The Transportation Safety Board of Canada (TSB) said a rail manufactured nearly 60 years ago was one of several factors that caused a Canadian National Railway freight train to derail near Saskatoon in 2019.
Twenty-nine cars and a mid-train locomotive left the tracks as the CN train hauling grain derailed on Highway 11 at Wanuskewin Road on Jan. 22, 2019.
The locomotive had a diesel leak and was on fire when emergency crews arrived.
READ MORE: CN train derails north of Saskatoon
In a report released Thursday, the TSB said a number of factors led to the train derailment.
One was the replacement of a damaged section of track in the highway median with a rail manufactured in 1953, the TSB reported.
Investigators said while rail was ultrasonically inspected before being placed in the track, manufacturing processes at the time the rail was made resulted in it having a lower fracture toughness.
This lessened its resistance to the propagation of fractures. A bolt hole crack formed in the 1953 rail and quickly propagated, resulting in the broken rail, TSB said.
“Less than one month after the most recent rail flaw inspection, the fracture had grown from a size that was not detected during ultrasonic inspections to a size that was sufficiently large to lead to a rail failure,” said the report.
The TSB said its investigation revealed risks associated with using rail manufactured with lower fracture toughness to repair sections of track that experience frequent bending forces.
“In such a case, there is a risk that rail defects will develop and progress to failure faster than they can be detected by the rail flaw inspection regime,” the report said.
The report also said a rail head was missing at a joint between two pieces of rail, leaving a gap in the rail surface.
Investigators said the impact of the train’s wheels further damaged the rail until it failed.
“It had likely been broken and expelled under a previous train, before the arrival of (the) CN freight train,” the report said.
“As the… train travelled over the gap in the east rail caused by the missing rail head, wheel impacts further damaged the rail until it eventually failed.”
The rails at this location are also subject to bending forces as trains travelling through this section of track pass from a well-supported track on the highway to less stiff track in the median between the roadways, the TSB reported.
This caused the track cross-level and surface alignment to progressively deteriorate, which in turn increased the deflection of the rail and the eventual failure, the report said.
The TSB report noted that traffic has increased in recent years in that location, increasing from 7.7 million gross tons (MGT) in 2013 to 19.1 MGT in 2018.
This exceeds a regulatory threshold requiring more frequent inspections, and according to the TSB, inspections have not increased despite the rise in traffic.
The regulations stipulate that tracks with more than 15 MGT of yearly traffic must be inspected at least twice yearly.
The TSB said this did not occur at the Highway 11 crossing.
“Had the additional track inspections been undertaken as the TSR require, the track in the vicinity of the Highway 11 crossing could potentially have been identified as a location with significant track deterioration, requiring further track surface maintenance,” the TSB report said.
“Although the CN track information system recorded details of repairs made to the track, it did not provide sufficient resolution to assess the work conducted at individual joints where short pieces of rail were installed close together, as was the case in this occurrence.”
In a statement to Global News, CN said safety is a core value of the company and it learns from every incident.
“Inspection frequency has increased at the crossing,” the statement said.
“We would like to apologize to local citizens for the impact and inconvenience caused by this incident and thank local first responders for their assistance and support.”
The TSB added its investigation has concluded.