In preparation for the Polar vortex that has now hit Chicago, rail crews set fires to keep trains moving through the Windy City.
A photo posted by Chicago’s railway authority Metra shows employees stand near as bright flames heat up metal near the train tracks.
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If the rails were not warmed up, the extreme cold could shrink the metal and cause the rails to “literally pull apart from each other,” Metra transit posted to Instagram.
While it may look like the train tracks are actually on fire, that is not the case, according to a Metra news release.
“Despite popular belief, the tracks themselves are not on fire,” the release states. “Instead, the flames come from a gas-fed system that runs adjacent to the rail, generating heat on the critical areas where the switches are supposed to make contact.”
Switches are what allow a train to change tracks.
“Winter weather can cause snow and ice to clog switches, which control which rail trains run on,” the Chicago Tribune reported. “Clogged switches can bring trains to a halt until the blockage is cleared.”
Once the metal is warmed up, the rails can be reconnected, according to the Instagram post.
Metra does not just heat up the rails during Arctic temperatures, according to the Tribune. The gas-fed system is kept on once temperatures dip below freezing.
Chicago hit a record low Wednesday morning, ABC7 reported. It was -22 degrees, with a wind chill of 49 below zero, at the airport, the station reported.