An undetected rail flaw led to a train derailment not far from Sussex, according to the Transportation Safety Board (TSB).
The federal agency has released its investigation report into the derailment near Dunsinane on Oct. 30, 2023.
A CN freight train with 46 cars was travelling along the line when there was a train-initiated emergency brake application.
The last four cars of the train had derailed and about 2,000 litres of methanol leaked from one of them. There was no fire and no one was hurt.
The investigation found the derailment happened when a section of rail broke as the train passed over a small bridge.
Officials said the break was the result of an internal fatigue defect that likely originated from fine cracks in the surface of the rail, known as head checking.
Inspection records revealed that the rail section had undergone third-party ultrasonic rail flaw detection testing using a hi-rail vehicle three times within the preceding five months.
None of those tests were able to obtain valid results and an ultrasonic hand tool did not identify any internal defects along the rail.
Investigators said the head checking on the rail’s surface likely affected the reliability of the ultrasonic testing in identifying the internal fatigue defect.
The TSB found if rail surface conditions that affect the reliability of testing do not have to be reported to a railway operator, internal rail defects can remain undetected, increasing the risk of a derailment.
