Getting a Grip: Using Sanders Better

Leaves on the line, and the resulting drop in wheel-rail adhesion, are a perennial problem for railways operating in temperate climates. It has been estimated that the problem costs GB railways over £300 million every year due to lost revenue, performance penalties and the cost of mitigation measures. One of these measures is the use of on-train sanders which spray sand particles onto the rail head when adhesion is low but concerns that this could interfere with the operation of track circuits meant that the use of sanders was heavily constrained.

In 2015, RSSA supported Lloyds Register Rail (now Ricardo Rail) on an RSSB-funded project to decide whether these constraints could be relaxed, and we concluded that they could (see Reducing Risks from Leaves on the Line). This work enabled RSSB to fund a major research project in 2017 which experimented with using multiple on-train sanders and different types of sanders. The results have just been published and are very exciting. 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% and low adhesion station overruns by 96%.

Details are available on the RSSB’s website.

If pilot schemes around the country validate the test findings, this will lead to a dramatic reduction in delays caused by “Leaves on the Line” and significant increases in capacity from by the unfettered implementation of the European Train Control System (ETCS).