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Rail transportation safety investigation R19T0107

The TSB has completed this investigation. The report was published on 18 December 2023.

Table of contents

Main-track train derailment

Canadian National Railway Company
Freight train M38331-27
Mile 60.55, Strathroy Subdivision
Sarnia, Ontario

View final report

The occurrence

On 28 June 2019, Canadian National Railway Company (CN) freight train M38331-27 was proceeding through the CN Paul M. Tellier Tunnel en route to Port Huron, Michigan, in the United States (U.S.) when a train-initiated emergency brake applicationFootnote 1 occurred. A total of 46 rolling stock derailed in the tunnel, including a dangerous goods tank car that was breached during the derailment and released an estimated 12 000 U.S. gallons of sulphuric acid (UN1830, Class 8, Packing Group II). There were no injuries.

The accident

The westbound train had departed from Sarnia, Ontario, Canada (Mile 57.2 on the CN Strathroy Subdivision) on 28 June 2019, at about 0402 Eastern Daylight Time. The train was composed of 2 head-end locomotives and 1 mid-train distributed power remote locomotive, hauling a total of 140 freight cars. It was 9541 feet long and weighed 15 674 tons.

A train-initiated emergency brake application occurred at about 0420, while the train was travelling at 44 mph in the tunnel. The separated head-end portion of the train stopped outside the tunnel at Mile 61.46, while the tail-end portion stopped outside the tunnel’s east portal in Sarnia. A total of 45 freight cars and the distributed power remote locomotive had derailed and came to rest on both sides of the international border inside the tunnel.

The investigation determined that the accident occurred when bathtub gondola car DJJX 30478, loaded with scrap steel, sustained a structural failure and the A-end left side of the car collapsed, causing the car to derail in the tunnel on the Canadian side of the border. As car DJJX 30478 collapsed, the A-end truck became skewed beneath the car, causing both rails to roll outward and derail the trailing cars.

Structural defects that were present in the shear plates, stub sills, car body bolsters, and side sills, as well as thinned out steel sections due to corrosion of car DJJX 30478, negatively affected the ability of the car to withstand in-train forces. Bathtub gondola car DJJX 30478, built by Berwick Forge & Fabricating Corporation (Berwick Forge) in 1978, was used in a demanding service (i.e. scrap steel) for which the car was not originally designed, and there was no industry or regulatory requirement to periodically conduct a full inspection of the car to ensure it maintained its structural integrity. As a result, its structural integrity deteriorated and this was not identified prior to the accident.

As part of the investigation, analysis was conducted using train dynamics simulations and finite element modelling (FEM). The train dynamics simulations determined that in-train buff (compressive) forces of up to approximately 388 kips (388 000 pounds of force) were exerted on car DJJX 30478 while the car was in the tunnel. FEM failure analysis confirmed that, given the presence of the defects that compromised the structural integrity of car, the in-train buff forces exerted on the car resulted in the A-end structural failure that led to the derailment sequence. The maximum calculated buff force exerted on the car at the time of collapse represented a 61% reduction in the original design strength of the car due to its deteriorated condition.

Regulatory requirements for freight car inspection and safety

Rolling stock is routinely transferred at line points from one railway to another, a process referred to as interchange. Interchange occurs when a railway accepts a freight car for service on its line from another railway at line points or when crossing the Canada/U.S. border.

The Transport Canada (TC)-approved Railway Freight Car Inspection and Safety Rules (2014) (freight car safety rules) and the U.S. Federal Railroad Administration Code of Federal Regulations, Title 49, Volume 4, Part 215—Railroad Freight Car Safety Standards (2011) (freight car safety standards) establish the minimum safety criteria that apply to freight cars operated by federally regulated railway companies in each respective country. Freight cars that travel within Canada or the U.S. must comply with these minimum criteria, though both have provisions that permit freight cars with defects to be moved to a location for repair.

However, neither the Canadian freight car safety rules nor the U.S. freight car safety standards contain limits for damage to significant freight car structure, such as buckled side posts; ruptured side sheets, end sheets, and tub sections; negative side sill camber; buckled top chords; or extensive cracking and corrosion. Thus, the structural defects did not prohibit car DJJX 30478 from being interchanged.

Interchange of bathtub gondola car DJJX 30478

The bathtub gondola car that failed in the tunnel was in utility coal service for about 34 years. The Association of American Railroads (AAR) had qualified the car for “extended service,” which applies to freight cars built new since 01 July 1974. Being qualified for extended service permits the car to operate for up to 50 years from the original manufacturing date without the need to re-qualify the car, unless otherwise noted.

In 2012, the car was retired from coal service and purchased by the David J. Joseph Company Rail Equipment Group (DJJ Co.), as part of a larger purchase of 1650 similar cars, with the intention of using them in scrap steel service. DJJ Co. modified all 1650 cars by replacing the 4 reinforcement crossbars that obstructed top loading of scrap steel with 2 large steel u-channels fabricated inside the car to compensate for the structural change to reinforce the tub. The modifications for all 1650 cars were approved by the AAR.

At the time of its failure in the tunnel, bathtub gondola car DJJX 30478 was in a deteriorated condition and had a number of pre-existing defects that contributed to its reduced structural integrity. Visual examination of the car following the accident determined that the defects were not recent and would have developed over a period of time prior to the accident.

