Accessibility Analysis Of Large-scale And Multi-mode Public Transit Network Under Travel Time Uncertainty

Accessibility is an important indicator of traffic assessment.Therefore,the study of transit accessibility is of great significance and value in evaluating and improving existing transit services,providing decision support for transportation planning and individual itinerary.Public transit influences accessibility in unique ways,which operates on fixed routes,stops and pre-determined schedules,and travel time has the essential characteristics of time dependence and uncertainty.However,current research on the accessibility of public transport has received relatively less attention compared to car-based accessibility.In order to simplify the problem,travel time computation relies on over-simplified assumption that buses travel at the average speed,individual wait buses for fixed time and so on,which will undoubtedly affect the real accessibility.For the particularity and complexity of public transit,this paper aims to establish a flexible and efficient analysis method to solve the problem of public transport accessibility analysis under travel time uncertainty including data processing,spatio-temporal network model establishment,transfer algorithm design and implementation,accessibility analysis and visualization.The main innovations are as follows:Firstly,considering bus,subway and walking,a reliable time-dependent multi-mode spatio-temporal public transit network model is established on the basis of historical GPS data processing,which can realize the comprehensive analysis of accessibility at different time and space granularity.Secondly,an efficient route planning algorithm is proposed for large-scale and multi-mode transit network under travel time uncertainty according to the particularity of public transit,which is different from the traditional bus transfer algorithm,combined with the reliable shortest path algorithm based on road network.Based on the above method and innovations,a case study using real-world traffic information of Shenzhen is carried out to demonstrate the applicability of the proposed method.Accessibility is analyzed from the two perspective of reach area and accessibility to point of interest through public transit,and results reflect the impact of travel time uncertainty and time-varying on accessibility,which show that the proposed method is effective and the efficiency of the proposed algorithm is valid.