Autumn weather can impact railway services, and this is why. 

This year 1.04 million miles of train tracks will be cleared of leaves, according to Network Rail, which is the equivalent of traveling to the moon and back - twice. 

The reason this must be done is because something as seemingly harmless as fallen leaves can have disastrous consequences when they’re met by trains on the railway tracks. 

This was seen firsthand in Salisbury last month, when leaves on the tracks caused a collision between two trains near Fisherton Tunnel. 

But how do fallen leaves actually cause the surface to become so dangerous and how do UK rail services manage this risk?

How do leaves on the tracks cause problems for trains?

The ‘black ice’ of the railways 

When trains pass over leaves that have fallen onto the tracks, the heat generated by the friction between the rails and the tracks as well as the weight of the train itself bakes them into a thin, slippery surface. 

This has been described as the ‘black ice’ of the railway, as this slippery surface is barely visible and can have disastrous consequences. 

Slippery rails can make it hard for trains to accelerate and brake effectively, as there is reduced adhesion to the tracks. 

Delays and longer journey times can be expected in autumn due to this problem as drivers must anticipate the slippery layer of leaves and brake much earlier for stations and signals to make sure they stop in time. 

The double train crash in Salisbury 

In October 31 this year,  the far-reaching consequences of leaves on tracks was seen firsthand when a train slid through a junction near Fisherton tunnel in Salisbury and collided with another service. 

Luckily there were no fatalities, but the driver of the train suffered life changing injuries. 

The reason for this collision was deemed to be reduced adhesion between the train and the tracks due to autumn leaves. 

Problems with train 'tracking'

As well as problems caused by leaves backing onto the train tracks, a build up of leaves can also create problems with tracking trains.

A build-up of leaves between the trains wheels and the electrical parts of the track can cause the train control centre to lose the location of the train. 

This is because the leaves form a barrier blocking electrical signals from between the train wheels and the track. 

When this happens, the trains behind will be delayed until the location of the affected train is confirmed in order to make sure there is a safe distance between trains.

Windy conditions play a part

In autumn, windy weather exacerbates the issue of leaves on tracks as there is more leaf fall over a short period of time. 

This weekend may see delays across the country as a yellow warning for wind has been issued by the Met Office. 

Salisbury is among the areas affected by this warning

How do railway services manage this issue?

The scale of the issue 

Every year thousands of tonnes of leaves fall onto the train tracks from over 13 million trees next to the railway in Britain, according to Network Rail. 

The largest mammal, an adult African elephant, will only weight up to around 7 tonnes, which gives an indication of the amount of debris services railway services across the UK are dealing with.

Reducing the risk - and the vegetation 

Throughout the year, Network Rail manage the trees and plants along the roughly 20,000 miles of railway tracks in the UK. 

This requires keeping the area debris free, sometimes removing trees or vegetation that poses risk, and removing logs and branches.

In autumn, the vegetation management teams target the maintenance or removal of broadleaf tree species that drop leaves such as poplar and sycamore.

Calling in the Leaf busters 

There are 67 leaf-busting trains in the Network Rail fleet which clean the tops of the railway tracks by spraying them with high-pressured water jets.

This removes this slippery leaf mulch film.

To help the train wheels with their grip, the leaf-busting trains also apply a gel which contains a mixture of sand and steel grains.

Network Rail highlights that their routes have numerous leaf-busting teams on-hand 24/7 at key locations across Britain. 

Forewarned is forearmed

Specialist weather forecasters at Network Rail monitor weather conditions and give two updates a day between October and December. 

These updates include estimates of leaf-fall as well as indicating which areas are most likely to need leaf-busting machines.  

Changing to timetables 

The weather, much like the seasons, is something that it is impossible to have control over. 

But it is possible to alter the train timetables to account for this risk, and in areas with very heavy leaf-fall some train operators will publish special autumn timetables.

The autumn timetables have revised journey timings which account for extra time for train drivers to drive more cautiously than at other times of the year.

More can be found out about this issue at Network Rail

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