Research Of Coordinated Control Strategy On City Traffic Occasional Congestion

In recent years, with increasing of the urban population and vehicle quantities, urban traffic congestion has greatly affected the quality of residents’life, and it is a great waste to the road resources and economics. The urban road traffic congestion according to the causes of congestion can be divided to recurrent congestion and occasional congestion, recurrent congestion with regularity, and it can be predicted based on survey data and experience, and taking control measures at the same time. The occasional congestion is randomly occurring in time and space, and it also has a great derivative, its impact is often greater the than recurrent congestion.Currently, many scholars are working on the problems of occasional congestion, and having achieved some fruit. This paper relies on reading lots of literatures, analyzing and summarizing the results of their predecessors, and elaborating it by dividing into three aspects,which is testing and recogniting the scope of occasional congestion,the method of dividing congestion areas, evacuation strategies.And then,focus analysising the history of the research and development,achievements and the problems of to be solved.Congestion recognition is the precondition of evacuation for accidental congestion areas. The second chapter puts forward congestion fuzzy defined scope which based on the traffic wave theory, that is to say, judgment after accidental accident traffic wave propagation direction and velocity of covered area. Then within the scope of fuzzy definition, the traffic flow characteristic parameters as the indexes, identifying road traffic condition and determining the congestion area. Whether incidental congestion has been at the diffusion stage or disperse phase, the area of congestion are changing, therefore, in order to make the evacuation measures to achieve better results, at the same time avoid that the intersection under congestion control returned to normal results to the secondary accidents, this paper presents a dynamic plan which will define the congestion area. After the congestion areas identified, formulating corresponding measures to evacuation congestion area’s vehicle. However, when congestion range is larger, in order to simplify the control target for implementing more flexible in the area of the congestion control measures, and putting forward the division three control sub area methods in congestion and area around the congestion:blocking area,transition area and normal area. Three control area have their own characteristics and connect with each other at the same time.Traffic guidance and traffic control are two common means of achieving congested area evacuation strategy. In terms of traffic guidance, this paper in order to adjust the signal timing to build across the three main control area’s coordination control to optimize vehicle evacuation route, at the same time in normal area vehicle ban measures to implement the induced traffic measures.In terms of traffic control, realizing the self-organization scheme of signal timing in three control subareas which is based on real-time traffic parameters:In the blocking area,dredging vehicles from the intersection on the edge to the center of congestion; In order to balance the traffic pressure,according to the remaining capacity of the road to adjust the signal timing in the inner layer of transition area. And in order to transfer vehicles to normal area,according to prevailing demand to dsign the sheme of phases in the outside layer of transition area;Do the best to release vehicles on congestion exports through judging the key flow and regulating green light in normal area.Evacuation strategies in this paper as the normal area be unloading area and transfering the vehicles from blocking area to normal area to realizing the purpose of fast evacuation, which is based on the thought of Closuring peripheral area,unloading internal area".Finally simulating the methods of Traffic guidance and traffic control,and acoording the simulation results to analysising its effectiveness and feasibility.