Sander configurations and variable rate sanders

Our research has provided compelling evidence that double variable rate sanders (DVRS) can help end the need for autumn timetables, and allow reliable braking in low adhesion conditions all year round. 

Earlier research had identified the potential safety benefits of using multiple sanders on rolling stock. We followed this up with on-track testing of different sander configurations, using a modern multiple unit in various adhesion conditions. 

Fixed rate sanders (constant sand delivery rate) and variable rate sanders (sand delivery rate varies with train speed) were tested, together with using them at one and two axles. Using a pair of variable rate sanders (at two axles), which became known as double variable rate sanders (DVRS), was found to improve stopping distances on a four-car train by around 50 per cent compared to single axle fixed-rate sanders. They provided assured 6%g braking performance, even in very low adhesion conditions.

Drivers, operators, engineers, suppliers and RSSB then worked together to install DVRS on Class 323 trains. West Midland Trains drivers also carried out a limited number of controlled in-service trials of DVRS during the late autumn period in 2019, adopting harder and later braking than their autumn driving policy. This showed that, with DVRS, it is possible to drive safely in autumn without adopting a seasonal braking strategy.

We are currently supporting the Rail Delivery Group to carry out economic modelling on the benefits of fitting DVRS to various fleets.

Watch our webinar for a full briefing on these important findings.

Alternatives and additives to sand

A knowledge search reviewed alternatives to sand that could boost adhesion, and the case for implementing them in the rail industry.

Higher sand discharge rates provide more adhesion, but have greater potential for track circuit interference. A current project aims to quantify the practicality and benefits of using additives to enhance sand conductivity.