Analysis of Train Signaling System Safety Distance

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Analysis of Train Signaling System Safety Distance

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Wenjie HUANG / Yanli YAN / Tianhe MA / Gengwei ZHAI

[Objective] The current calculation of safety distance in the moving block signaling system does not consider adverse working conditions such as faults and low adhesion coefficients, resulting in poor authenticity and low precision in safety distance calculations. It is necessary to study the impact of the aforementioned adverse conditions on the safety distance of train signaling systems. [Method] A safety distance model for the signaling system is established to analyze the main factors affecting train safety distance. Considering train braking systems, longitudinal dynamics, and wheel-rail adhesion conditions, MATLAB/Simulink software is used to build a simulation platform encompassing stages such as on-board ATP (automatic train protection) trigger emergency braking, traction cut-off, coasting, emergency braking establishment, and emergency braking. Combining actual train parameters and relevant standards, simulation studies on the safety distance of signaling systems under conditions of ultra-low adhesion, partial loss of braking force in some vehicles, and different train operating speeds are conducted. [Result & Conclusion] Emergency stopping distance is the key factor affecting the safety distance of signaling system and is related to wheel-rail adhesion conditions, the line maximum allowable operating speed, and potential fault types. Under normal conditions with an adhesion coefficient of 0.03 and a train speed of 120 km/h, the safe distance is 1 520.7 m. In the most unfavorable condition (a faulty heavy-loaded vehicle with other vehicles unloaded, 2 bogies removed), the corresponding safety distance is 2 196.7 m. In practical applications, speed measurement errors and positional uncertainties should be taken into account to leave a certain margin for signaling system safe distance and ensuring train operation safety.