The TSB's recommendation asks the Department of Transport to "conduct a study on the factors that increase the severity of the outcomes for derailments involving dangerous goods, identify appropriate mitigating strategies including train speeds for various train risk profiles and amend the Rules Respecting Key Trains and Key Routes accordingly."
The CN crude oil unit train that derailed in 2015 was traveling at 38 mph, below the 40 mph limit, and released 1.7 million liters (449,000 gallons) of product when 19 of the 100 tank cars were breached. The crude oil ignited and the resulting fire burned for five days.
TSB pointed to joint bar failures as the cause of the derailment. Undetected fatigue cracks in the joint bars caused failure with the combination of cold temperatures and repetitive impacts from train wheels. TSB said the cracks were undetected due to the assistant track supervisor receiving insufficient training, on-the-job mentoring and supervisory support.
"This accident occurred at a speed below the maximum speed permitted by the Transport Canada approved Rules Respecting Key Trains and Key Routes," said Kathy Fox, chair of the TSB. "The TSB is concerned that the current speed limits may not be low enough for some trains—particularly unit trains carrying flammable liquids."
TSB said the cars involved in the derailment were Class 111 tank cars built to the newer CPC-1232 standard. Although this standard requires the cars to have additional protective equipment, the TSB determined that the speed of the train had a direct impact on the severity of the tank-car damage. Additionally, the lack of thermal protection contributed to thermal tears in those cars located in the pool fire, which led to additional product release. TSB also mentioned the cars displayed similar performance issues as in the Lac-Mégantic derailment.
"The Transportation of flammable liquids by rail has been on the TSB Watchlist since 2014", said Chair Fox. "While stronger tank cars are being built, the current ones will be in service for years to come. The risks will also remain until all of the factors leading to derailments and contributing to their severity are mitigated."