A framework for resilience assessment of urban transportation systems under seismic hazard

The resilience paradigm is gaining more and more importance across diverse research fields in the recent years, as it reflects how systems adapt to perturbations. The research community increasingly relies on resilience-based design for infrastructures, acknowledging that crises cannot always be prevented. In this context, urban transportation systems (UTSs) represent one of the most critical infrastructures supporting urban functionality alongside systems such as water, energy, telecommunication, and more. These above systems are highly interdependent, with structural assets taking the central role since that transportation networks are designed to connect various city functions efficiently, and thus, any disruption affecting a network element can significantly impact on the operation of the transportation systems. A framework is introduced in this paper that explicitly couples infrastructure damage with the functionality of UTSs and their traffic flows. The proposed framework includes three main components: (i) a supply model of the UTS; (ii) seismic simulations carried out through Monte Carlo samplings; and (iii) a resilience assessment based on various key performance indicators (KPIs). The urban context of Naples, Italy, is used as a case study for the proposed framework, where seismic performance simulations are carried out for two earthquake return periods, i.e., 50 and 475 years, reflecting moderate and severe seismic severity levels, respectively, with different levels of peak ground acceleration (PGA). The findings reveal a significant reduction in the transport network’s capability to retain functional connectivity during severe seismic conditions, whereas the system remains operational and reliable under moderate seismic stress. Moreover, a further analysis specifically focused on hospital accessibility, highlights the critical influence of spatial configuration and directional connectivity on the vulnerability of healthcare infrastructure during high-intensity seismic events. These results underscore the need for resilience-oriented planning, particularly for critical facilities embedded within UTSs. Our analyses specifically focus on seismic hazards, but the proposed methodology remains broadly applicable to other hazard scenarios or different critical infrastructures.