Abstract

With the help of Under Sleeper Pads (USP) a further step towards a sustainable, and durable superstructure in railway engineering can be achieved. The development of USP within the classic components used in the construction of permanent ways can bring defined elasticity into the track. They are installed on the bottom surface of the sleeper and thereby increase the degree of vertical elasticity in the track superstructure. The objective is to transmit the loads from the vehicles through the rails, rail fasteners and the sleepers into the superstructure and the subgrade in the smoothest, safest and most evenly distributed manner possible. With the use of USP not only the bending line of the rail is activated and the load is distributed to more sleepers but also the contact area of the sleepers with the ballast is widely increased – and vibrations can be mitigated. A normal concrete sleeper shows a contact area of around 2-8% of the sleeper’s bottom area towards the ballast meanwhile the use of polyurethane USP show up to 35 % contact area. Therefore, next to other positive effects, ballast wear will be reduced in a great manner and looking on the sustainability and life cycle analysis the tamping cycles can be reduced up to 2.5 times. Looking back on more than 25 years of USP in track, turnouts and transition zones for ballast protection, improved track stability or vibration isolation, a vast number of projects are evaluated and the long term benefits can be seen in tracks all over the world."br" With the ongoing development of new materials and improvements of the existing products the technology of Under Sleeper Pads is up-to-date and ready to react on upcoming challenges.