The tank cars carrying the crude oil that engulfed parts of Lac-Mégantic in a sea of flames were of an older type that regulators have faulted for years.
Surviving cars that were pulled out of the blast had stenciled markings indicating that they were a type of steel car called DOT-111A in the United States and CTC-111A in Canada.
The 111A cars, which are very common and are shaped like giant beer cans, have been described as prone to puncturing because of their thin metal shells. Over the years, regulators have tried to limit their use, citing their poor design.
Ed Burkhardt, the president of Chicago-based Rail World, Inc., the parent company of Montreal, Maine & Atlantic Railway, the carrier involved in the Lac-Mégantic tragedy, said having a different type of tank car wouldn't have made a difference in the tragedy, where an out-of-control 72-car train barrelled downhill into the town centre and derailed.
"I can't imagine a tank car that's solid enough to withstand what happened here," Mr. Burkhardt told the newspaper La Presse.
However, a safety expert said sturdier tank cars could have meant fewer vehicles catching fire and more time for locals to flee the scene.
"We didn't leave any chance to those people," said Jean-Paul Lacoursière, an associate professor of chemical engineering at the University of Sherbrooke. The Transportation Safety Board of Canada has been warning about the 111A tank cars as early as 1994, after a CN freight train derailed northwest of Sudbury, spilling several tonnes of vinyl acetate.
"This classification of tank car has a high incidence of tank integrity failure when involved in accidents," said the report into the 1994 derailment.
A decade later, a train carrying petroleum products derailed near Quebec City, releasing 200,000 litres of gasoline and diesel fuel into a marshy area.
Concerned that the tank cars were rupturing, even in soft terrain or in low-speed derailments, the TSB asked that higher standards be extended to all 111A models.
The TSB recommendation has yet to be fully implemented however. Transport Canada has acknowledged the deficiency but, according to TSB records, the matter is still being followed up on in meetings and petitions from stakeholders.
In the United States, the 111A tank car has also been described by the National Transportation Safety Board as having inadequate design.
At the same time, the increase demand in crude oil has also increased the demand for tank cars, according to FTR Associates, a consultancy based in Bloomington, Indiana, which specializes in freight analysis and forecasting.
There is now a backlog order of nearly 50,000 tank cars which is expected to keep growing, while the backlogs for all other types of train cars is five times smaller, according to a presentation last May to FTR Associates president Eric Starks.