Research On Theory And Method Of Congested Traffic Flow Assignment And Road Network Capacity Calculation

Traffic congestion is an inevitable outcome of urban development.In the state of congestion,road travel time increases when the traffic flow decreases,which is contrary to the traditional impedance model describe the positively relationship between the travel time and traffic flow.Therefore,it is necessary to establish the congestion impedance function and study the congestion road network user equilibrium traffic assignment problem,this study could provide a theoretical reference for traffic simulation software development,congestion propagation mechanism study and traffic planning work.Urban road network capacity describe the ability of road network to deal with traffic demand,it is a key indicator to measure the operating status of traffic network.The bi-level programming model is a classical model for solving the problem of city road network capacity,the planning objectives is the maximum traffic demand take the road physical capacity constraints and user equilibrium traffic assignment problem into consideration.This paper introduce the congestion road network user equilibrium traffic assignment into the bi-level road network capacity programming model,which enrich the road network capacity research theory system and provides a new way for urban road traffic planning management and control.This paper summarizes and reviews the domestic and foreign research,and is organized as follows:Firstly,we analyzed traffic flow in congested state,and proposed congestion impedance function,and study the equilibrium traffic assignment problem of all-congested road network based on it.Secondly,the road non-congestion and road congestion impedance function are combined to construct an extended road impedance function,the concepts of demand flow and through flow are put on and their relationship could describe the road non-congestion or congestion state,based on the extended road impedance function,the user equilibrium traffic assignment model take traffic congestion pattern into consideration is studied.Then,construct a bi-level programming model of road network capacity for the upper level planning is a maximum traffic through flow model,the lower is planning the user equilibrium traffic assignment model take traffic congestion pattern into consideration.Finally,the proposed model is applied in a small road network and its theoretical value is calculated,other main results are as follows:?Explain why the existing models have the small capacity estimation problem;?The change trend of the network traffic demand flow and traffic through flow are consistent with the actual situation.