Broken connector on a heavily loaded ore train caused a November 2024 derailment in eastern Quebec
A broken connector on a heavily loaded ore train caused a November 2024 derailment in eastern Quebec, the Transportation Safety Board of Canada (TSB) has found, highlighting risks from hidden defects in critical rail equipment.
On November 3, 2024, a southbound Quebec North Shore and Labrador Railway ore train derailed on the Wacouna Subdivision near Saumon Station, Que. According to the TSB, “7 cars loaded with iron ore on train BAL-481-F derailed on the main track at Mile 25.4 of the Wacouna Subdivision near Saumon, Quebec.”
Seven ore cars off the tracks, but no injuries
The unit train was hauling 240 cars of iron ore and weighed about 29,300 tons. As it moved at roughly 35 km/h, the brakes suddenly went into emergency mode and the locomotive engineer felt a hard jolt before the train stopped.
When the scene was inspected, the first seven cars behind the locomotives had left the track and about 250 feet of rail was damaged. The TSB notes “there were no injuries, and there was no environmental damage.”
Connector failure split the train in two
Investigators traced the problem to the coupler assembly at the back end of the second car. This hardware links one car to the next and absorbs the push‑and‑pull forces of the train.
During the trip, a key part inside the coupler system – the yoke – broke. That allowed the vertical pin that holds the drawbar in place to slide forward past its support plate and drop onto the track. As the TSB explains, “the drawbar at the B-end of the 2nd car became dislodged after the yoke broke, causing the yoke pin to move beyond the carrier plate.” With nothing holding it, the drawbar slipped out and the train came apart.
“The train separated after the drawbar had dislodged from the 2nd car,” the TSB found. When the two sections rolled back together, they hit at an angle, forcing the east rail to tip over and causing the derailment of the first seven cars.
Train‑handling was not an issue. Simulations showed the coupler had only seen normal forces for a loaded ore train. “The in-train forces before the yoke broke remained within Association of American Railroads specifications,” says the TSB.
Hidden casting defect and testing gap raise concerns
The failed yoke was a new part, installed about four weeks before the accident. In lab tests, the TSB found “the yoke had internal porosity in a high-stress area.” This small internal void, created when the steel was cast, was not visible on the surface but weakened the metal and allowed it to break under normal load.
The comparison yoke from the same manufacturer met industry requirements, suggesting this failure was rare. The report notes that “yokes are robust components whose design dates back several decades, with thousands in use throughout North America.”
However, the investigation points to a gap in current standards. Inspection of these parts after manufacture is mainly visual. The TSB stresses that “couplers are not required by the Association of American Railroads to undergo non-destructive testing,” such as ultrasound or X‑ray, which could reveal internal flaws.
For rail employers, the case is a reminder that even proven designs can fail when hidden defects slip through quality control, and that reviewing inspection and procurement practices for critical components can be an important part of managing occupational safety risk.
