Case study: Under Sleeper Pads

Under sleeper pads (USPs) are cushions which are placed between railway sleepers and ballast. The project as a whole has sustainability benefits in helping reduce carbon emissions and minimising waste through enhancing the lifespan of a rail asset.

Company - Network Rail, Infrastructure Projects track

How was this solved?

The USPs spread the load from sleepers more evenly across the ballast. This reduces the stresses within the ballast layer, extends the life span of the asset and also reduces track maintenance interventions. Ballast is the crushed stone which bears the weight of the rail and helps aid draining. The ballast, formation and sub-grade are critical elements of a rail track bed as they drive the performance of the track.

The overall aim of the USPs is to enhance the lifespan of the railway asset and therefore reduce the amount of materials purchased at more regular intervals.

Typical asset lives without USP are as follows:

  • Rail 15 – 20 years (with half-life re-padding)
  • Sleepers 25 – 40 years
  • Ballast 25 – 30 years (with half-life ballast clean)

Therefore, there is a mismatch between the service life of the ballast and sleepers.

USPs can be used to better match the contact interface between the sleeper and hard ballast, consequently allowing for alignment the life expectancies of the rail components.

The use of USPs would move away from traditional track renewal options, towards a more innovative way of working. 

What were the outcomes?

In terms of environmental aims, the project can help us work towards Network Rail’s Infrastructure Projects sustainable development objectives of:

  • Optimising resource consumption – through enhanced asset life and delivering the lowest asset whole life cost.
  • Lead the rail industry in zero waste to landfill – through reduction in virgin material.
  • Reduce carbon emissions in Infrastructure Projects to help meet the UK target – through reduced maintenance intervention.


  • Carbon smart
  • Reducing our environmental impact

Organisation type

  • Network Rail
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