Britain is set to experience its hottest day on record this week, with forecasters predicting astonishing temperatures of up to 41C (105F) in parts of the country.
Transport links are at a standstill amid the unprecedented heat and many commuters are facing train cancellations this morning.
So why are heat waves disrupting rail transport?
network rail has shown how abnormally high temperatures can cause steel rails to buckle throughout the network.
“When there is a summer heatwave in the UK, rails can get up to 20°C in direct sunlight [36°F] hotter than air temperature,” it declared.
“Because rails are made of steel, when they get hotter they expand and can start to curve. This is referred to as “buckling”.’
Network Rail has demonstrated how abnormally high temperatures can cause steel rails to buckle throughout the network
Transport links are at a standstill amid the unprecedented heat and many commuters are facing train cancellations this morning
Britain’s railway tracks stretch for more than 20,000 miles and are made of steel.
Most of the network can operate when track temperatures reach up to 46 °C (114 °F), according to Network Rail.
This corresponds to an air temperature of around 30 °C.
However, as temperatures soared to 41°C (105°F) in parts of the UK, we could see parts of the rails beginning to buckle.
Network Rail uses remote monitoring systems to keep an eye on its tracks.
When the systems detect that a section of track may be expanding too much and heading for a curve, Network Rail imposes local speed limits.
“Slower trains cause less forces on the tracks – this reduces the chance of jackknife,” it explained.
Unfortunately, splints can buckle despite existing preventive measures.
In this case, the network is forced to close the line and carry out repairs before trains can run again.
“This can disrupt rides as we often have to wait for the track temperature to drop before we can make these vital repairs,” she added.
Another concern for railway networks amid the heatwave is the risk of overhead wires overheating.
Overhead wires provide electricity to trains by passing electricity through the pantograph – a device mounted on the train’s roof.
During heat waves, overhead wires can expand and sag, causing the train’s pantograph to become tangled in the wires and require repair.
Luckily, much of the aging overhead wires have been replaced with an automatically tensioned system, similar to what is seen in European countries with more regular heat waves like Italy.
One of the main ways networks keep tracks from overheating is by painting them white. This ensures that the chains absorb less heat and stretch less, reducing the risk of buckling
The Met Office has put in place a red alert as temperatures are expected to reach 41C in parts of the country
“Modern overhead lines, such as those installed on the routes between Norwich, Ipswich, Colchester, Clacton, Harwich, Braintree, Cambridge and London Liverpool Street and on the Southend Victoria Line, do not sag in high temperatures and avoid the need for precautionary speed limits”, declared Greater Anglia.
One of the main ways networks keep tracks from overheating is by painting them white.
dr John Easton, board member of the IET’s Railway Technical Network, explained: “This can reduce track temperatures by 5°C and reduce signal dropouts that cause significant disruption.
“This technique is also used in countries where high temperatures are more common, such as Italy, where engineers often paint the insides of the rails white to reflect sunlight and reduce the risk of warping.”
Most railways across the UK are made up of long lengths of rail that are tensioned and welded together.
“At very high temperatures there is a much less chance of warping because there is less compression,” added Network Rail.
“When a track is made up of short rails bolted together, we leave small gaps between the rails so expansion isn’t a problem.”
Some parts of Britain’s rail network are now laid on reinforced concrete slabs rather than sleepers and ballast – a technique often used to prevent warping in hotter countries.
Although this also helps to avoid damage, it costs about four times as much as a conventional ballasted track.
Worryingly, climate change could increase the frequency and severity of extreme heat waves and wreak even more havoc on railway networks.
“We are working closely with many government and industry organizations to prepare our railroad for the climate changes projected over the next few years, decades and beyond,” Network Rail said.
Why is it so hot in the UK this week?
The UK could experience its hottest day on record today, with temperatures reaching 41°C (106°F).
But why is the country in the midst of such an oppressive heat wave?
Experts say this is due to a number of factors, including winds blowing hot air up from North Africa and the Sahara, the subtropical ‘Azores High’ pressure system creeping further north, and the ongoing effects of climate change.
It has led to this met office Red extreme heat warning issued for much of England today and tomorrow, with health officials declaring a ‘national emergency’.
There are fears that hospitals will be overwhelmed, schools will have to close and transport links will be at a standstill due to canceled trains and melted roads.
London is expected to be one of the hottest places on earth as temperatures soar above those in Western Sahara and the Caribbean. The current highest temperature in the UK is 38.7 °C (101.7 °F), recorded in Cambridge in 2019.
Part of the reason for the hot weather is a pressure system called the Azores High, which usually drops Spainhas grown larger and is being pushed north.
The Azores High is usually to the south but currently lies directly over Great Britain and Ireland and extends from the Azores Islands
This has brought scorching temperatures to Britain, France and the Iberian Peninsula.
The high pressure near the southern half of Britain that has been responsible for recent warm weather continues to dominate over us.
As this develops, it triggers heat waves that can also bring what are known as “tropical nights” – when night-time temperatures do not drop below 20°C (68°F).
These heat waves are becoming more likely and more intense due to climate change.
Meanwhile, winds turned south late last week, bringing hot air from North Africa and the Sahara and allowing Britain to take advantage of some of the 113F (45C) heat from Spain and France.
