A Chicago-based transportation company has been intentionally setting fires on train tracks to avoid delays.

During the frigid winter months, when the temperature goes below -1C (30F), this approach is used to prevent tracks from freezing and trains from stop running.

Why? Tracks are affected by extreme cold in two ways.

In some cases, the tracks experience what’s called “pull-aparts.” This kind of rail defect occurs when two rails separate at their connection. The extreme cold shrinks the metal and the rails literally pull apart from each other. Heating the tracks with fire expands the metal until the two rails can be put back together again.

Railroad switch points can also become clogged with ice and snow in subzero conditions, so the heating system is used to unclog them. Maintenance crews light the heaters by hand and can control the flow of the gas. The crew members, working 12-hour shifts, remain in the area when the heating systems are being used so they can monitor the flames.

A few railroad ties are sometimes damaged by the heat, but this method is a lot safer than the one the rail system used to employ to thaw frozen tracks. Crews previously used pots filled with kerosene, stuck them in spaces between the track ties and lit them by hand.

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.”

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