Transportation security and mobility often conflict with each other. An open and accessible system provides for the efficient transportation of people and goods; however, this openness also allows malicious entities to exploit the transportation system as a target, weapon, or means to reach another target. Security actions taken to prohibit malicious entities from reaching their targets or to capture them after an attack may degrade the transportation system. Security also may cause the entities to adapt their methods or targets, creating more complex analysis requirements. This paper incorporates two types of substitution (method and target) into a methodology to determine the risk profile for the transportation system due to attacks on the transportation system itself, collateral damage to the network due to targeting of adjacent assets, and pre-event and post-attack security measure implementation. Monte Carlo simulation generates scenarios of target, attack methods, intelligence, security, substitution, target failure, and damage to the transportation network. Risk is then characterized through a profile of scenario likelihood and consequences. Application of the methodology to a hypothetical network with 5000 iterations revealed one instance of no targets being selected and, although scenario probabilities were very small, 18% of the cases resulted in the complete disconnection of the origin and destination pair. Thus, the citys decision makers should carefully consider security measures in conjunction with the attacks if post-attack evacuation is a potential action.
Abstract