It's a familiar sight at this point for Chicago area residents, but it's still a fascinating sight as railroad workers build bonfires along the tracks during periods of cold weather.
Subway workers did just that on Monday, lighting fires in the afternoon and into the evening after a long stretch of cold weather in the area.
So why do workers light small fires along the tracks?
To be precise, the tracks themselves are not set on fire. Fires are actually lit to help fuel gas-fired heaters at various points along the tracks, especially near electrical switches.
Metra workers were seen setting fires along the tracks on Monday, and here's why
These heaters must be manually ignited and are intended to help melt ice that builds up and freezes on switch components and tracks.
This ice can not only cause wheels to slip on the tracks, but it can also cause switches to operate more slowly or even stop working altogether, causing widespread delays for trains waiting for switch clearance to direct them onto their correct tracks.
According to Popular Mechanics, snow can disrupt the flow of electricity that allows switches to operate, meaning trains must slow down or even stop completely to allow switches to move.
Even with the fires, there were still plenty of switching issues on Chicago-area railroad tracks Monday, with air temperatures still below zero and wind chills dropping to between 20 and 30 degrees below zero.