Measures to evaluate post-disaster trip resilience on road networks

Abstract

The resilience of transportation networks, one of the most critical infrastructure in post-disaster situations, will have a significant influence on post-disaster operations, community resilience and business continuity. Consequently, understanding the resilience of transportation networks following a natural disaster is crucial. This research proposes a new Trip Resilience (TR) measure to assess the resilience of trips on road networks following a disaster, integrating all three dimensions of resilience, namely robustness, redundancy, and recovery. The methodological approach includes an analysis of existing transport resilience measures presented in the literature to assess their ability to quantify robustness, redundancy and recovery in terms of the proposed conceptual model. The analytical formulations of the individual component measures are then developed, or adapted from previous research, along with a means of integrating all three into a combined Trip Resilience (TR) measure. A case study methodological approach is then adopted to verify the practicality of the proposed measures using the outcomes from a transportation simulation of a hypothetical Alpine Fault Magnitude 8 (AF8) scenario. A Normalised Trip Resilience (NTR) measure is also proposed that converts the TR to a normalised scale that is easily understandable to decision-makers. Finally, in order to facilitate ranking of the post-disaster impact on districts, a new measure, namely the Equivalent daily number of Impacted Trips (EIT), is proposed. The proposed measure provides an opportunity for decision-makers to estimate and rank the trip resilience between each (group of) Origin-Destination pair(s) using pre- and post-disaster flow and travel time. The resulting measures were capable of being calculated from the outputs produced by the transportation simulation model in the case study, thereby verifying their practicality in real-world situations. The importance of including both robustness (represented by the number of eliminated trips) and redundancy (represented by increased travel time), over the horizon of the post-disaster recovery phase was highlighted. Eliminated trips contributed significantly in areas that were cut off and isolated post-disaster, due to a lack of alternative routes, and increased travel time contributed as more roads were reopened but the alternative routes resulted in increased travel distances and, consequently, travel time.