Chicago is currently in the middle of a vicious cold spell caused by rogue Arctic winds. The temperatures, which reached -30℉ (-34 C), have prompted individuals and organizations to take some extreme measures to fight the cold. For instance, Metra Rail, which runs some of the commuter trains in the city, has taken the extreme measure of setting its tracks on fire.
The tracks on fire can be seen in the below video as well as this overhead shot from CNN.
According to Metra Rail, the important thing to note here is that the tracks themselves aren’t actually burning. The flames come from an underground series of gas pipes designed specifically to heat the tracks. Workers light the fires manually and are always on hand to observe in case something gets out of hand.
Trains are able to drive on the tracks while they’re burning because those trains run on diesel, which only burns with both pressure and heat, so it’s safe for the trains.
So why does Metra Rail light its tracks on fire in the first place? There are a couple of reasons, the simplest being that the company needs to clear ice and snow from its switches so they can work properly. Without these flames, those switches would get jammed during a snowstorm and the trains would be delayed.
Another reason for the fire is a phenomenon known as a ‘pull-apart,’ where the tracks actually shrink from the cold and separate. Heating the tracks causes them to expand enough so they can be reassembled.
This specific section of the track is called the A-2 interlocking, and it’s actually the only part of Metra’s rail system that uses these open flames to heat the tracks. Most other sections use either electric heaters or hot air blowers because they’re safer for the metal. But at A-2, the tracks are so close together that these bulkier systems would be impractical, so fire is used instead.
Originally posted on Popular Mechanics