An investigation report released Tuesday into the derailment of a CN freight train near the community of Cariboo, B.C., between Prince George and Endako, blames a broken wheel for the accident, which saw 19 cars carrying coal go off the tracks.
A similar train derailment occurred along the same line near Fort Fraser, B.C., in February 2011.
The board issued a safety advisory at that time, warning that Transport Canada has no regulatory requirements for wayside inspection systems and should review inspection criteria — a suggestion repeated Monday.
"When car maintenance policies allow for increased flexibility for maintenance level wheel impacts ... there is an increased risk of in-service wheel failures, especially during winter months when wheel shelling is more pervasive and can contribute to (vertical split rim) failures," investigators wrote.
The train was headed from Falls, B.C., where the cars are loaded, to Prince Rupert on Dec. 21, 2011, when the wheel gave out and caused emergency braking.
No one was injured in the accident.
Peter Hickli, the regional senior investigator for the board, said there are inspection systems built into the rail system throughout North America called Wheel Impact Load Detectors, or WILD, which alert railways to potential defects by measuring the impact a wheel has on a rail as a train passes.
The American Association of Railways has set a threshold of 90,000 pounds of impact for rail operators to pull the train and replace wheels.
"Transport Canada has nothing with regard to wayside detection, specifically WILD detection, within their freight car inspection rules," Hickli said.
On Dec. 1, 2011, the safety board issued the safety advisory calling on Transport Canada to put such a threshold in place.
"The response we got from Transport Canada from that investigation was that they were going to convene a type of summit between the railways, Transport Canada, and possibly the (Federal Railroad Administration), as well," Hickli said.
"To my knowledge, that has not as yet happened."
No one from Transport Canada was immediately available to respond to the report.
Each railway does have its own protocols in place for wheel inspections, Hickli said, pointing out that CN has probably the most widespread system of wheel impact load detectors in North America.
"But there is no threshold in the regulations for mandatory replacement of defective wheels," Hickli said.
Hickli said the type of "vertical split rim" incidents that caused this crash have surfaced as the cause of several recent derailments.
Tiny cracks develop from wear on train wheels, and eventually cause pieces of the wheel tracks to fall away, he said.
"The rail industry is starting to see a few of these. It's a phenomenon that's fairly new," Hickli said. "Why that happens we don't know yet."
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