The head of the Transportation Safety Board has suggested Canada's rail safety regulations need to be tightened after revelations that a 10-second safety procedure could have prevented the Lac-Mégantic disaster, in which a runaway oil train derailed and exploded in the Quebec town, killing 47 people in 2013.

In its investigation into the tragedy, the TSB said the derailment likely would have been avoided if the engineer had set the train's automatic brakes before leaving it unattended for the night. The automatic air brake is now listed in Transport Canada regulations as an acceptable backup measure for securing a train, though there is much disagreement as to how long it can secure a train for – with estimates ranging from a few hours to a few days.

While the TSB has stated that the automatic air brake "likely would have kept the train secured that night," the head of the federal agency said rail regulations should go further, and only include safety defences that guarantee a train won't run away.

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The primary means of securing a train is with handbrakes, in which the crew turns a handle on each rail car to lock it in place on the track. After the handbrakes, railways are required to use a secondary defence. The TSB said in its report into the disaster that it would like to see only the most reliable physical means of securing a train used in the regulations, which would mean removing the automatic brake from the list of options a crew has because its effectiveness can vary depending on weather and other conditions.

"We called on Transport Canada to require railways to put in place additional physical defences to prevent runaway trains," Kathy Fox, chair of the TSB, told The Globe and Mail in a letter.

"This could mean things like wheel chocks, automatic derails, or modern braking technology. Whatever form this takes, a secondary defence to prevent runaway trains must be a guarantee, and air brakes are not that."

"Air brakes are known to leak. And the rate of leakage is completely unpredictable … Since there are other solutions that are permanent, it is preferable that railways use ones that would ensure that equipment is secured for indefinite periods."

On the night of the disaster, the engineer set the locomotive air brake, known as the independent brake, to secure the train, and also set seven handbrakes. However, when fire crews arrived later that night to extinguish a fire in the locomotive, they shut the engine down, which deactivated the independent brake. Had the automatic brakes, which are air brakes in each individual rail car, been activated that night, the train likely would have held in place since those brakes take a lot longer to leak off.

Some estimates say the train would have stayed in place at least until the morning, when the engineer arrived, and probably for a lot longer, preventing the explosion when the train rolled down a hill and derailed in town.

The Railway Association of Canada dismisses the suggestion that the automatic brake can be relied upon for more than a few hours. In a letter to The Globe and Mail, the president of the industry lobby group called the assertion the train could have been held in place by the automatic brake "highly speculative."

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In his letter, RAC president Michael Bourque asserts that the brakes could not be relied upon for more than two hours. When challenged on that fact Wednesday, on the basis of confidential information provided by a specialist in train securement, Mr. Bourque expanded that time frame, saying the brakes might have lasted six hours or more.

"You can count on air brakes to hold for somewhere around 6 hours – could be longer – it depends on temperature, it depends on a lot of things," Mr. Bourque said. "Yeah maybe it would have secured the train for some period of time, but not definitively, and that's the essential point."

While the industry lobbyist is dismissive of the TSB's claim that the brake could have prevented the disaster, a survivor of the Lac-Mégantic explosion believes the added safety measure could have saved dozens of lives. Even if the accident was only delayed by a few hours – based on the most conservative estimates by Mr. Bourque about how long the brakes can stay activated before the air leaks off – the survivor believes it would have helped significantly.

René Simard said his life would be dramatically different if the train loaded with oil crashed into Lac-Mégantic even a few hours later. He wouldn't have run for his life from the burning Musi-Café bar after the train derailed at 1:14 a.m, because he would have been home in bed – as would have been nearly half of the derailment's victims who were in the bar just before last call. Many of his friends would probably still be alive. The nightmare of fire balls and screams that have haunted the art teacher for the past 2 1/2 years could have been avoided, he said.

"Honestly, the least dangerous time for the train to have crashed would have been around 4 a.m. Of the victims, 26 were in bars when the train struck. Had it happened two hours later, the bars would have been closed and the people would have gone home and would have been sleeping." He said. "The number of dead would have been halved."

Its not clear why the rail industry does not seek to use as many backup strategies as possible to prevent a future accident – from physical defences like chocks, to the automatic air brakes – rather than debating the effectiveness of some methods.

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Mr. Bourque at the RAC believes the automatic brakes aren't worth speculating about. "I agree that had the automatic brakes been set, this would have probably held the train longer," he said.

"What we are saying is that, while it would have helped, we don't know for sure that it would have held for the whole time, given that that train was scheduled to stay in that location overnight."