Worker fatigue and a seized axle led to the November 2014 CN rail train derailment west of Terrace, an investigative report concluded last week.
Peter Hickli, Transportation Safety Board (TSB) senior regional investigator for rail/pipeline was designated the investigator-in-charge for the incident, which involved eight intermodal flat cars derailing near Kwinitsa, B.C., and carried 17 platforms.
The westbound train, which had emerged from a siding stop to allow another to pass by, travelled 12.5 km before conductors felt a ‘surge’ through the train after passing through a switch.
The CN workers halted the train after the emergency brake application had kicked in and “found that the No. 4 axle of the trailing locomotive was locked and had derailed.”
The No. 4 axle of the trailing locomotive locked when overheating parts on the traction motor assembly cooled down and seized together while the train was stopped in the siding.
“The locked axle prevented the wheels from rotating and caused the wheels to slide along the rail, become deformed, and then derail as the No. 4 axle passed through the switch near Kwinitsa,” the TSB report explained.
Coming out of the siding, workers noticed the train took longer to gather speed than normal. As well an alert for an intermittent wheel slip went off to mostly no concern due to its common occurrence when trains are pulling heavier cargo.
The crew also did not immediately notice an early announcement of an inspection of nine axles out of 424 (a damaged wheel set dislodged the heat sensors on the inspection system). Wayside inspection systems did not trigger alarms between the siding area and the derailment site.
Crew members were also operating with fatigue, partly due to erratic work schedules.
“In the preceding days, they had erratic sleep patterns due to work shifts with variable start and end times. Such work/sleep patterns cause circadian rhythm disruptions, which can decrease performance and cognitive function,” the report outlined.
“If shift start times are highly variable, train crew members may not be able to get good quality sleep on a regular basis, increasing the risk of accidents due to fatigue.”
The report stated that after the incident, CN reformatted its wayside inspection stations to include axle count as part of the post-scan announcement.
“CN has and is reviewing the report,” said Kate Fenske, CN Media Relations for Western Canada and Manitoba Community Affairs Lead last week.
In the Safety Management System 2015 Overview section of CN’s Leadership in Safety 2016 report, a ‘process with respect to scheduling’ was identified “to apply the principles of fatigue science when scheduling the work of the employees who work certain schedules” and “CN’s Fatigue Management Plan for train crews spells out the many initiatives that CN has in place to help address fatigue.”