Leaves on the Line : Wrong Kind of Snow

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These have been the sorts of headlines that have greeted rail travellers from the mid-Autumn to early Spring, every year on Britain’s railways, and back in the days when it was just British Rail, the target for complaints and abuse was just one organisation. Today, and coming in the next 8 weeks perhaps, the same problems will doubtless occur, and delays, cancellations and complaints, along with tempers no doubt, will rise.

But, are we any further forward? The answer is yes and no – obviously!

Recently, a research paper was published identifying the tannin in leaves that mixed with the damp conditions at the railhead, and in Network Rail’s words – are “the black ice of the railway”. This in certainty will reduce friction between rail and wheel, and loss of traction. The problem, is how to remove it, and increase the adhesion levels.

This was how the media ‘broke’ the story at the end of July.

Guardian headline

Back in steam days it was, to some degree, rather more straightforward perhaps, mixing steam and sand directed at the interface ahead of the wheels as they made contact with the rail was a simple option – not infallible, but an option. Of course, that process continues to this day, as the ‘standard’ method – but improvements were and are essential.

In 2018 the University of Sheffield offered a possible solution to the leaves on the line question with an innovative idea using “dry ice”, in a trial, funded by a grant from Arriva Rail North, which led to further trials on a number of passenger lines during autumn 2019.  Working together with a Sheffield business – Ice Tech Technologies – the process was tested on little used freight lines, in sidings at depots, and later, at other locations. This is a video showing the basic elements of the process:

Fascinating, but perhaps still some way to go.

The CO2 used, is a by-product of other industrial processes, and unlike the conventional railhead cleaning and sanding, does not leave a residue on the rail head. The track cleaning trains do not have to carry 1000s of litres of water, and longer distances can be treated.

Overall the process is intended to provide improved traction and braking control.

At the heart of the challenge posed by leaves, is that layer of ‘black ice’, which in autumn and winter causes so much passenger misery and operational problems. Now, back in Sheffield, the university’s renowned skills and knowledge have identified the cause – and the answer seems to be ‘tannin’, which is present in the leaves falling from the lineside trees every year. These large molecules seems to be the key ingredient that leads to the formation of the compacted layer on the surface of the rail, providing that unwanted reduction in friction at the rail-wheel interface, in turn leading to traction and braking.

Network_Rail_plant_at_Dereham

Network Rail Windhoff Multi-Purpose Vehicle DR98910/60 at Dereham in May 2008.      Photo: DiverScout at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6802613

The railway environment provides many challenges in actually running changes as environmental conditions change over the year, but in Britain, winter especially has been the cause of many train cancellations and delays. Nowadays, the operation of trains and signalling systems are ever more dependent on security of communication – be that signalling centre to train, or track to train – and the on-board systems and traction drives are equally prone to the impact of our changeable weather.

Back in the 1980s, there was a famous, and often-repeated phrase used by a British Rail spokesman to respond to a journalist’s question about snow, train delays and cancellations. That remark: “the wrong kind of snow” was as historic as the BBC weatherman’s observation that a hurricane was not going to happen – and then it did, and Sevenoaks became Oneoak!

The “Wrong Kind of Snow” remark prompted me to write an article in Electrical Review looking at how the UK, dealt with extreme weather conditions, and compared these to how our near neighbours, in continental Europe managed these events. The full feature is as shown below – click on the image to read in full.

Wrong Kind of Snow3

Let’s hope these discoveries abojut tannins and the new techniques for keeping the rail head clean will work to better effect, and reduce the impact of leaves on the line in the coming months.

-oOo-

Useful Links & Further reading:

Ice Tech Technologies Ltd

Rail Innovation & Technology Centre (RITC) at the University of Sheffield

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