New sander arrangements dramatically reduce impact of low adhesion conditions

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Delays due to leaves on the line could become a thing of the past if the rail industry adopts double variable rate sanders on trains, according to the latest RSSB research.

Sanders are routinely used on trains to reduce the impact of slippery rail head conditions, referred to as low adhesion. By blasting sand between the wheel and the rail, sanders improve the reliability and safety of train services.

New research proves that changing the approach to sanding by introducing double variable rate sanders, which automatically apply more sand when braking at higher speeds, dramatically reduces braking distances.

RSSB undertook a three-month programme of track testing in collaboration with industry partners, at the Rail Innovation and Development Centre at Melton Mowbray using two new Class 387 trains loaned by Great Western Railway.  A robust dataset was created from over 220 test runs covering various configurations of sanders, test speed and train length.

The results show:

  • Using multiple and variable rate sanders improves braking significantly compared with the current fixed rate sander configuration. In particular, using two variable rate sanders can improve stopping distances on a 4-car train by around 50% compared to a single fixed rate sander.
  • Double variable rate sanders provide assured 6%g braking performance. This is an important braking performance measure as it is the basis for timetable planning on most routes.
  • Using double variable rate sanders can reduce SPADs (signal passed at danger) due to low adhesion conditions by 98% including low adhesion station overruns by 96%.

GB rail services were delayed by over 350,000 minutes due to low adhesion conditions last year, causing delays to millions of passengers and freight services. Reliable braking in low adhesion conditions could deliver a significant reduction in industry and wider societal costs associated with poor rail adhesion, which are currently valued to exceed £300M per annum.

By improving the consistency of train braking in low adhesion conditions, double variable sanders are also a key enabler to increasing capacity.

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