Town Road Network Optimization Design Based On Vulnerability

As the carrier of traffic activities, road network is constantly expanding and developing for the past few years. At the same time, it’s risk under disasters also increased, and the vulnerability to withstand disasters ability has constantly exposed. Vulnerability is an inherent property of the road network, which reflects how badly road network and road network units will be affected under various interference factors. Therefore, it is necessary to further study on the influence factors and influence degree of road network vulnerability and to identify key roads and key nodes. It is very important to reduce the risk of road network through the introduction of the vulnerability. Combined with the survey data, this paper discusses the road network vulnerability under debris flows disaster, and applies the results to the optimization design of the road network.This dissertation makes a comparison with the concept of road network vulnerability and reliability、risk, the influencing factors of road network vulnerability are also proposed and analyzed, namely network scale, network topology and evacuation behavior. Summarizing the behavior characteristics of residents to evacuate through statistical processing of survey data. Summing up the influencing factors based on the nested logit model. Evacuation behaviors have an impact on road network vulnerability, which can be described as the uncertainty of traffic flow distribution in time and space which influenced by evacuation behaviors.Constructing a demand vulnerability index based on the analysis of evacuation behaviors, and taking into account of the network topological structure and dynamic characteristics, selecting demand vulnerability index, betweenness index and effective index from the dynamic, static, as well as the dynamic and static three angles, obtained weighting of each index by subjective weighting method to build a comprehensive vulnerability assessment index.Through the introduction of the vulnerability constraints, the establishment of the double-layer model which express the capacity optimizing is given, whose upper layer aims at minimization of the Generalized travel cost, and the lower level is the combined travel demand model which considering evacuation behavior. A method combing genetic algorithm and simulation analysis is proposed to solve the proposed model.