Evaluating urban rail transit vulnerability: A link-centric framework integrating network connectivity and passenger accessibility

Understanding how disruptions reshape network structure and generate heterogeneous accessibility losses is essential for vulnerability assessment in urban rail transit (URT) systems. This study develops a unified link-centric framework that jointly examines disruption-induced structural changes and passenger accessibility consequences under multi-scenario settings. Disruption scenarios are constructed using an interval-based representation that captures structural dependencies under turn-back constraints, ensuring realistic propagation patterns. Passenger impacts are evaluated through an OD-level accessibility classification based on feasible paths and detour thresholds, distinguishing unaffected, partially affected, and fully affected OD pairs. These components are integrated through a composite link-importance indicator that couples network topology with demand distribution, enabling identification of structurally critical and functionally consequential links. The framework links structural fragility with passenger outcomes, supporting more realistic identification of critical links based on structural dependency and accessibility loss. Application to the Beijing URT network shows that vulnerability is concentrated in the southwestern corridor, particularly along the Fangshan Line and southern Line 9, where disruptions cause significant accessibility losses. Targeted structural interventions effectively mitigate impacts, as adding a connection in the vulnerable corridor reduces fully affected OD pairs from 10,565 to 2,470. Sensitivity analysis confirms the stability of identified vulnerable regions under different penalty factors, while validation in Shenzhen and Nanchang demonstrates the framework’s transferability across systems with varying sizes, topologies, and demand patterns. This study provides a unified, demand-sensitive framework linking structural disruptions with accessibility outcomes, offering practical guidance for resilience-oriented URT planning and emergency management.