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

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.

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.

With immediate detection, 1.0 s latency and 1.1 m/s² 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.

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.