New track shift safety limits for high-speed rail applications

The analytic development of the fundamental mechanics of track lateral shift due to vehicle and thermally induced loads for the determination of "allowable limit" loads on the track to prevent progressive lateral shift was presented in an earlier work [1]. This paper presents the results of a follow-on study on improving and validating the model, and applying the analytic and experimental results to the development of new track shift limits for high-speed rail applications. Specifically, this paper reviews current European and US standards for track lateral shift, provides a description of the TREDA analysis model to predict residual track lateral deflections under multiple axle passes, discusses results of recent model verification studies based on field tests at the US DOT’s Transportation Technology Center, and applies the model to develop elastic limit based (Prud’homme type) “allowable lateral loads” to prevent excessive lateral shift. It is shown that for a set of fixed track parameters these allowable loads are dependent on curvature, thermal load, vertical axle loads, and on the nature of the lateral forces generated (i.e. constant versus variable). Parametric studies show that the classical Prud’homme limit tends to be conservative. Additionally, the paper presents a prototype system for monitoring in-service net axle lateral forces through wayside and vehicle borne instrumentation. The work presented here is part of the US DOT/Federal Railroad Administration’s research efforts to develop the technical information required to establish “safe” operating practices for high-speed rail service.