From Reliability to Resilience: More Than Just Taking One Step Further

Critical systems, such as telecommunication networks, power grids, transportation networks, and supply chains, have been dramatically expanded over the past decades. To avoid significant interruptions of their services, failure-prevention technologies and strategies have been explored extensively. However, in addition to inherent faults and expected failures, such systems are subject to natural and man-made hazards. The frequent occurrences of these hazards result in an increase in the systems' operational uncertainty as well as significant disruptions of their services. Unfortunately, the traditional reliability metrics do not adequately describe a system's performance under such hazards. There is a need for assessing the resilience of a system, which characterizes the system's performance deterioration and restoration under hazards. To date, substantial effort has been devoted to describing and quantifying system resilience from different perspectives. However, conceptual understanding and visionary transition from traditional reliability to resilience are more than just taking one step further. In this article, we briefly review approaches that qualitatively and quantitatively assess system resilience and discuss their applicable scenarios and limitations. Challenges and opportunities in system resilience modeling and enhancement, such as multihazard resilience modeling and restoration sequence optimization, are also presented so that more reliability researchers and practitioners may dive into and contribute to this important area.