As the polar vortex covers the Chicago area with life-threatening low temperatures this week, rail crews are literally adding to the heat to keep the trains running.
The Metra is using a system that runs along rails to generate flames and heat to prevent rust and exchange defects from extreme cold that could disrupt the train service.
"Separations are rail defects in which two rails separate in their connection," the railroad said recently in a post on Instagram. "They occur in extreme cold when the metal shrinks and the rails literally separate from each other."
Once the metal is heated and expanded, teams can then reconnect the separate rails, according to Metra.
THE DEAD POLAR VORTEX UNDER INTERVAL WITH COLD RECYCLING, PREVIOUSLY ACTION TO MINIMIZE TALKS OUTDOORS
While it may seem to the passengers on a train and in the photos that the rails are on fire, Metra says that's not really the case.
"Despite popular belief, the banners themselves are not on fire," the agency said in a statement. "Instead, the flames come from a gas-fed system that runs alongside the rail, generating heat in critical areas where the switches should contact."
Metra uses the system to help keep the switches clear and go from "fail-safe" mode, which Metra explains when the switches do not come into contact with the rail and complete an electrical circuit. This cuts off all train traffic around the area.
"The winter weather will always be a challenge for the railroad and although no railroad is free of exchange problems, innovations like A-2's switch heaters help alleviate some of these obstacles," the railroad explains.
The practice is not only used during extreme Arctic climatic events, but whenever the temperature falls close to zero.
VORTEX POLAR CAUSES THE CHICAGO RIVER TO SMOKE, FREEZE AS SUBZERO TEMPERATURE
In Chicago, temperatures still dropped after a negative fall of 19 degrees, breaking the previous record of 1966, although the cold north wind in Illinois had a temperature as low as minus 57 degrees.
About 1,300 flights canceled Wednesday in Chicago were at O & Hare International Airport, one of the busiest in the country. Governors from Illinois, Wisconsin and Michigan declared emergencies to be the worst threat of the cold on Wednesday.
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At least six deaths were linked to the weather system on Tuesday, including a man hit and killed by a snowplow in the Chicago area, a young couple whose SUV hit another on a snow road in northern Indiana and a man Milwaukee found frozen in a garage. Two other people were found frozen to death in Michigan.
The Associated Press contributed to this report.