Urban Road Network Vulnerability Analysis With The Consideration Of Intersection Effect

The main purpose of road network vulnerability research is to identify the weak units in the road network.Quick and effective identification of vulnerable units in the road network is helpful to ensure the stable operation of the road network and the steady development of the social economy.The road network vulnerability research focus too much on constructing evaluation index.While ignoring the real road network features of urban road network and highway network and not to make a clear distinction between them.In this paper,the analysis of urban road network vulnerability will be combined with the characteristics of urban road network.The density of urban road network is high,and there are many alternative paths.The failure of a single road network unit usually affects the traffic flow in the local area.In this paper,the flow redistribution is carried out only within the scope of the local impact,and the traffic demand that needs redistribution in the local influence range is acquired by using method of OD estimation.In the process of traffic redistribution,cascading failures due to the failure of road network units should also be considered.Compared to the highway network,the link length of urban road is not too long,intersection is more.And intersection is the bottleneck of traffic capacity in urban road network,so it has important influence on the operation of traffic flow.But the traditional cascading failure model ignores the influence of intersections on traffic flow.Therefore,this paper will consider the influence of road link and intersection on traffic flow,and improve the traditional cascading failure model of road network.As for the construction of the vulnerability evaluation index of road network,the change rate of trip time is chosen as the evaluation index.The traditional method is to use the change of the total travel time or the rate of change directly,but this method ignores the influence of intersection on the traffic flow.For the city road network,the intersection has an important effect on the traffic flow,so this paper will take the change rate of the sum of the total travel time of link and the total service time of intersection as the vulnerability evaluation index of the road network unit.Finally,a case study is conducted to validate the proposed vulnerability assessment method for urban road network.The results show that the improved cascading failure model and the proposed urban road network vulnerability evaluation index are helpful to improve the calculation accuracy of vulnerability.