It’s so cold in Chicago, crews had to set fire to commuter rail tracks to keep the trains moving smoothly

So Chicago had to start some fires. The process itself is pretty simple: “Get some old rags and other combustibles, soak ’em in oil, lay ’em next to the rail, start ’em on fire,” explained a commenter on the train talk forum Trainorders.com. (Some rail companies use a product called the Fire Snake instead of a diesel-soaked rope.)

During extreme summer heat, rail operators have the opposite problem—metal rails expand and warp, creating a phenomenon known as “sun kinks.”

https://www.citylab.com/transportation/2019/01/polar-vortex-2019-chicago-train-metra-rail-tracks-on-fire/581635/