Fuzzy User Equilibrium Traiffc Assignment Model Based On Credibility Measure

Traffic assignment is the important step of four-stage forecast in transportation planningand the theoretical foundation of transportation network design. Affected by the complexity ofthe traffic network and uncertainty of the traffic situation, the behavior of users is alsouncertain in their travel choice. Taking full consideration of the uncertainty, the userequilibrium traffic assignment is studied based on fuzzy credibility theory in this thesis, whichhas important theoretical significance for transportation planning under uncertainty.Firstly the uncertainty of the travel choices analyzed in detail and the existed methods tomeasure various uncertainties are compared. Considering that the level of traffic informationhas been continuous improved nowadays and the traveler can get mass auxiliary information,the author think the perception of traveler is not purely random and has certain determinacy,but it is fuzzy. Meanwhile, the analysis of the possibility of travel choice of traveler hasn’tconsidered the necessity of behavior, when it is applied to practical application, it has greatdeviation. Taking full consideration of the advantages of credibility in dealing with possibilityand necessity simultaneously, the author use it to measure uncertainty of travel behavior. Then,using triangular fuzzy number to measure road impedance and taking credibility as utilityvalue to routing, the author established the shortest path model and fuzzy user equilibriumtraffic assignment model based on credibility. Referring to the fuzzy expectation of theshortest path, the concept of fuzzy efficient path is defined and an algorithm is designed. Onthis basis, a MSA algorithm is applied to solve the fuzzy user equilibrium model. Using onesimple road network, a simulation test is made based on randomness, possibility andcredibility. The result shows the methods present in this thesis are efficient and available.The purpose of this thesis is to provide new ideas and methods for uncertainty. The resultof this study not only can directly provide traveler behavior analysis to support the theory ofuncertain traffic assignment, but also apply to transit traffic assignment, traffic risk analysisand other area.