Study On Schedule-based Urban Rail Transit Dynamic Passenger Assignment Model

With the development of Chinese urban rail transit(URT),the network structure has become increasingly complex,and the passenger demand has continued to increase.What follows is the imbalance between traffic supply and demand and the complicated evolution rules of passenger flow.It often causes severe network congestion and even leads to passenger safety issues.Therefore,a reasonable and effective method of passenger assignment is urgently needed to study the current complex passenger travel behavior and the dynamic evolution rules of passenger flow in URT under crowded conditions,in order to accurately grasp the distribution of passenger flow.In addition,the theoretical model needs to be scientifically modeled on a technical method and effectively verified in practical application.Based on the existing research of dynamic passenger assignment in URT,the URT network structure is analyzed and a schedule-expanded network combined with train schedule that includes time-space dimensions is constructed to perform low-level modeling.And the shortest path algorithm under the schedule extended network established.Then,a generalized travel cost function is proposed to quantified the influence of main factors such as travel time,waiting time,number of transfers and congestion on passengers’ travel choice behavior.It reflects the passenger heterogeneity,and can truly reflect the route selection tendency of passengers in real travel process.To solve the problem of passenger route selection,the improved shortest path algorithm is proposed to solve passengers ’ expected shortest path.The algorithm consists of three stages:(1)The fastest path in the forward network;(2)The shortest path in the reverse network;(3)The branch and bound method of optimal path.The principle the algorithm is to determine the expected shortest path by the earliest arrival time(clock arrive time)and the latest departure time of passengers on the fastest path to the intermediate node.In this process,sub-net is constructed to speed up the computation.Finally,the dynamic passenger assignment model of URT is established by Monte-Carlo approach.Through the simulation method,the paper analysis the state of passengers in the network,studies the change rule of the passenger’s route selection behavior under different parameters,and justifies the choice of travel influencing factors and the accuracy of the allocation model.Based on the schedule-based rail transit passenger assignment model in the paper,it further takes the Shanghai URT as an example to conduct a case analysis.One day’s network passenger flow is used for passenger assignment,and the accuracy of the model is verified by comparing the actual travel time of passengers with the simulated travel time.Two strategies are provided to improve the operational efficiency and service quality,which are transport capacity allocation optimization and peak period flow limitation.