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11 July 2017

The Reason the London Underground Gets so Warm

Commuters were on the verge of suffering heatstroke when they used the London underground on 21st June this year.

That Wednesday, which was the warmest June day in over 40 years, was the peak of a scorching heatwave that had devastating impacts across the UK and Western Europe. While people were struggling under the heat of the sun, though, there were others faring much worse in the London underground where temperatures exceeded 35°C.

Considering the generally abysmal weather that the UK suffers with most of the time, a few days of extreme heat during a daily commute shouldn’t seem like too much of an issue. However, more often than not the Tube boasts a rather warm environment, and this isn’t a problem that most underground railways have to deal with. It wasn’t one that London had to deal with either when the Tube first opened back in the 1800s.

That was a pretty long time ago, and that’s part of the problem.

Years of people and machinery giving off heat underground has caused the tunnels to reach their saturation point, meaning there’s nowhere for heat to be absorbed. Due to the lack of ventilation shafts deep down, the heat has nowhere to go but into the walls, and that has caused the average ambient temperature of the earth behind them to rise by roughly 10°C since 1900. While the earth – which mostly consists of heat insulating clay - can still absorb some excess warmth, most of it goes into the surrounding air.

It’s no wonder then that thousands of commuters don’t feel the most comfortable when they travel to and from work every day. The Tube was actually once advertised as a form of travel that was ideal for cooling down, back when the average ambient temperature was only 14°C.

Transport for London is working on several ways to combat the extreme heat underground, including devising more efficient braking systems. Around 89% of the heat generated in the Tube comes from the train itself, particularly from the friction caused by braking, whereas passengers only produce 7% and tunnel support systems contribute the other 4%.

Nothing has been put in place to inspire a major change as of yet, but officials continue to work towards a goal of reducing the heat underground. After all, when it reaches temperatures like it did during the June heatwave, it can pose a serious risk to people’s health.

James Darvill

James is a passionate scriptwriter and reluctant poet with a talent for the dystopian. When he’s not staying up late watching the Simpsons he’s beating the world at Mario Kart, always with a glass of wine in hand.