In the Rocky Mountains of Canada earlier this week, a train derailed, killing three, after the brakes failed due to extreme cold.

According to globalnews.ca,

A Vancouver-bound train with 112 grain cars was parked with its air brakes engaged on a grade east of Field, B.C., when it started moving on its own around 1 a.m. Monday. The train sped up to well over the limit before 99 cars and two locomotives hurtled off the tracks. It was about -20 C at the time.

Engineer Andrew Dockrell, conductor Dylan Paradis and trainee Daniel Waldenberger-Bulmer died in the crash.

The white paper said cold increases air leakage from a train’s air-brake system that results in varying air pressures between the head and tail end of a train.

“This is a major challenge.”

Trains are shortened when temperatures dip below -25 C to ensure pressure remains consistent throughout their entire length, the report said.

The crash spurred a new requirement that all trains use hand brakes.

Canadian Pacific released a white paper on railroading in extreme cold with additional details.