Parametric Sensitivity Analysis of Safe Train Interval Model Based on Relative Braking Distance

The magnitude of safe intervals between virtually coupled trains derived from the safe train interval model based on relative braking distance has a great impact on the track capacity planning, infrastructure construction and vehicle design. This study sought to analyze the sensitivity of key parameters affecting these safe intervals, to harness the potential of virtual coupling technology in improving efficiency while ensuring operational safety. The qualitative analysis based on a safe time interval model and the quantitative analysis based on simulations using the model plus an algorithm, were conducted, shedding light on the extent of influence from key parameters in the safe interval model on stopping time differences. The local sensitivity ranking of corresponding parameters was established using the one-factor-at-a-time method (OFAT), namely, from braking rate , response delay, "braking application" stage time to target stopping distance in a descending order. This ranking delineates the range and principle of selecting key parameters and the optimization priorities in safe interval design. In order to make stopping time differences controllable and less than 4 seconds, a 3-stage emergency braking mode was adopted for station approaching, and appropriate typical combination indexes were recommended: the braking rate of more than 1.0 m/s2 for the following train, the response delay of less than 1 s, the minimum safety distance of 2 m and the corresponding target stopping distance more than 4 m. The study results provide the basis for the engineering implementation of virtual coupling.