyang as a case application,the results of MFD optimization control and Webster timing control results are compared in terms of the throughput flow rates,the cumulative numbers of vehicles entering and exiting the road network,and the abilities of traffic deadlock prevention.The case study shows that the MFD optimization control can prevent the oversaturated traffic congestion of the road network,and its control effect is better than the classic Webster timing control effect.The research shows that the road network traffic optimization control model and its solution algorithm proposed in this paper can improve the overall traffic capacity of the road network,effectively prevent and alleviate oversaturated traffic congestion,and provide a basis for regional macro-level traffic control strategies.