Source: Adapted from Linkov, I. and J.M. Palma-Oliviera (eds) (2017) Risk and Resilience, Amsterdam: Springer.
For a transportation system, resilience is the capability to recover from a disruption to an operational level similar to before the disruption in a timely manner. The longer and deeper the impact of the disruption on operations, the less resilient a transport system is. There is a wide range of possible disruptions ranging from anthropocentric to natural, from local to global. For instance, a local natural disruption would be a thunderstorm impairing road and airport operations for a few hours. Since infrastructures are not damaged, recovery is a simple matter of the weather event ending. Much more severe would be a hurricane forcing the closure of ports, airports, bridges, and transit systems for several days with damage to infrastructure such as power distribution systems. In this case, recovery is a matter of inspecting and repairing infrastructures, which may take several weeks, depending on the damage and the availability of labor and equipment.
Resilience and efficiency are usually on the opposite side of the spectrum. An efficient transport system is commonly less resilient, even if every transportation network has a built-in level of resilience. From a transportation perspective, an efficient network is structured around high-capacity routes with a few links. A resilient network would be composed of more connections enabling alternative routes.
From a supply chain perspective, efficiency is associated with lean practices (just-in-time) with limited inventory levels, distribution centers, and a few strategic suppliers. A resilient supply chain carries a higher inventory level, including stock buffers at intermediary locations and a reliance on a larger number of suppliers. If a part of the supply chain is disrupted, it is expected that other segments will be available to compensate.
A risk for transportation systems and supply chains is that planners and operators are prioritizing efficiency with the expectation that disruptions are uncommon and random. The built-in resilience of an efficient network or supply chain is assumed to be sufficient to cope with the most anticipated disruptions. Climate change would increase the risk of disruptions of transportation infrastructures in manners that are difficult to predict.