Integrated Resilience Assessment Of Urban Transportation Network

Urban transportation network is an indispensable part of a city.It can provide basic transportation services for the city,and is the basis and key to ensure the normal operation of other functional systems of the city.However,the urban traffic network will inevitably be disturbed by various abnormal events,which will not only damage the physical facilities of the traffic system,but also affect the normal operation of social economy,resulting in serious economic property losses.Therefore,it is quite significant to study the urban transportation resilience feature after disturbances,analyze factors associated with resilience and figure out the resilience ability of different cities.This paper takes 40 major cities in China as research samples and studies resilience from perspectives of network topology and transportation function.Firstly,build an integrated resilience assessment model using publicly accessible datasets.This integrated model contains three parts:(1)traffic flow simulation,(2)adverse events simulation and(3)impact analysis.With respect to traffic flow simulation,the study area is split using Voronoi region.Travel demand in each region is calculated based on population data.Traffic flow in each road segment is obtained through traffic flow assignment.We apply publicly available congestion index datasets to calibrate and validate the model parameters.20 cities datasets are used to calibrate model parameters,and model -(60)is 0.825.Other 20 cities datasets are used to validate model parameters and -(60)is 0.632.All these validate the model.With respect to adverse events simulation,real-world adverse events are abstracted as random,localized and flood disturbance.Ca Ma-Flood model is used to conduct flood simulation to get inundation depth of each road segment.The model outputs,after damage types and damage intensity are determined,congestion index and fractions of giant connected component are used to analyze topological and functional resilience.Then,resilience values under different damage intensities of each city are obtained after applying the developed model and conducting 10080 independent simulations.Relative resilience is introduced to study each city’s resilience better.This study finds that functional resilience improves even if more links are disrupted within a certain damage interval.We quantitatively find out reasons for this typical resilience feature by studying the distribution of congested flow throughout the network.That is with more links disrupted,less OD demand can get into the connected components.Meanwhile,disruptiveness of each damage types is quantitatively analyzed.In most cases,flood is the least disrupted one,random damage is the most disrupted one and localized damage lies between them.In addition,this paper introduces generalized resilience by calculating the area under the curve of initial resilience--damage intensity.Correlation and regression analyses are conducted to find out potential impact factors of resilience and their influence mechanism.Regression model containing factors of total road length,population,and starting congestion index can reasonably estimate functional resilience under all three types of damages with -(60)larger than 0.6.Topological resilience under random and localized damage can be estimated by the combination of betweenness centrality and average degree with -(60)near 0.5.Finally,we introduce resilience ability by calculating the area under the curve of relative resilience--damage intensity.We find some cities with some typical resilience features.For example,Shanghai’ road network is resilient under all three damage types measured by structural resilience,but it is not resilient under the measure of functional resilience.This paper analyzes reasons for the typical resilience features using the regression result.Categorize these cities into three groups and propose effective predisaster preparation measures and mitigation strategies.