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News release

Associated links (R19C0002)

Failure of a rail car coupler led to 2019 rail yard collision and derailment in Calgary, Alberta

Calgary, Alberta, 9 July 2021 – In its investigation report (R19C0002) released today, the Transportation Safety Board of Canada (TSB) found that the failure of a railcar coupler knuckle led to an uncontrolled movement, followed by a collision and a derailment at the Canadian Pacific Railway (CP) Alyth Classification Yard in Calgary, Alberta in 2019.

On 06 January 2019, a crew was switching cars eastward into the Alyth Classification Yard in Calgary, Alberta.  At approximately 0655 local time, 56 cars disconnected from the yard assignment and ran uncontrolled down the lead track into the designated emergency track, contacting a cut of stationary loaded hopper cars. As a result of the collision, a total of 22 cars derailed. No injuries were reported. A small amount of fertilizer pellets was spilled and later recovered. The product was non-regulated and posed no threat to the environment.

The investigation found that the collision and derailment occurred when a knuckle on a car being switched failed while the cut of 75 cars was in motion. This led to the uncontrolled movement of 56 cars into the designated yard emergency track. The knuckle had developed fatigue cracking in the area of the knuckle pin bore and failed due to overstress. The age of the fatigue cracks and a post-occurrence examination suggest that manufacturing deficiencies weakened the knuckle, leading it to fail under normal service stresses. The fatigue crack was likely present during the last detailed inspection, two months prior to the occurrence, but was not identified.

The unplanned/uncontrolled movement of railway equipment is a Watchlist 2020 issue. Transport Canada (TC), the railway companies, and labour unions must collaborate, devise strategies, and implement physical and administrative defences to address each type of uncontrolled movement.

Following the occurrence, the TSB issued Rail Safety Advisory Letter 01/20 to TC and the Association of American Railroads regarding the defects found in the broken knuckle. CP made changes to its Alyth Classification Yard operation, including a fixed designated emergency track for all switching operations, increasing the number of cars that have air brakes, and limiting tonnage while switching. CP also added retarders to help prevent cars from exiting tracks in the Alyth Classification Yard and to slow the cars down during an emergency.

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
Media Relations
Telephone: 819-994-8053
Email: media@tsb.gc.ca