Incorporating geographic interdependencies into the resilience assessment of multimodal public transport networks

Severe weather events, such as snowfall, flooding and storms, may affect wide geographical areas and adversely impact discrete transport infrastructure networks (e.g. road, rail) at the same time, thus revealing the existence of geographic interdependencies between these networks. In this paper, we develop two accessibility-based measures to assess the impact of geographic interdependency on resilience based on the concepts of redundancy and substitutability, respectively. These measures are applied to the railway and long-distance bus networks in Scotland. Results reveal that the combined effect of redundancy and substitutability on the accessibility of locations offered by these discrete modes is reduced due to geographic interdependencies, with the extent of losses being positively associated with the spatial footprint of potential events. The results can be used to identify parts of the network where the potential impacts of geographic interdependencies are greatest, and thus require more in-depth scrutiny by network managers.