Assessing Risks to Inform Resilience: a Criticality Assessment of the British Railway Network

National infrastructures are constantly at risk from extreme weather events and random shocks that induce widespread failures across such systems. For example, the vulnerability of Britain’s national-scale rail infrastructure has been highlighted during extreme floods, and it seems likely that the levels of risk faced by transport infrastructures more generally will increase in future years. Given the importance of rail infrastructure, there is a clear need for an improved understanding of the risks which it faces. Such a risk assessment would aim to identify the relative criticality of the network elements which different risk events are likely to affect, leading towards better risk management and resilience investment decisions. This paper provides a methodology to meet this need, by analysing the systemic risk to Britain’s rail infrastructure from a range of disruptive events. It first considers the range of events and processes which have the potential to disrupt operation of the rail network. Alongside this, a procedure is developed for assessing the relative criticality of different nodes and edges on the network based on the passenger traffic they carry. Two case study risk types (floods and traction system failures) are used to demonstrate how criticality assessment can identify those parts of the rail network which are most at risk of causing substantial disruption to rail traffic, and therefore are most critical to maintaining national mobility. The paper concludes by considering the implications of this analysis for investment decisions and the potential for transferring this methodology to other spatial or economic contexts