Experts reveal why Britain’s rail network grinds to a halt in heatwave

As temperatures across the UK skyrocket, Britain’s public transport network has ground to a halt. 

Rail routes across England, Wales and Scotland are experiencing delays and cancellations, leaving thousands of passengers stranded. 

Frustrated travellers have flocked to X to discuss the issues. 

‘That didn’t take long… “Severe weather” has delayed nearly all departures from waterloo,’ one user wrote, alongside a photo of the crowds. 

British astronaut Tim Peake added: ‘The mind boggles (as the train crawls its way to London) that we can build a space station that, for nearly 27 years, has coped with temperature fluctuations of +121C in the sun to -157C in the shade, 16 times a day, yet the signalling system on SW Trains flops at +30C.’

And one vented: ‘Other countries have hotter weather and I’m sure their train service doesn’t collapse like these lot.’

So, why do trains get cancelled when there’s a heatwave?

Network Rail has revealed how abnormally high temperatures can cause steel rails across the network to buckle.

Britain’s railway tracks cover more than 20,000 miles and are made from steel.

Most of the network can operate when track temperatures hit up to 46°C, according to Network Rail.

This is the equivalent to an air temperature of around 30°C.

However, with temperatures in parts of the UK set to hit 32°C this weekend, we could see parts of the rails start to buckle.

‘When Britain enjoys a summer heatwave, rails in direct sunshine can be as much as 20°C hotter than air temperature,’ Network Rail explained.

‘Because rails are made from steel, they expand as they get hotter, and can start to curve. This is known as “buckling”.’

Network Rail uses remote monitoring systems to keep an eye on its tracks.

When the systems detect that a section of track might be expanding too much and heading towards a buckle, Network Rail introduces local speed restrictions.

‘Slower trains cause lower forces on the track – this reduces the chance of buckling,’ it explained.

Unfortunately, even with prevention measures in place, rails can buckle.

When this happens, the network is forced to close the line and carry out repairs before trains can run again.

‘This can disrupt journeys because we often have to wait until the rail temperature has dropped before we can carry out these essential repairs,’ it added.

Another issue for railway networks amid the heatwave is the risk of overhead wires overheating.

Overhead wires give power to trains by conducting electricity through the pantograph – an apparatus mounted on the roof of the train.

During heatwaves, the overhead wires can expand and sag, causing the train’s pantograph to become entangled in the wires and requiring repairs.

Thankfully, much of the ageing overhead wires have been replaced with an auto-tensioned system, similar to those used European countries with more regular heatwaves, such as Italy.

‘Modern overhead lines, such as those in place on the lines between Norwich, Ipswich, Colchester, Clacton, Harwich, Braintree, Cambridge and London Liverpool Street, and those installed on the Southend Victoria line, do not sag in high temperatures, avoiding the need for precautionary speed restrictions,’ Greater Anglia explained.

One of the key ways that networks prevent tracks from overheating is by painting them white.

Dr John Easton, an executive panel member of the IET’s Railway Technical Network, explained: ‘This can reduce the track temperature by 5°C and reduces signalling failures which lead to significant disruption. 

‘This technique is also used in countries where high temperatures are more commonplace, such as Italy, where engineers often paint the inside faces of the rails white to reflect the sunlight and lower the risk of buckling.’ 

Most tracks across the UK are made of long pieces of rail that are stretched and welded together.

‘There is much less chance of buckling in very high temperatures because there is reduced compression,’ Network Rail added.

‘When a track is made up from short rails bolted together, we leave small gaps between each one so that expansion doesn’t cause a problem.’

Meanwhile, in some part of Britain’s rail network, tracks are laid on reinforced concrete slabs, rather than on sleepers and ballast – a technique often used to prevent buckling in hotter countries. 

While this also helps to prevent damage, it costs about four times as much to install as standard ballasted track.

Worryingly, climate change could increase the frequency and severity of extreme heatwaves, and cause even more chaos for railway networks. 

‘We work closely with many governmental and specialist organisations to prepare our railway for the climate changes projected over the next few years, decades and beyond,’ Network Rail said.