A unified rail-intrusion safety framework for contact avoidance: Integrating exposure control, detection timing, and braking feasibility

OBJECTIVES: Railway intrusion measures are often evaluated separately, although access barriers, detection timing, system latency and braking jointly determine whether person-train contact can be avoided. This study developed the Unified Rail Intrusion Safety Model (URISM) to assess contact avoidance and residual impact speed without transferring road-pedestrian fatality curves to railway impacts. METHODS: URISM combines exposure reduction, condition-dependent detection times, post-detection system latency, emergency deceleration, a stopping-feasibility boundary and Monte Carlo simulation. Available detection distance is measured at the earliest physical detection opportunity, not necessarily at track entry. Four posture-labelled Weibull priors illustrate detection timing; the formulation can also represent lighting, weather, occlusion and sensor conditions. Scenarios examined 40 and 60 km/h at 80 m with earlier detection, lower latency or both. Parameters were illustrative priors, not rail-calibrated estimates. RESULTS: deceleration, the 80 m reference stopping boundary was 44.0 km/h. At 40 km/h with the 2.5 s detection-scale prior, simulated non-zero impact probability was 0.785 at baseline and 0.652 with either timing intervention; combining them reduced it to 0.463 and increased avoidance to 0.537. At 60 km/h, all simulated trials retained impact, although the combined intervention reduced expected residual speed from 52.84 to 47.72 km/h. Initial speed and available distance produced the widest sensitivity ranges within the selected experiment. CONCLUSIONS: In the analyzed scenarios, timing improvements increased avoidance when sufficient stopping distance remained and otherwise reduced residual speed. URISM provides a transparent interface for site-specific detection, response and infrastructure assessments, subject to calibration and validation. These scenario results do not establish operational speed limits or injury probabilities; consequence prediction requires separate railway-specific evidence.