Railway Investigation R15T0173

Runaway rolling stock, collision and derailment at CN MacMillan Yard, Vaughan, Ontario

The occurrence

At approximately 1330 on 29 July 2015, a Canadian National (CN) remote control yard assignment was pulling 91 cars (weight - 8972 tons, length - 6112 feet) up the hump lead track at CN’s MacMillan Yard. Near the top of the hump, the cars detached from the locomotives and the movement began to roll uncontrolled southward, down the grade and into the north end of track R-13 just as CN train A42241-29 (CN 422) was pulling northward into the track from the south end. The CN 422 crew was warned of the approaching uncontrolled movement and subsequently brought CN 422 (weight – 10171 tons, length – 11385 feet) to a controlled stop before evacuating to an area nearby.

The uncontrolled movement, led by 24 Class 111 tank cars loaded with petroleum crude oil (UN1267), reached a speed of more than 9 mph before colliding head-on with the lead locomotive of CN 422. The lead locomotive was shoved backwards about 400 feet which resulted in the derailment of 9 cars near the head-end of CN 422 and damaged 3 other cars on the adjacent track. There were no injuries and no dangerous goods leaked.

Map of the area


Photo of Don Mustard

Don Mustard is a Senior Investigator with Rail and Pipeline Investigations at the Transportation Safety Board of Canada (TSB). For the last 13 years he has been an Investigator-In-Charge (IIC), Standards and Performance Specialist, and team member on numerous completed rail and pipeline accident investigations, including Lac Mégantic. Previously, he spent 13 years providing geological and communication services to resource companies and Canada’s nuclear regulator.

Mr. Mustard holds a B.Sc. in Geology from the University of British Columbia, and a B.A.A. in Radio & Television Arts from Ryerson Polytechnic Univesity. In 2014, he received an Excellence in Investigation Award for his contributions in the investigation of the VIA Rail train derailment at Burlington and a Public Service Award of Excellence for his contributions to the Lac Mégantic investigation. His research work has been presented and published at international industry events such as the International Heavy Haul Association and the International Level Crossing Safety and Trespasser Prevention Symposium.


See more high resolution pictures on the TSB Flickr page.

Transportation Safety Board investigation process

There are 3 phases to a TSB investigation:

  1. Field phase: a team of investigators examines the occurrence site and wreckage, interviews witnesses and collects pertinent information.
  2. Examination and analysis phase: the TSB reviews pertinent records, tests components of the wreckage in the lab, determines the sequence of events and identifies safety deficiencies. When safety deficiencies are suspected or confirmed, the TSB advises the appropriate authority without waiting until publication of the final report.
  3. Report phase: a confidential draft report is approved by the Board and sent to persons and corporations who are directly concerned by the report. They then have the opportunity to dispute or correct information they believe to be incorrect. The Board considers all representations before approving the final report, which is subsequently released to the public.

For more information, see our Investigation process page.

The TSB is an independent agency that investigates marine, pipeline, railway and aviation 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.


Deployment notices


TSB deploys team to MacMillan Yard in Toronto, Ontario, to assess runaway train
Read the deployment notice