Report: 18 errors lined up to cause Quebec rail catastrophe

The Lac-Mégantic derailment was among the most disastrous in modern North America. Forty-seven people died, some 40 buildings were destroyed and 53 vehicles were demolished when the 63 tank cars and two boxcars derailed and erupted in flames. About 2,000 residents of the community were evacuated.

The Transportation Safety Board of Canada (TSB) listed 18 factors contributing to the disaster, but declined to say whether any were more serious than the others. The accident may have been avoided if any one of the 18 factors were not present, the TSB's Jean Laporte told reporters.

"Accidents never come down to a single individual, a single action or a single factor. You have to look at the whole context," said TSB Chair Wendy Tadros.

Crude oil shipments by rail have increased dramatically in the past decade as oil companies have perfected technologies to extract oil from shale. The increase took a number of people by surprise, including government regulators, Tadros said.

In Canada, rail shipments of oil have increased from a mere 500 carloads in 2009 to 160,000 in 2013. In the U.S., shipments have increased from 10,800 carloads to 400,000 in the same period.

Tadros and Laporte said Transport Canada has taken measures of phase out the use of DOT-111 tankers -- one of three recommendations made in January in an unprecedented joint recommendation by the safety boards of both countries. But they sidestepped questions about whether newer, stronger tankers would have remained intact in the Lac-Mégantic derailment. TSB investigator Don Ross said there are "not enough data points" to determine whether newer tankers would have survived the incident.

The incident occurred July 6, 2013, when an engineer for the Montreal, Maine & Atlantic Railway (MMA) parked the train for the night on a descending grade.