Securing linked transportation systems: economic implications and investment strategies

The security of the transportation system depends on that of any of its components and how they are interlinked. But the securing of each component is oftentimes in the hand of the agency in whose jurisdiction it falls. Literature on reliability and security economics suggests that when security is defined by the weakest link in an interlinked system, then its level is determined by the agent with the highest cost-benefit ratio, and the other agents have the tendency to under-invest or free ride. When security is a function of total effort, then the opposite obtains and the reliability will depend on the agent with the lowest cost-benefit ratio. These conditions arise in urban transportation. This research explores agency investment behavior in multi-agency urban transportation systems develops guidelines for investments in security. The question to answer: is it preferable to let each agency operate its own security budget and make its own investment decisions or is this process better centralized?