The Methods Of Resilience Evaluation And Promotion For Multi-Modal Public Transit Networks

Due to the expansion of urban scale and regional economic circle,residents’ transportation is developing towards the direction of long-distance and combination of multiple transportation modes.Single mode transportation has been difficult to meet people’s complex travel needs,and the multi-mode public transit system with conventional public transport and rail transit as the main body has gradually become the focus of meeting people’s daily travel needs,restraining car travel and alleviating traffic congestion.As an important part of urban residents’ transportation,public transit systems may face risks and challenges from natural disasters,social security,equipment failure,man-made destruction,pneumonia outbreak and other emergencies.Once the system fails or collapses,the economic losses,casualties and social impact will be immeasurable.Therefore,it is more necessary to pay attention to the improvement and shaping of the concept of resilience.This paper takes the multi-mode public transit networks as the research object,and proposes a multi criteria resilience evaluation method.In view of the interruption of some sections of metro,the design method of emergency connection between metro and bus based on resilience improvement and the optimization method of multi-mode public transit networks restoration sequence are proposed,and the core area of Nanjing is selected for case analysis.The main work of this paper includes the following aspects:(1)A multi-mode public transit networks topology model based on super network.Based on the super network theory,this paper introduces the constituent elements and construction methods of multi-mode public transit networks.Firstly,the road,bus and metro network topology model and computer expression composed of node and arc are constructed hierarchically.Then,based on the super network model,the network expansion technology is used to add virtual nodes and virtual arcs to build a multi-layer composite multi-mode public transport network topology model,and the multi-mode public transit networks information expression method with convenient reading and reasonable storage is designed.It provides basic data support for subsequent network resilience evaluation and optimization.Finally,the core area of Nanjing is taken as an example to show the operability of the model method.(2)Multi criteria resilience evaluation method for multimodal public transit networks.Based on the existing research,this paper summarizes the definition and connotation of resilience,puts forward the strategy of improving traffic resilience,and constructs a resilience index model to quantify the resilience change trend of the network.According to the characteristics of multi-mode public transit networks,starting from the two aspects of network topology characteristics and network supply and demand characteristics,with the help of analytic hierarchy process,a resilience index is constructed.The system includes local and global indicators to comprehensively describe the network performance.Trans CAD is used to simulate multiple failures of the network to obtain a variety of sample data.Standardized processing is carried out according to the degree of data deviation from the normal value.The improved entropy weight method is used to calculate the index weight and comprehensively evaluate the network resilience.The evaluation method can obtain the resilience index of a single index and the comprehensive resilience index of the whole network.The evaluation method is more flexible and the results are richer.Finally,taking nanjing road network as an example,the effectiveness and operability of the method are verified.(3)Design method of bridging bus emergency between metro and bus based on resilience improvement.In the case that some sections of metro are shut down due to failure,a bridging bus emergency model and algorithm between metro and bus based on resilience improvement are designed.Firstly,the damage state of metro network is analyzed,and the threshold and service range of emergency bus are obtained.Secondly,combined with the analysis of the impact of metro operation interruption on the network structure and passenger flow,based on the available network structure and bridging bus,the OD demand of metro is estimated,and bridging bus line generation model with minimum passenger delay is constructed.Based on the completion of the emergency connection network,the Logit route selection model is selected to calculate the passenger flow demand for bridging bus.Then,an emergency bus configuration model is proposed to maximize the resilience index of the evacuated passenger flow,so as to improve the passenger flow evacuation efficiency and reduce the empty running of the bus.Finally,Nanjing Metro Line 3 is taken as an example to verify the effectiveness of the model and the efficiency of the algorithm.The results show that passenger delay mainly comes from waiting time.The earlier the bridging bus is started,the more affected passengers will be attracted to choose the bridging bus.The passenger flow imbalance of the bridging bus section is relatively significant,and it is necessary to reduce vehicle idling through circular scheduling and multi-point evacuation.(4)Multi-mode public transit networks restoration sequence optimization method based on resilience.After some sections of metro were shut down due to faults,a multi-mode public transport network restoration sequence optimization method considering system coupling characteristics is proposed.Based on the weight of multi-mode public transit networks resilience evaluation index and considering network cascading failure comprehensively,a multi-objective network restoration sequence optimization method under repair resource constraints is constructed,and NSGA-II algorithm is designed to solve it.The optimization goal is to maximize the average efficiency of the network on the premise that the modified maximum link graph and network blocking coefficient meet the resilience requirements.The optimization model can not only reflect the final result of network repair,but also reflect the impact of the repair process on the optimal scheme.Finally,taking Nanjing Metro Line 3 as an example,the effectiveness of the repair model and the efficiency of the algorithm are verified.The results of sensitivity analysis show that increasing the number of synchronous maintenance teams can significantly improve the network resilience,while over investment has little effect on the network resilience.The uncertainty of repair time has a great impact on the results.