Britain must “keep ramping up the specification” of its railways to cope with extreme temperatures, the Transport Secretary has said as passengers faced more disruption in the record-breaking heat.

Grant Shapps conceded the UK’s transport network cannot cope with the intense heat, saying that the Victorian-era infrastructure “just wasn’t built to withstand this type of temperature”.

He said such weather events will happen more frequently and insisted “we need to be ready”.

On Tuesday, London Heathrow saw a provisional high of 40.2C – the first time on record that temperatures have reached 40C in the UK.

Mr Shapps has admitted it will take decades to upgrade existing lines to be more resilient.

He told the PA news agency: “Because the spec (specification) has been minus 10 degrees to plus 35 degrees – and we’re now suffering 40 degrees plus – clearly we need to keep ramping up the specification.

“But as new lines go in, as new overhead cables go in, all of that is now spec’d at a higher level than it would have been when those electric cables originally went in.

“We need to drive up the standards. We’re going to see these events more frequently, and as a result we need to be ready.”

The hottest railway track reached a scorching 62C on Monday.

Network Rail said temperatures on rails can rise to 20C higher than air temperature, sometimes causing them to “expand, bend and break”.

All services to and from London Euston were suspended as emergency services were called to a lineside fire caused by overhead electric cables coming down in Harrow.

Network Rail said passenger numbers on Tuesday were around 40% lower than the same day last week.

Overhead electric wires were down in Rugby, Birmingham and Carlisle, leading to a number of trains being trapped and emergency evacuations of passengers.

Network Rail Wales apologised for having to close the Cambrian Line between Dovey Junction and Aberystwyth “due to extreme heat”.

No rail services were running into or out of London King’s Cross on Tuesday, and no Thameslink or Great Northern services were planned to run north of London all day.

East Midlands Railway was running limited services between Derby, Nottingham, Luton, Bedford and London, which were due to stop completely between lunchtime and 7pm – the hottest period of the day.

A spokesperson for Heathrow Airport said things were flowing smoothly, with no major problems despite the intense heat.

London Luton airport’s runway closed for a time on Monday after a “surface defect” was found amid a high of 36C.

Meanwhile, road congestion in several cities was down on last week, figures showed, as people avoided travelling in the heat.

RAC Breakdown spokesperson Rod Dennis said Monday saw breakdown volumes around 8% higher than normal for a Monday in mid-July – down on what they expected, suggesting “drivers are heeding the warnings and only setting out if they’re confident their vehicles won’t fail them”.

Police described a section of the A14 dual carriageway in Cambridgeshire as looking like a “skatepark” after it warped in the heatwave on Monday.

The westbound section of the A14 at Bottisham was closed overnight on Monday into Tuesday for emergency carriageway repairs, with a National Highways spokesperson explaining that it was an older road surface and that they “do not anticipate any further significant issues”.

Mr Shapps said issues on the rails and roads will continue for decades during extreme heatwaves.

Asked how long it will take to upgrade existing rail infrastructure to be more resilient, he told Sky News: “Decades, actually, to replace it all.

“Ditto with Tarmac on the roads.”

He told BBC Breakfast that the UK’s infrastructure “much of it built in Victorian times, just wasn’t built to withstand this type of temperature”.

Asked if the transport system can cope with the weather, he said: “The simple answer at the moment is no.”

Transport for London (TfL) said around 1.03 million entries and exits were made by London Underground passengers up to 10am on Tuesday – down 30% compared with the same period last Tuesday, and also lower than Monday’s figure of 1.06 million.

Some 1.04 million bus journeys were made up to 10am, a decrease of 16% week on week, and down from Monday’s figure of 1.07 million.

RAF Brize Norton will remain closed amid extreme heat on Tuesday, with an inspection and assessment due to be carried out later and again on Wednesday morning.