Vulnerability Analysis Of Complementary Public Transportation Systems

Public transportation systems play a crucial role in the economy development of a country or a city and the well-being of its citizen.In recent years,public transportation systems are subjected to natural hazards,sharply increase of demand,equipment failures and intentional attacks,which makes their failure probabilities increase yearly.Due to their importance,modeling and analyzing the vulnerability of public transportation systems have attracted growing attentions.Most previous studies mainly focus on the vulnerability analysis of single public transportation system and ignore the complementary relationships between these systems,which will affects the vulnerability analysis of public transportation systems.Railway system and airline system in a country or bus system and subway system in a city are typical complementary public transportation systems(CPTSs).This paper first proposes a vulnerability analysis framework for CPTSs,which mainly includes multi-layer networks model for CPTSs,system performance metrics selections,disruption modeling and vulnerability assessment,and the proposed vulnerability analysis framework is applied to investigate the complementary bus and subway systems in the city of Wuhan,China.In system modeling section,a three-layer networks model is used to model CPTSs,each system can be described by a network and inter-layer links represent the relationships between different systems;In system performance selection section,a network-based metric and a service-based metric are used to measure the performance of CPTSs and their assessment methods are also introduced;In disruption modeling section,three disruptions are considered,which includes random failures,degree-based attacks and betweenness-based attacks.Based on aforementioned vulnerability analysis framework,this paper introduces vulnerability analysis methods for CPTSs from three aspects:(a)vulnerability effects of passengers' intermodal transfer preference(PITDP),this paper uses dynamic complementary strength(DCS)to quantify the complementary relationship between different systems,and then analyses how PITDP affects the vulnerability and DCS of CPTSs,the results facilitate the design of polices to change PITDP to reduce system vulnerability;(b)vulnerability effects of subway expansion,this paper proposes a metric to quantify the dynamic vulnerability of transportation systems during system expansion process,called dynamic accumulating vulnerability(DAV),a greedy algorithm is proposed to find the optimal opening sequence by minimizing the DAV of bus system during the subway system expansion process,the results facilitate the identification of the optimal opening sequence from the system vulnerability perspective;(c)Multi-dimensional vulnerability analysis of CPTSs,the accessibilities to achieve five kinds of urban public services for residential community(RC)based on CPTSs are used as metrics to assess CPTSs' performance in a multi-dimensional way,these public services include urban commuting service(UCS),medical treatment service(MTS),commercial service(CS),education service(ES)and inter-city long distance travel service(LDTS).The results not only offer insights into decision making of selecting a residential community for citizens,but also help design better urban public transportation systems.