August 2019 employee fatality at CN MacMillan Yard, Ontario, was caused by a string-line derailment
Richmond Hill, Ontario, 5 April 2022 — In its investigation report (R19T0147) released today, the Transportation Safety Board of Canada (TSB) identified a combination of factors that led to the death of a railway yard operating employee.
On 15 August 2019, at about 1:10 a.m., a Canadian National Railway (CN) remote control locomotive system (RCLS) yard assignment was pulling 82 cars northward along track W100 in CN’s MacMillan Yard in Vaughan, Ontario. The assignment was controlled remotely by a CN yard operating employee using a Beltpack, and who was operating the movement from the left side of the leading end of the 27th car. As the assignment negotiated a 15-degree left-hand curve, the trailing end of the 26th car behind the locomotives string-lined, causing it to derail along with the next eight cars. String-lining is the tendency of a long cut of cars to shortcut a curve when being pulled, a problem that is amplified in a heavier train when handling light cars that are followed by significantly heavier cars. All nine cars that derailed were empty multi-level autorack cars. During the derailment, the 27th to 29th cars overturned on their sides to the inside of the curve and pinned the employee under the 27th car. The employee sustained fatal injuries.
The investigation found that when the trailing end of the 26th car string-lined, the left side wheels of the trailing truck (wheel assembly) climbed the rail, derailing the car to the inside of a 15-degree curve. As it derailed, the 26th car pulled laterally on the leading-end coupler of the 27th car, causing the 27th car to roll off its trucks, separate from the head-end cars, and overturn on its side.
A series of train dynamic simulations were conducted in support of the investigation. The results identified that the RCLS programming caused an aggressive throttle response which in turn led to a rapid acceleration and run-out of train slack on the long tail-end heavy assignment. It was also determined that since a lighter cut of autorack cars equipped with hydraulic end-of-car cushioning devices was placed between two heavy cuts, the devices were compressed during the previous deceleration. Therefore, the aggressive acceleration of the assignment likely resulted in a rapid run-out of train slack, which contributed to the string-line derailment. Additionally, it was found that the air brakes likely remained on the 63rd car, which also contributed to the accident.
If railways do not reinforce safe, smooth train handling options for RCLS use during yard operations and provide more specific guidance for identifying conditions that are conducive to string-line events, the risk for a string-line event will remain.
Following the accident, Transport Canada completed an investigation under the Canada Labour Code, Part II.
CN has implemented several new processes systemwide, revised instructions for MacMillan Yard and re-configured track W100 in an effort to prevent similar accidents from occurring in the future.
See the investigation page for more information.
The TSB is an independent agency that investigates air, marine, pipeline, and rail transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.
For more information, contact:
Transportation Safety Board of Canada