Autumnal rail delays could be foiled with dry ice clean-up

Every autumn, an estimated 50 million leaves fall on Britain’s 32,000km of railway tracks. These leaves are compacted by passing trains, forming a smooth, slippery layer and causing the wheels to lose their grip on the tracks.

During this time, trains may travel more slowly over tracks to minimise the possibility of slipping, while service may be reduced to prevent accidents occurring while signalling systems are foiled by leaf contamination. These safety measures cause delays, cancellation, and reduction in services every autumn, costing passengers £345m annually.

Researchers at the University of Sheffield have been studying seasonal rail disruption in collaboration with Icetech Technologies, and are now proposing an efficient and sustainable solution to the problem. This involves an on-board system to assist trains in braking, and a standalone rail cleaning system.

At present, contaminated tracks are treated by applying sand between the wheel and track via an on-board system and through track cleaning with high-pressure water jets (followed by the application of a gel containing grains of sand and steel to increase friction).

The new solution makes use of dry ice (the solid form of carbon dioxide), which is widely used in industry as a cooling agent on account of not leaving any significant residue.  An on-board system applies pellets of dry ice to the track via a powerful jet of air. These pellets rapidly freeze leaves, and then blow them off the tracks as they sublimate and expand into gas, without causing damage to the track or leaving residue. Switching out water jets for dry ice could also improve efficiency by negating the need to carry clunky water tanks across long stretches of track.

The researchers experimented with using dry ice to clean tracks on a low-traffic freight line in autumn last year. They are trialling the technology again this autumn on a wider selection of sites across the UK.

“The solution we have developed is a fully sustainable technology, using the CO2 by-product from other industrial processes,” said Professor Roger Lewis of the University of Sheffield’s Department of Mechanical Engineering. “It will provide more predictable braking and traction than current technology, and will help improve train performance, reduce delays, increase passenger satisfaction and support the use of new technologies to enable greater network utilisation of the UK’s railways.”

The research was funded through a Small Business Research Initiative (SBRI) call, Rail Safety and Standards Board (RSSB), Arriva Rail North, Network Rail and the University of Sheffield.