Travelling in Extreme Heat

Hot weather can cause the steel rails to expand and buckle

Our network is made up of thousands of miles of steel track. Steel absorbs heat easily and track can get up to 20 degrees hotter than the air temperature. 

When steel gets hot it expands. The rails become longer and start pushing against the pieces of track next to them. This can damage the equipment that detects where trains are and helps us keep trains a safe distance apart. When this happens, we stop trains to keep everyone safe. If there is no room for the rail to expand, the rail can buckle and we need to close the line to fix it before trains can run again. When we stop trains or close a line, this causes delays.

Did you know?

We have hundreds of Extreme Weather Action Teams on standby across the country, ready to respond quickly to fix any problems that might cause delays.

Hot weather can also cause overhead power lines to expand and sag

In hot weather, the overhead lines that provide power to the trains can expand and sag. To avoid damaging the lines, trains must travel more slowly. 
If the overhead lines are damaged, we have to cancel or divert train services until they are fixed. This causes delays for passengers.

Modern overhead lines, which are used on the majority of Britain’s rail network, are much less affected by hot weather. They have auto-tension systems with balance weights or springs that adjust to different temperatures. But older overhead lines have fixed tension and are more vulnerable.

We work hard to minimise delays caused by overheated power lines:

• We adjust the height and tension of our older overhead power lines in summer to help prevent sagging. 

• We sometimes introduce temporary speed restrictions to minimise the force on the overhead power lines. Speed restrictions reduce the risk of damage and keep services running but they can cause delays. We have to balance the inconvenience of delays to passengers against the risk of the greater disruption that would be caused if we need to fully close the line.

• We are replacing old overhead lines with modern, more resilient auto-tension power lines.

Prolonged drought can affect the track

Long periods without rain can mean the ground underneath the tracks dries out and shrinks, creating pothole-like cracks. Much like on the roads, trains can’t run at full speed over these defects and slow down to keep everyone safe.

We work hard to minimise delays caused by drought:

• We may introduce temporary speed restrictions in affected areas to reduce the force on the track.

• We work with train operators to monitor the track closely and identify the need for maintenance caused by drought. Where the soil has significantly cracked, our engineers add more stone to support the tracks and machines realign the rails.

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