Indirect transport cost prioritization index for road networks exposed to natural hazards: Application to earthquake-induced landslides

Natural hazards have historically disrupted road networks, generating significant economic consequences, which are often assessed through reconstruction costs alone. Furthermore, not all road link disruptions contribute equally, as some produce higher indirect economic impacts due to their strategic importance. However, impact models seldom incorporate indirect consequences of road disruptions due to probabilistic events. Therefore, this paper proposes an indirect-cost prioritization index to evaluate the indirect impacts of earthquake-induced landslides on road networks. The index quantifies impacts in terms of increased travel time, canceled trips, vehicle operating costs, gas emissions, and maintenance costs. The index integrates the hazard event probability and the relative contribution of each road segment to the total impact. The methodology is then applied to a case study of New Zealand’s South Island. The methodology is firstly applied to a single scenario, where daily economic losses are calculated across the network at approximately NZD 847,000. Secondly, the variability in economic losses across a predefined set of hazard scenarios is discussed. Finally, the methodology is applied using a set of scenarios to calculate the prioritization index. The case study identified State Highway 6 and State Highway 7 as the top-ranked corridors, reflecting their strategic role in connecting the island and their proximity to the Alpine Fault. Indirect economic impacts were primarily driven by detour-related travel time and vehicle operating costs, which account for over 90% of the total consequences. The methodology offers a tool for road agencies to evaluate impacts of disruptions, prioritize investments, and enhance disaster preparedness.