Vulnerability Estimation And Control Strategy Of Public Transportation Systems

Public transportation system refers to the engineering facilities that provide public transportation services for material transportation and residents travel.China is a country with a large territory and a huge population,and public transportation system plays an important role in the economic development and people's daily life.Meanwhile,since the meteorological and topographical conditions of China are complicated and natural disasters happen frequently,transportation systems are suffered many kinds of hazards and attacks.So studying the vulnerability of the public transportation systems under kinds of disasters and the corresponding vulnerability control strategy is an important subject related to thenational welfare and people's livelihood.In this thesis,we study the vulnerability analysis method and corresponding vulnerability control strategies for public transportation systems under different kinds of disasters.The research results are applied to Chinese railway system,Chinese airline system as well as the bus system and subway system of Wuhan city under several kinds of disasters.In this thesis,the system vulnerability is defined as the performance decrease of the system under disaster.Based on this definition,the thesis proposes a general framework to analyze the vulnerability of public transportation systems,which mainly includes the following four steps: First,the network model is adopted to describe the public transportation system;Secondly,the hazard models(flood,earthquake,etc.)are built to generate the disaster scenarios,and the vulnerability function of system components under different hazards are used to estimate the damage state of system components;Thirdly,based on the performance metrics of the public transportation system and the damage states of system components under disasters,the vulnerability(the decrease of the system performance)of the public transportation system is obtained;Finally,the public transportation system maintenance strategies are designed and the effect of these maintenance strategy are estimated.Flood and earthquake are two kinds of most common natural disasters in China,which have caused a great loss to the public transportation systems.For example,in 1991,the flood of the Huai river made the railway service in the province of Wan,Gan,etc.shut down for more than 3200 hours.In 2008,18 railway lines,with 6587 km operating distance in total,are affected by the Wen Chuan Earthquake.Therefore,this thesis collected the historical data of the two types of natural disasters(to set up corresponding disaster models).The proposed vulnerability analysis framework is used to study the vulnerability of the Chinese railway system under these two types of disasters(floods and earthquakes)and the corresponding vulnerability control strategies are presented.Different public transportation systems are not independent.There are mainly two kinds of relationships between different types of transportation systems: competition and complementary.For example,passengers can choose railway or airline for their long distance travel.In normal days,these systems compete for passengers by price or some other convenient characteristics,but in peak days like the Spring Festival,they complement each other to transport passengers to their destination.When considering vulnerability,the complementary relationship is more important than the competition relationship,because complementary can reduce the system vulnerability by providing alternative transportation service.As an extension of the vulnerability analysis of the single public transportation system,the thesis further discusses how the complementary relationship impacts the vulnerability of the systems.Taking two levels of complementary public transportation systems(railway system and airline system at the national level;bus system and subway system at the city level)as examples,the thesis analyzes the vulnerability of the complementary public transportation systems.When study the vulnerability of the national level compelementary transportation system,the SLFs(Spatially Locally Failures)is used as disaster model.Both flood and earthquake can be regarded as a specialization kind of SLFs,as well as the bombs events and extreme climate,which can cause components in an area fail.Thus,the vulnerability analysis of the public transportation system under SLFs is an extension of vulnerability analysis under natural disasters mentioned above.In the thesis,the public transportation system under flood disaster,earthquake disaster and SLFs are used as examples to show the application of the proposed vulnerability analysis framework.The framework can also be used to analyze the vulnerability of public transportation system under other types of disasters,such as hurricane,debris flows,rainstorm,only if the disaster model and the component fragility function is available.In this thesis,the discussion of the vulnerability analysis and the vulnerability control strategies of the public transportation system could provide decision support for the goverment or related stakeholders when they make decision about the maintenance plan for the public transportation systems,and improve the reasonability and effectiveness of the decision making process.