The London Tube has some hot spots.
Crowds and increasing temperatures within the underground train system’s cars have led to almost 3,600 instances of fainting—or cases where passengers felt faint—between January 2016 and May 2018. The National Union of Rail, Maritime and Transport Workers referred to the data as “alarming.”
Most of the faintings occurred on morning commutes, between 8am and 9am. King’s Cross St. Pancras, the rail network’s busiest station, had over 850 faintings during that 28-month time period, according to the BBC. The stops at Green Park and Liverpool Street had the second- and third-highest levels of fainting, respectively.
We faint when our brains don’t receive enough oxygen from blood. When we stand, our bodies have to fight gravity to get blood to the brain. Blood pressure increases as blood vessels contract and the heart rate increases—changes we normally can’t feel at all. When our bodies are trying to keep cool, however, blood vessels dilate to try to get rid of excess heat. If the body is dehydrated from sweating, we may also have less blood circulating in general. A smaller volume of oxygenated blood flowing through open blood vessels means that less oxygen gets to the brain. In an effort to get oxygen to the brain, our bodies hit the panic button and make us go horizontal: We lose consciousness.
Over the summer months, temperatures in the Tube rose to over 35°C (95°F), which is hotter than the maximum temperature for transporting livestock under EU law. Crowding during commutes can make the inside of cars even hotter, while also limiting the oxygen circulating in a Tube car.
Only 40% of the cars have air conditioning, according to government agency Transport for London. There is currently a plan to add more air conditioning units in 2030.