Research On The Optimization Method Of Urban Traffic Signal Control Under Oversaturated State

With the accelerating process of urbanization and the increasing improvement of people’s living standards,the number of motor vehicles is also increasing greatly,and urban road traffic congestion is increasingly frequent and serious.Traffic congestion generally comes from local congested intersections or sections,and as time goes by,congested vehicles will gradually spread around to the whole road network.This paper takes the traffic regional road network as the research object,defines and calculates the regional traffic state analysis and traffic carrying capacity,and studies the optimization of regional signal control under the oversaturated state.The main research content includes the following aspects:(1)In order to accurately analyze the traffic state of regional road network,the traffic saturation under the unsaturated and oversaturated conditions was distinguished.The section weight coefficient was defined and the traffic congestion index,travel speed and other parameters were deduced and calculated from sub-sections to road sections to road network level to evaluate traffic operation conditions.The characteristic change relationship between traffic saturation and congestion index was studied.The generation and propagation mechanism of road network traffic congestion was analyzed,and the evaluation method of regional traffic state and operation was proposed.(2)The road traffic carrying capacity was defined and its general calculation formula was given.Then the influence of road channelization,in and out flow,signal control and other related factors on the carrying capacity was analyzed;in order to ensure the effective operation of the traffic at each entrance section of a single intersection under the oversaturated state,the calculation and optimization model of the traffic carrying capacity of a single intersection was determined and the maximum traffic carrying capacity of the corresponding intersection was obtained by combining with the calculation example by adjusting split,and the control effect is significant.(3)Aiming at the problem of traffic congestion in the urban area road network under the state of oversaturation,the corresponding static and dynamic congestion prevention and control strategies were proposed;then the corresponding traffic and signal timing were determined according to the correlation between the intersections in the road network,and the judgment criteria of traffic flow operation in the regional road network were given.Based on the judgment criteria,the dissipation of traffic congestion in the road network was analyzed and the traffic signal control optimization model and method were established to improve the traffic operation of the road network under oversaturated state.(4)The actual regional road network was selected as the research object to judge the operation of traffic flow,and the authenticity of traffic congestion was judged according to the traffic conditions of the road network at different times;for the false congestion,the congestion was dissipated to avoid the cumulative queuing of vehicles on the road section;for the true congestion,the signal optimization model was used to effectively improve the road network carrying capacity and delay as much as possible the time of queuing overflow on each section of the road network,so that it can carry more vehicles under normal traffic flow conditions.And the optimization effect of load balance in each section of the road network is obvious.