Even when temperatures plunge to record-breaking lows, Chicago knows how to keep things moving.
As the mercury dropped to -32C at Chicago’s O’Hare airport this week and the windchill sent temperatures down further to -45C, the only way for officials to keep the trains operating was to set the tracks on fire.
Commuters braving the freezing temperatures caught sight of flames sprouting from the railway lines of Chicago’s Metra rail system.
Videos show trains travelling through snowfall as the tracks are being licked by flames.
But, Michael Gillis, spokesman for Metra, assured CNN that the heating system is completely normal.
The flames come from gas-fed heaters that run alongside the rails and keep them warm.
"Anytime it's below freezing were using these," Mr Gillis told the network.
It helps prevent the extreme cold from shrinking the metal and causing the rails to pull apart from each other.
The flames also prevent the railroad switch points becoming clogged with ice and snow in the subzero conditions.
Metra says it's safe to run the trains over the flames because the diesel fuel in the trains "combusts only with pressure and heat, not open flames."