Despite its deteriorated condition, car DJJX 30478 travelled frequently within, and between, Canada and the U.S. and was interchanged between railways 16 times in the 6 months preceding the accident.

In the 3 months preceding the accident, car DJJX 30478 received 24 certified car inspections conducted at various CN line points, had numerous pull-by inspections, and traversed multiple wayside inspection systems, with no significant defects noted. In the year prior to the accident, the car only was only subject to routine maintenance.

National Research Council Canada compressive end-load testing of DJJX bathtub gondola cars

The Transportation Safety Board of Canada (TSB) contracted the National Research Council Canada to perform compressive end-load testing of 3 similar bathtub gondola cars to car DJJX 30478 that were present in the head-end portion of the train. The testing assessed the ability of these cars to withstand 3 consecutive applications of 1000 kips of longitudinal compressive force in their current worn state after 40 years of service. The tests were performed in accordance with the AAR Manual of Standards and Recommended Practices criteria for the design and construction of new freight cars.

Two of the tested cars that had been built by ACF Industries Inc. had thicker underframe steel members and each survived 3 consecutive applications of 1000 kips. The third car, a Berwick Forge car (DJJX 30156), which was the same design and vintage as car DJJX 30478, experienced structural failure at about 628 kips under testing during the first force application. As a result, the test could not be repeated.

Safety action taken

Transportation Safety Board of Canada

Following this accident, the TSB communicated critical safety informationFootnote 2 on

Transport Canada

In response to TSB RSA 08/19, TC wrote to the Railway Association of Canada and the Western Canadian Short Line Railway Association recommending that Canadian railways ensure that their equipment, procedures, and instructions be reviewed and updated, as required, to ensure employee safety.

In response to TSB RSAs 09/19 and 07/20, TC contacted the AAR regarding the issues mentioned in the 2 RSAs and continued to follow up with the AAR to ensure that all of the cars identified in the AAR-issued Maintenance Advisory MA-0188 were inspected.

Canadian National Railway Company

Following the derailment, CN inspected 416 of the 2130 identified cars of similar type and vintage to the occurrence bathtub gondola car and that were being used in scrap iron and steel service in North America. CN identified defects in 149 of the 416 cars (36%).

In response to TSB RSA 08/19, CN issued the Rule 83(c) Summary Bulletin Nov 2020 – April 2021, which included new tunnel emergency procedures that must be followed in the event of an emergency in the tunnel.

Association of American Railroads

The AAR issued maintenance advisories MA-0188 and MA-0198, Early Warning EW-5344 and Equipment Instruction El-0017 to the rail industry requiring the inspection of specified bathtub gondola cars. Equipment Instruction El‑0017, which was issued subsequent to the maintenance advisories and early warning, requires Berwick Forge bathtub gondola cars of the same vintage as the occurrence car to be inspected every 2 years. Cars identified in the equipment instruction are automatically prohibited from interchange under the AAR Interchange Rules unless they have been inspected within the 2-year timeframe and determined to be free from specified defects. The process will repeat every 2 years for each car on the list.

The 2020 AAR Interchange Rules governing centre sills, draft sills, coupler carriers, and side sills were revised to include causes for attention related to stub sills and side sills defects.

Media materials

News releases


Freight car structural failure led to 2019 train derailment in tunnel between Canada and the United States
Read the news release


Investigation Update Notice: June 2019 train derailment in Sarnia, Ontario
Read the news release


The Transportation Safety Board of Canada to conduct the investigation into the train derailment in the St. Clair Tunnel between Sarnia, Ontario, and Port Huron, Michigan
Read the news release


The TSB and NTSB are assessing CN train derailment in the St. Clair Tunnel between Sarnia, Ontario, and Port Huron, Michigan
Read the news release

Deployment notice


TSB deploys a team of investigators to the site of a train derailment in Sarnia, Ontario

The Transportation Safety Board of Canada (TSB) is deploying a team of investigators to the site of a Canadian National Railway train derailment in the Sarnia tunnel in Sarnia, Ontario. The TSB will gather information and assess the occurrence.

Investigation information

Map showing the location of the occurrence


Photo of Rob Johnston

Mr. Rob Johnston has been with the Transportation Safety Board of Canada (TSB) since 2001. He was Senior Regional Investigator in Winnipeg until 2004, when he assumed the position of Senior Investigator, Standards and Training Officer at TSB Head Office in Gatineau, Quebec. He became Manager of Central Regional Operations in November 2009, and served as Acting Director of Investigations - Rail/Pipeline for 9 months in 2010– 2011.

He now manages a staff of 6 rail/pipeline investigators in Winnipeg, Toronto, and Ottawa, and is responsible for all activities related to rail investigations in TSB’s Central Region, which extends from Cornwall, Ontario, to near the Alberta–Saskatchewan border.

During his time at the TSB, Mr. Johnston has been involved in over 100 TSB accident investigations including 14 major investigations as either an Investigator-in-Charge or as an investigation team member providing technical expertise.

Before joining the TSB, Mr. Johnston worked for Canadian Pacific Railway in Winnipeg from 1984 until 2001, where, as a member of the Train Accident Prevention group, he acquired an extensive background in mechanical operations, failure analysis, and dangerous goods.


Class of investigation

This is a class 2 investigation. These investigations are complex and involve several safety issues requiring in-depth analysis. Class 2 investigations, which frequently result in recommendations, are generally completed within 600 days. For more information, see the Policy on Occurrence Classification.

TSB 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 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.