According to the UIC Leaflet Code 720 (Laying and Maintenance of CWR Track), the lateral track resistance (LTR) is the dominant parameter for judging track stability. The minimum allowable radius of the continuously welded rail (CWR) is derived from the lateral track resistance. Thus, a variation in the lateral track resistance has an influence on every national railway regulation referring to the minimum allowable radius of CWR.
During the preparation of the report “Under Sleeper Pads (USP) Recommendations for Use” (IRS 70713-1), the Working Group recognized that no standardised method is defined for measuring the LTR on a single sleeper and the various methods used by the railways lead to different or even contradictory results. In addition, there are several methods for determining the LTR in the laboratory. Thus, it was not possible to assess how the USP influence the LTR.