New track shift safety limits for high-speed rail applications

Track shift is defined as the permanent lateral distortion of a track segment due to high vehicle induced lateral loads. Excessive track shift can lead to unsafe conditions leading to ride quality deterioration or vehicle derailment. Current track shift standards used in Europe and the USA minimum high speed safety standard are outlined. It is considered necessary to review these standards on the allowable net axle lateral to static vertical load limits in the light of new technical developments and requirements. A Track Residual Deflection Analysis model (TREDA) was developed which considers single or multiple axle loads, net axle lateral loads at single or multiple axles, and net axle lateral loads varying sinusoidally. Successful validation tests for the model were conducted at the US DOT Transportation Technology Center. The safety criteria for track shift mitigation are based on the requirement that lateral loads generated by high-speed vehicles operating under maximum speed, cant deficiency, thermal load, and initial line defect conditions should not produce any permanent lateral track displacements. The results of the model were compared with those of the Prud'homme formula, which was found to be conservative. New safety limits are recommended.\n