Air brakes are vital to a train's operation, but the locomotive's engine needs to be running for the system to work.
What happened to the air brakes of the train that derailed Saturday in Quebec will be the subject of much scrutiny by the Transportation Safety Board of Canada.
"The securement of the train at the top of the hill will be one of the major focal points of our investigation," Donald Ross, the TSB's investigator in charge, said in an interview Monday. "The train was left at a location which was higher than the Lac-Mégantic area, and the train rolled down a descending grade into the town. There is an air-brake system and a hand-brake system that are used to secure the train, and we're looking at both those systems and how they performed."
The basic technology for a train's air brakes dates back to 1868, when George Westinghouse invented the system, which would replace the dangerous task of workers who would jump from one moving railcar to another to manually apply the brakes.
The introduction of air brakes was a breakthrough in the rail industry, allowing trains to travel at faster speeds because brakes could be engaged much more quickly than ever before, said transportation policy analyst Greg Gormick.
Hand brakes are also used on individual railcars, or in the Quebec case, tank cars filled with crude oil. Those hand brakes are on each tank car and resemble large steering wheels that can be cranked to put on the brakes when parked.
But air brakes are crucial to a train's ability to safely speed up and slow down. "The engine has to be running for the air pump to be working," said Rex Beatty, president of the Teamsters Canada Rail Conference. The Teamsters union represents thousands of engineers and conductors in Canada, but not at Montreal, Maine & Atlantic Railway. The Maine-based company says its locomotive's air brakes were somehow released during a series of events that led to the derailment.
If the locomotive's engine is shut down, then air is not being circulated to a reservoir. Without air pressure, the brakes "bleed," and the spring-loaded system doesn't function because proper pressure is required to force the air that applies the brakes to the train's wheels, Mr. Beatty said.
"Whenever you leave a train, you must secure it. You have to put on hand brakes and you have to make sure there is continued air pressure," he said. "If there isn't continued air pressure in the brake lines, eventually the air leaks off."
The Railway Association of Canada defended the sector's safety record. "The railway industry and observers believe this is an extremely atypical event," association president Michael Bourque said in a statement Monday. "We wish to reassure North American communities that railway operations are safe and our track record of handling regulated commodities is excellent."