Several local reports on Tuesday showed rail crews using fire to heat up railroad tracks to ensure trains can run smoothly and without incident. The rail, which is used both for commuter travel and commercial cargo, is critical not only to Chicago, but also businesses across the United States. And when temperatures get well below freezing, the cold can cause bolts to erupt from the rails. Cold temperatures can also stop switching points on rails to work properly.

According to ABC News, crews discovered on Tuesday that some of those switching mechanisms were not working properly, despite having devices that are designed to stop them from freezing. In response, crews were forced to soak rope in kerosene and place it against the rails to warm them and allow for proper operation. The technique is used to fix rails when they become damaged from the cold.

Not surprisingly, the scene of railroad tracks set ablaze caught some people in Chicago by surprise. But it turns out, in temperatures of extreme cold, it’s the best way to keep trains moving.

It’s so cold in Chicago, crews had to set fire to commuter rail tracks to keep the trains moving smoothly. https://t.co/ccrTwwwO6C pic.twitter.com/av7o5opEQ8

— ABC News (@ABC) January 30, 2019

Still, in light of the bitter cold, Amtrak isn’t taking any chances. The organization on Wednesday has canceled commuter train service due to the cold. As of this writing, Chicago’s temperature is 20 degrees Fahrenheit below zero. Wind chills of between 50 below zero and 60 below zero are expected.