Vulnerability Analysis Of Urban Rail Transit Network And Coordinated Access Restrictions Of Passengers

The urban rail transit system has become a major component of urban public transport in recent years due to its safeness, speediness and environmental friendliness. With the expansion of infrastructure networks and increase in passenger demand, the urban rail transit system also experiences disturbances from emergencies due to natural disasters, facility failures or terrorist attacks. These disturbances not only damage the infrastructure network and reduce the network connectivity, but also deteriorate the ability of transportation network seriously, which causes inconvenience to passengers. Thus, it is important to conduct vulnerability analysis of the urban rail transit system and optimize the emergency planning and operations.This research focuses on the urban rail transit system and applies the complex network theory and the transit assignment theory in it. There are three major parts in this research including the vulnerability of both the infrastructure network and the service network, reconstruction sequence of the infrastructure network and access restrictions of passengers after emergencies. The results of this research can serve as a decision support and a quantitative basis for both infrastructure network reconstruction and access restrictions of passengers. The content is as follows:(1) Vulnerability analysis of the urban rail transit infrastructure network:The vulnerability of the infrastructure network is analyzed from the aspect of topology structure. The effectiveness of the proposed approach has been demonstrated with a case study of Beijing subway through random and intentional attack experiments. The results indicate the most critical stations in the network.(2) Vulnerability analysis of the urban rail transit service network:This chapter develops a quantitative framework for assessing vulnerability of the urban rail transit service network considering passenger crowding caused by interruptions. The framework utilizes dynamic transit assignment to describe the time-dependent distribution of passengers in the system and uses generalized travel cost growth as the indicator of vulnerability of the urban rail transit service network. Simulation experiments are performed to examine the effectiveness of this approach using data from Beijing subway. The results of simulation test indicate the vulnerability of each section in the network and provide suggestions on the stations to implement access restriction control.(3) Rebuild sequence optimization of damaged urban rail transit networks:This research proposes a model to identify the optimal rebuild sequence of damaged urban rail transit networks that minimize the system cost. Day-to-day traffic assignment is integrated in this model to simulate the flow evolution during multi-stage rebuild process and Tabu search algorithm is utilized to solve the model. The method is implemented on a test transportation network. The results show that the generated rebuild sequence not only decreases the generalized travel cost and passenger congestion in the system, but also mitigates the passenger flow fluctuation in the network.(4) Coordinated access restrictions of passengers at stations:In order to mitigate the passenger congestion in the urban rail transit systems after emergencies, this research formulates the coordinated access restriction strategy of urban rail transit as a bilevel optimization problem and computes the appropriate passenger access amount in stations from the network level. Using the generalized travel cost as the indicator of service quality, the upper level objective is minimizing the generalized travel costs from the perspective of operators. The lower level model uses dynamic transit assignment to depict passengers’time-dependent route choice behavior. The simulation experiments are performed on Beijing subway to examine the effectiveness of this approach. Using a sensitivity analysis-based method, a heuristic solution algorithm is presented to solve this nonconvex problem. The proposed access restriction strategy can dynamically assemble urban rail transit stations to work together and effective coordinate the isolated restriction rates to leverage their strength for minimizing crowding in urban rail transit network.