Speed limits on railways over track buckling fears

Railway speed restrictions have been brought in across most of England and Wales as record temperatures could affect the safety of steel tracks.

Trains will mostly be limited to speeds of 90mph, down from 100mph or 125mph, while some will go as slow as 20mph.

The Met Office has issued a red extreme heat warning in England, with amber warnings in Scotland and Wales.

When steel gets very hot it expands and tracks can bend, flex and, in serious cases, buckle, Network Rail said.

It advised only essential travel and warned journeys would take significantly longer than usual with more chance of cancellations.

Those who do travel are advised to wear cool clothes, take handheld fans and ensure they have plenty of water, it said.

Many train companies will be running reduced timetables and passengers are being advised to check before they depart.

Speed limits are brought in when temperatures soar as steel railways absorb heat easily and tend to be around 20C (68F) above the surrounding air temperature.

The restrictions help because a train exerts less force when it's going more slowly, meaning the rail is less likely to buckle in the heat.

Overhead power lines - especially less modern ones - can also expand and sag in hot weather, and so travelling slower reduces the risk of damage.

Jake Kelly, who is leading the management of disruption for Network Rail, told BBC Radio 4's Today programme the railways would be placed in come under "exceptional stress" due to the heat.

Mr Kelly said the rail operator hadn't taken its decision to reduce services lightly, but added "we have not been faced with these exceptional temperatures before".

"Our advice very strongly to customers in England and Wales today and tomorrow is to only travel if absolutely essential," he said.

Mr Kelly said he hoped usual service would resume on Wednesday.

Services on the West Coast Mainline will be limited to 90mph, with operator Avanti West Coast warning there would be "far fewer" journeys on Monday and Tuesday.

"Customers with advance tickets for travel on Monday 18 and Tuesday 19 [July] who choose not to travel are entitled to a full refund via their point of purchase," the company said.

"Alternatively, tickets will be valid for travel up to Wednesday 20 July."

Meanwhile, the East Coast Mainline between London and York and Leeds will be closed between 12:00 and 20:00 BST on Tuesday. It is because the line is more susceptible to high temperatures than others, for reasons including the design of the overhead electric wire supports.

In other areas, which includes journeys out of King's Cross station in London, trains will be limited to 60mph between 12:00 and 20:00 BST, meaning a normal two-hour journey will take more than four hours.

In a bid to try and stop tracks getting too hot, Network Rail paints "hot spot" sections of track white so they absorb less heat.

Network Rail's extreme weather action teams, or "EWATs", will be based at key hotspots, monitoring trackside temperatures and responding to any potential issues caused by the heat.

Mr Kelly said Network Rail was spending "hundreds of millions of pounds a year on making the railway more resilient but ultimately faced with weather like we have never faced before the infrastructure will suffer".

He also said one reason services had been reduced was due to modern carriages having no windows which can be opened.