Research On Accessibility Modelling Measurement And Improvement Strategy Of Public Transport Network

With the acceleration of China’s urbanization process and the advancement of industrialization level,urban traffic problems have become more and more serious.Problems such as traffic congestion and environmental pollution have negatively affected the urban appearance and the living standards of residents.China is a country with a large population,high residential density,and a lack of land resources.Public transport has the comparative advantages of large capacity,high efficiency,low energy consumption and low pollution.Therefore,the development of public transport can effectively solve the traffic problems faced by China.Accessibility is an important index to evaluate the rationality of the transportation system.This paper evaluates the urban transit system from the point of accessibility,and put forward the improvement strategy.This paper firstly analyzes and summarizes research about accessibility by domestic and foreign scholars,systematically analyzes the four types of influencing factors and applications of accessibility,introduces traditional accessibility evaluation models,and analyzes the advantages and disadvantages of each model.According to the research purpose of this article,transit accessibility is defined as the degree of difficulty for urban residents to reach their destination under certain conditions of urban land use by public transport.The generation of transit network is the basis for accessibility measurement.This paper designs a fast method to generate a super network by expanding virtual nodes and virtual links according to the practical bus network.The super network is divided into driving links,transfer links,boarding links and alighting links according to the complete public transport travel chain.The definition and search algorithm of effective route are provided considering the actual travel characteristics of passengers.Impedance is an important factor in accessibility modeling.The links in the super network are weighted according to three factors,which are travel time,monetary cost and congestion,to construct the generalized cost function.Different form the traditional spatial barrier model only considering the travel impedance under the shortest path,this paper gets the average travel impedance by stochastic equilibrium assignment model,which can take the congestion and multipath factors.The accessibility concepts is divided into OD pair accessibility,regional accessibility and mobility and network accessibility.The rationality of the accessibility model is proved by an example.The paper finally puts forward strategies to improve the accessibility of public transport network.Regarding rail transit as a fixed line,adding and determining the terminal station,this paper constructs a candidate set of bus lines.For the target of optimizing the network accessibility and reducing the bus operating cost,a combinatorial optimization model and the solving genetic algorithms is designed.By comparing the spatial distribution of OD accessibility and regional accessibility,it is found that,after improvement,the accessibility of the network increased by 1.6%,the regional accessibility increases by 5.15% maximally,the regional mobility increases by 7.09%maximally.The results show that the transport resources will tilt to areas with large OD volume,which will aggravate the imbalance of spatial distribution of regional accessibility.