Research On Traffic Congestion Characters And Gating Conrol Of Urban Network Based MFD

Research on the characteristics of urban road network congestion is a critical base for determining proper traffic control strategies,while the Macroscopic Foundation Diagrams(MFD)is an inherent attribute of the urban road network,which represents the relationship between the vehicle numbers in network and the network’s operating performance and reflects the characteristics of traffic congestion in urban road network.Gating Control is an effective measure to ease the urban road traffic congestion and thus the focus of researches on Urban Network Traffic Management and Control nowadays.It is used to ensure the network flow in the protection area being unblocked with the implementation of access restriction to main intersections in the core area under control,thereby enhancing the performance of the entire traffic network.This paper looks at the drawbacks of gating control theory,and studies the characteristics of traffic congestion in urban road network based on MFD,combining the onsite and simulated data of traffic flow in Kunshan.Moreover,an advanced gating control strategy based on Model Prediction Control(MPC)is proposed,with case analysis and performance evaluation conducted using MATLAB.The research analyzes the characteristics of traffic congestion in urban road network based on the simulation model built in PARAMICS and its traffic flow output,together with onsite flow data acquired from Kunshan Urban Road Traffic Operating Management System.The analyzing process includes time and space distribution analysis of urban road network using MFD and time series diagram,and macroscopic basic MFD deviation analysis using probability and statistical methods.Additionally,main curve and spline curve methods are applied to fit the curve of macroscopic basic graph,and derives the analytic formula as the basis for the gating control application.The research proposes a MPC based gating control strategy and explores a dynamic way to determine the control area.The control area dynamic determination method uses the density difference between the area to be controlled and the gating control protected area to be the judgment value of the region state variable and the basis for dividing the control area,which should be no greater than the density difference threshold.The MPC based gating control strategy turns the road network congestion issue into pure mathematical issues,targets at the minimized total travelling time in network,derives the model with MPC theory and solves it using Genetic Algorithm.To evaluate the performance of proposed methods,this paper conducts a case analysis of MFC based gating control strategy using MATLAB.The analysis focuses on two aspects:control process and the control effect.The network demand is adjusted according to the proposed method and the result is compared to the performance of existing control strategies,which shows that the MPC based Gating Control strategy can effectively reduce the cumulative number of vehicles in the network and make the network congestion evenly distributed.