USP (Under Sleeper Pads): a contribution to save money in track maintenance

Under Sleeper Pads (USP) are elastic layers which are attached to the underside of sleepers in ballasted track, which influence the properties and the behavior of the rail track. This paper will give you an overview of what was done in the last 2 decades in USP relating to sleeper design, standardisation, economic evaluation and at least real documents of track quality benefits. Austrian Railways (OeBB) launched an international project under the umbrella of UIC to gain more experience under different traffic conditions. In this project the earlier advantages described above were confirmed and experiences from SNCF (French Railways) and DB (German Railways) confirmed the benefits which included High Speed sections of track. The advantages of USP could also be implemented in turnouts. The economic feasibility was undertaken by the Technical University of Graz, Prof. Veit and others such as SNCF and in Innotrack project. In the meantime USP tracks have been in service for more than 19 years and USP are generally used at OeBB as a standard component in their track design. As a result more than 1 million prestressed concrete sleepers with USP and more than 750 sets of turnouts with USP have been installed in OEBB's network. A number of USP could be found also in the networks of DB, SNCF, RENFE, SBB to mention just a few. In the meantime some tracks at Heavy Haul railways are being equipped with USP.