The Identification Method And Application Research Of Urban Road Network’s Vulnerability Under Emergency

With the advancement of China’s urbanization construction process,the urban road transportation network is expanding and deepening the transportation function.At the same time,some emergencies(such as natural disasters,traffic accidents,road maintenance,festival parades or terrorist activities)will emerge,which has a huge negative impact on the normal operation of the road network.Under this background,relying on traffic information from multi-sources,it is of great practical value and practical significance to focus on the development of integrated decision-making simulation platform for early warning,risk assessment and emergency rescue under emergent environment.The essence of the above study is to analyze the vulnerability changes of the road network under sudden environment and establish some traffic flow distribution methods that consider the network vulnerability.However,in the current research on road network vulnerabilit y identification,the impact of emergencies on the random and time-varying characteristics of road network traffic flow has not been considered,and there is no general efficient identification method and appropriate simulation application technology to describe and expand it realistically.Therefore,from the perspective of road network vulnerability,this paper takes the system of emergency,road network and traffic flow distribution as the research object,and research on network vulnerability identification,vulnerability dynamic dynamic analysis,emergency rescue path selection behavior modeling and integrated simulation application platform design.Specifically,the research steps in this paper are mainly from the following aspects:Accidents are identified according to their types and levels,and the levels of the accidents are matched with the consequence of the accident s,so that it can be easily classified in the urban road network.The static vulnerability identification under the failure scenario of single network unit is taken as our research starting point.The random and time-varying characteristics of the road network system are not considered temporarily.The single network structure change and robustness analysis under the burst environment are used to construct a static vulnerability identification model under the complete failure of the road link or intersection,and the Lagrange multiplier method is used to solve the model efficiently,which provides a basis for subsequent research.Since different types of emergencies have different degrees of impact on the road network,this reaction is an increase in the number of failed network elements or an increase in damage on the network.Therefore,on the basis of the failure of a single network unit,the cascading failure simulation under the multi-links failure and the cascading failure simulation under multi-intersection failure are studied.Then,the differences between the complete failure and partial failure of multiple network elements are compared and analyzed,and the relationship between the robustness and vulnerability of multiple network elements is discussed.Considering that when an emergency event acts on a road network,the traffic capacity change of the link will be random,and the negative diffusion effect of the emergency event will significantly affect the path selection behavior of different types of travellers.Therefore,starting from the change of the links’ traffic by random factors,a balanced distribution model considering the path selection behavior of different types of travelers is constructed,and a new index is used to quantify the random characteristics of the road network vulnerability under the sudden environment.The efficient solution of the model is realized by road network compression and two-layer algorithm design.After that,the effects of the Logit model and the Probit model on network vulnerability analysis results are analyzed,and the existing models are improved.The research is further extended to the general scenarioes,in view of the "generation-processing-dissipation" of the emergency on the road network,which corresponds to the dynamic process of "failure-recovery-normal" of the traffic capacity of the incident link.When the travelers make and adjust their travel decisions,their decisions are generally based on real-time traffic information,and the rationality of their decision-making will be restricted to a certain extent by factors such as road condition information and personal heterogeneity preferences.Therefore,the dynamic change of the capacity of the road link should be considered,and the road network is abstracted into a reactive discrete control system.The time-varying characteristics of the system are analyzed in combination with the link selection behavior of the traveler under sudden environment.And after the dynamic simulation of traffic flow distribution by the Logistic curve,the compression sub-path is was completed.Then the related problems about road network vulnerability transfer under time-varying conditions are discussed.The vulnerability identification method is settled to the application and the road network emergency management under the emergency environment is divided into two parts: the demand side and the supply side.Considering the assessment of the vulnerability status of the road network,it is essentially a representation of the dema nd side of the road network emergency rescue under a sudden environment.Therefore,from the perspective of the supply side(the rescuer),the characteristics of the road network are analyzed.Combined with the random consistency condition and the GERT graph evaluation and review technique,the selection of the rescue routes and the identification of the critical links are completed.After that,through the model comparison and module integration of the previous parts,the Matlab R2018 b software development tools are used to integrate them into a unified simulation environment,which effectively realizes the visualization and practicalization of all the models and algorithms in this paper.The above research work in this paper is expected to serve the theore tical research,road network planning,operation maintenance and emergency management that are related to road network vulnerability,which can provide theoretical basis and technical support for the construction of urban road safety integrated emergency m anagement platform in the future.