Study On Urban Road Network Carrying Capacity Based On Self O7rganized Criticality

With the rapid development of national economy and the increase of the motor vehicle ownership, traffic congestion is getting more serious. When the road network traffic reaches a certain level, it will show self-organized criticality, at this time, tiny disturbance may lead to local or large area congestion accidents, and it will cause serious economic, social influence directly or indirectly. Preventing the road network traffic flow from reaching self-organized state, or when the system reaches the self-organized state, destroying the self-organized state of the system can prevent a large area of traffic accidents in a certain extent. This paper discusses the SOC of the road network traffic flow by using sandpile model. Combined with the actual road network in Beijing, this paper made qualitative and quantitative researches on road network carrying capacity from the perspective of SOC.Firstly, according to the data of road running status and traffic congestion index in separated time periods of city road network between2008and2012in Beijing, it can determine the road network traffic has SOC. Based on the SOC characteristic of road network traffic, this paper define the urban road network carrying capacity, and give the corresponding mathematical representation.Secondly, combined with road network attributes, the tendency of the driver to change the path and applicable conditions of SOC, the paper establish the road network sandpile model, simulating the evolution of the road network traffic. In addition, the paper draw the road network topology by CA model, write the evolution of the road network sandpile model by using JAVA software and establish a quantitative model of road network carrying capacity with the results of the network sandpile model by MATLAB.Finally, the paper validate SOC of the actual road network, and obtain the corresponding network carrying capacity of the road network by simulating. Theoretically, by changing constraint conditions of the model, we know the increase in traffic volume does not change the characteristics of the road network traffic, congestion scale sequence and the value of road network carrying capacity; however, changing a single road traffic constraint elements, that is a given maximum load ratio, it will destroy the SOC characteristics of the road network, preventing the occurrence of a large area of congestion accident to some extent.