Temperatures in Subways Can Soar Well Above 100. What Some Cities are Doing About it.

When summer temperatures soar, the interior of subway cars and underground stations can get unbearably — and dangerously — hot, writes Chris Baraniuk in Wired.

As Baraniuk explains, “Trains, being metal tubes packed with people, are hard to cool down.” U.K.-based researcher Jonathan Paul has an idea for cooling the London Tube, where he has measured temperatures of up to 107.6 Fahrenheit. “He’s working on a technology that would use groundwater at roughly 10 Celsius to ferry excessive heat away from underground stations.”

More transit agencies are adopting train cars with air conditioning, but some trains, including some in China, are so fast that HVAC systems can’t function effectively. In Egypt, trains are equipped with a special filter system to remove the sand and dust that batter trains in the desert. 

Other ways to cool trains include reflective paint that keeps cars cool when exposed to sunlight and awnings to shade trains at stations. But with public transit budgets facing growing shortfalls, upgrades like air conditioning and cooling methods will likely have to wait until agencies can afford to replace their rolling stocks.