The Methodology For Recognition Of Oversaturated Intersection Based On The Cell Transmission Model

Now some intersections of urban road networks are often in the state of oversaturated conditions. Oversaturation causes the urban road network traffic failure, seriously hinders the efficiency of urban activities. So understanding the mechanism of oversaturation, recognition and evaluation of oversaturation are key points to prevention and governance oversaturated traffic.First, the oversaturated traffic was analyzed in aspect of predisposing factors, formation mechanism and discussed the characteristics in instability, space diffusivity, time continuity and failure of green time. According to these characteristics of oversaturated traffic and considering the basic theory of traffic flow, the simulation model was established to face with the features of oversaturated network based on the Cell Transmission Model (short for CTM).Then, based on analyzing the macroscopic traffic index and features of oversaturated traffic, the recognition and evaluation alternative indicators of oversaturated intersections were determined. By setting the different coefficient of traffic demand, the simulation model simulated how the alternative indicators changed along with the simulation time under different coefficient. Alternative indicators were extracted and the change trend and change range of the indicators were compared. Then the applicability of the indicators considering road network structure was summarized and ultimately the queue strength was determined as the key indicators of oversaturated recognition.Last, according to the key indicator queue strength of oversaturated recognition, two methods based on the minimum queue strength and maximum queue strength were put forward to identify oversaturated intersection, and two threshold values of identification methods were determined. In terms of oversaturated evaluation, based on the correlation between indicators, alternative indicators were classified and fitting function between indicators were worked out. Then the variable evaluation indicator method and comprehensive index of oversaturation state were proposed to evaluate oversaturated intersections. Finally, the example to value the oversaturated intersection was carried out.