Evacuation Strategy Of Traffic For Urban Road Network Emergency

With the development of economic construction in our country,the income level of urban and rural residents was increasing steadily,the city car ownership also has increased greatly,the supply and demand contradiction of urban road traffic standing out,urban traffic congestion become a norm.The urban traffic main function was urban road network service level,once an emergency happened in urban road network,urban traffic paralyzed easily,it would influence the public transportation efficiency and the quality of life,this was a common problem.In recent years,unpredictable emergency such as road and bridges damaged or vehicle rear end collisions in urban road network,would weaken traffic capacity of urban road network,led to backup of network traffic,thus resulted in saturation of urban road network,the entire road network service level declined.Under emergency,the research methods of evacuation for road network traffic flow was classification of urban road network emergency incidents,judging the degree of urban traffic congestion after classifying event level,taking temporary traffic control for assignment evacuation according to traffic congestion degree,but with little success,one of the reasons was that there was no efficient traffic evacuation strategy under urban road network emergency.Therefore,it's necessary to explore evacuation strategy under emergency.This article analyzed service level classification of the urban road network,considering characteristics of the factors affecting urban road network under emergency,calculated evaluation index weight of influence factors using fuzzy analytic hierarchy process(FAHP),and established network service level hierarchical evaluation model under urban road network emergency.Secondly,considering relationship between traffic jam and adjacent nodes under network emergency in the city road network,according to the system equilibrium theory,taking minimum total impedance as objective function,established urban road network traffic distribution model under emergency,and analyzed model in optimal conditions by the Pontryagin minimum theory,designing methods for solving traffic diversion model,it was concluded that area network reasonable diversion scheme under urban road network emergency.Then,analyzed network topology of city road,according to the network variable structure theory,adjusted the fixed structure of road signs,logo line and the green wave traffic signal under city road emergency,forbidden limit to urban road intersection,using the strategy of assignment organizations such as forbiding turning left to reduce the network saturation,induced drivers to choose the shortest path,improved the road network traffic flow rate,reduced total delay caused by network event,ensured the safety of urban road network and smoothness of traffic flow.Finally,taking simulation software TransCAD for C city road network events somewhere unexpected as example,according to the study of assignment model and solving method of traffic evacuation strategy under road network emergency,carried on simulation and analysis,verified effectiveness of the model and the theory,practicability of the evacuation strategy implementation for network traffic.At the same time,saturation and service level of city road network could be timely feedback to the transportation department managers by simulation operation,this would improve the service level of city road network and enrich Intelligent Transportation System,providing effective traffic evacuation strategies under emergency.