The main objective of the project was a standardization of a ballast superstructure with Under Sleeper Pads (USP) in order to enable all UIC Railways to benefit from the advantages of USP within as many fields of applications as possible.
- Costs/Superstructure: Working out the positive influence of using USP when it comes to saving costs during construction, renewal and upgrading of railway lines without any disadvantages concerning track availability and life-cycle-costs
- Costs/Substructure: Investigating the influence of using USP in situations with inhomogeneous subsoil with regard to track availability, life-time and costs
- Special Applications: Thoroughly assessing the benefits of USP for the use in transition areas, on short bridges, in small-radius curves and for turnouts and extension joints
- Vibrations: Investigating the benefits of using USP as a protection against vibrations, structure-borne noise and air-borne noise
From 2005 to 2007 the USP project team compiled and investigated the effects of USP. The group’s work comprised laboratory tests, theoretical calculations and practical track measurements.
Positive effects of USP, confirmed in test sections are:
- Improvement of the initial track geometry quality and of the deterioration rate
- Reduction of structure-borne noise and vibration
- Reduction of long pitch corrugation in tight radius curves
- Reduction of maintenance efforts; possible stretching of Leveling Lining and Tamping (LLT) periods
While the influence of the sleeper design has not been discussed, the possibility of reducing the ballast depth has also been retained.
The tendency to obtain the following benefits from USP has been considered:
- Compensation of locally inhomogeneous conditions: E.g. transitions between different construction types, between embankment and bridges as well as at level-crossings.
- Reduction of high-frequency vibration and structure-borne noise – USP as an alternative to under ballast mats (UBM) in the frequency range above 40 – 50 Hz
In order to improve the track geometry quality some railways have already introduced USP as a standard solution for special cases of applications within their networks.
The reports for the six work packages and the final report of the project were published in 2007.