Measures Of Network Vulnerability IndicatorsFor Risk Evaluation And Exposure Reduction

Reliability of transportation systems can be affected by events both exogenous to the system (i.e. earthquakes, floods, terrorism attack, etc.) and endogenous to the system (i.e. dangerous freight, etc.). Hazardous events can introduce disconnections in transportation systems whose effects can be relevant both in the short term (difficulties in evacuation procedures and aids to population) and in the long term (effects in local services and local economies). For these main reasons, in particular considering nonurban situations, to guarantee an acceptable level of accessibility among urban centers an analysis of network vulnerability is relevant. In this paper, after an introduction concerning the concept of network vulnerability, it is proposed an enhanced method, based on consolidated procedures generally adopted in the analysis of transport networks, to explore a transport network in order to put in evidence weakness in some of the links by computing quantitative indicators. The proposed methodology can be adopted, once defined a risk scenario, both to select where to plan necessary adjustments on transport system and to define adequate operations for evacuation and to come to the aid of population, in order to reduce exposure. An explicative application to a real system is also shown to put in evidence capabilities of the proposed indicators.