Metro Heat

A friend from the U.K. told me that the rubber tires (tyres) on the underground trains help stabilize the cars, making the ride much smoother. The tires are configured both vertically, in contact with a flat ledge running in parallel to the metal rail on which the actual steel wheel of the metro comes into contact, as well as horizontally, in contact with another flat ledge running also in parallel but perpendicular to the first ledge.

The real purpose of my friend's story was to complain about how hot it is in the metro stations. He told me that the friction from all those tires (at least ten per car) generates a lot of heat, which is why you sometimes feel like you are in an oven down there.

I've written about this elsewhere, but it is really hot in the summer in the metro but also in winter because you tend to be bundled up against the cold that is outside. But you have this 'interlude' where you go into a really hot crowded place where it would be quite difficult to shed layers only to have to put them back on again when you hike up the long stairs or escalators to go back out into the cold and blowing snow.