How to keep subways and trains cool in an ever-warming world

To its credit, TfL has made a lot of efforts over the years to tackle the problem of hot tunnels, including attaching cooling panels to the tunnel walls. The panels, which circulate water to remove heat from the air, were put to use in a trial in 2022, although they are not currently in use. Paul argues that such a system could be very expensive.

Hasan Hamida of the University of Birmingham says the bridge’s water-cooling technology is “a good idea”, although it remains to be seen how much heat it can actually remove from a real, crowded tube station.

Some railroads simply push the boundaries of our ability to cool things down, Hamida says. He gives the example of high-speed trains that, for example, move at a speed of 400 kilometers per hour. They expel air at high speed, which means that the air pressure around the heating, ventilation and air conditioning (HVAC) equipment on the roof of the trains can be significantly reduced. “So you can’t draw air into the HVAC system,” he says. Ultimately, this can cause the air conditioning unit to fail. Hamida adds: “Colleagues from China have contacted me and want to find a solution to this problem.”

However, more and more train operators are using air conditioning systems as standard. For example, the still relatively new London Elizabeth line is air-conditioned. And a spokesman for Skoda Transport, which recently launched air-conditioned metro trains in the Bulgarian capital, says: “In general, every vehicle we produce now is equipped with AC.” Sharon Hedges, chief engagement officer at Transport Focus, an industry watchdog, adds: “As people think about buying new rolling stock, these are the things that should be top of mind now.”

A heat wave in the UK is one thing. How about the Egyptian desert? Germany’s Siemens technology company provides Egypt with a new set of high-speed trains that can travel at a speed of 230 kilometers per hour. The company’s Velaro trains are used in many parts of Europe, but for Egypt, Siemens has really put them through the paces. Last summer, the company took one of the trains to a test facility in Austria and subjected it to harsh conditions, including temperatures above 60 degrees Celsius and high winds. Björn Buchholz, head of air conditioning and door systems, says: “We achieve an internal temperature of 26 degrees in the hottest outside conditions.