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Rail transportation safety investigation R21H0099

Table of contents

Train derailment

Ottawa Light Rail Transit (OLRT) train
90 m east of Tunney’s Pasture Station in Ottawa, Ontario

The occurrence

On at about 2034, an eastbound Ottawa Light Rail Transit (OLRT) train was proceeding from the north track to the south track at a speed of about 30 km/h, when it derailed about 90 m east of Tunney’s Pasture Station in Ottawa, Ontario. There were no passengers on board at the time of the derailment as the train was being moved from Tunney’s Pasture Station to OLRT Belfast Yard Maintenance and Storage Facility for repairs. The TSB deployed a team of investigators.


Site examination identified that, while negotiating the crossover, a wheel (no 3) climbed the rail and derailed to the field side of the south track. The mate wheel on the same axle derailed to the gauge side of the north rail and came to rest between the rails. The concrete ties and the tie plates of the south track sustained impact damage.

Roller bearing rollers were found on the track near the uOttawa Station. This suggests that, as the train travelled westward in the afternoon that day, a cartridge roller bearing assembly had failed and some rollers were expelled.

Event recorder and vehicle logs showed that the splined axle on the No. 3 wheel likely failed around 1325 as the light rail vehicle (LRV) travelled eastward between Cyrville and Blair stations. The LRV experienced multiple wheel slip warnings during this time. A root cause failure analysis performed by the manufacturer Alstom suggested that the roller bearing failure was related to the loosening of the large locking nut that holds the cartridge assembly together.

Roller bearing heat detection

Cartridge assemblies for OLRT LRVs are located inboard of the wheels and cannot be effectively inspected visually, and roller bearing operating temperatures cannot be monitored by traditional freight car wayside hot bearing detectors. Furthermore, OLRT has no wayside or on-board system in place to monitor the operating temperature of axle roller bearings that are located inboard of the wheels. Consequently, an overheated roller bearing within the cartridge assembly can potentially fail catastrophically without being observed or detected. As demonstrated in the present occurrence, this can also lead to derailment if there is no intervention.

Following the incident, it was decided that the entire OLRT LRV fleet required further inspection for loose cartridge assemblies prior to resuming operations. A series of risk mitigation measures were also put into place.

Safety communications


Rail Safety Advisory: Roller bearing failure resulting in derailment of Ottawa Light Rail Transit vehicle

Media materials

Deployment notice


TSB deploys team of investigators to Ottawa, Ontario following occurrence involving a light-rail train (O-Train)

Gatineau, Quebec, 9 August 2021 — The Transportation Safety Board of Canada (TSB) has deployed a team of investigators to OC Transpo Tunney’s Pasture station in Ottawa following the report of an occurrence involving an O-Train. The TSB will gather information and assess the occurrence

Investigation information

Map showing the location of the occurrence


Photo of Glen Pilon

Glen Pilon has been with the TSB since 2008 as Technical Coordinator and investigator at the TSB Head Office in Gatineau, Quebec. He has been the investigator-in-charge of a number of rail accident investigations and has acted as train operations expert on many others. Mr. Pilon worked for the Ottawa Valley Railway (OVR) from 1996 until 2008 as locomotive engineer and safety officer and with the Canadian Pacific Railway (CP) from 1987 until 1996 in operations as trainman and conductor.

Class of investigation

This is a class 5 investigation. Class 5 investigations are limited to collecting data, which are then stored in the modal database. If TSB investigators deployed to the occurrence site, a short description of the occurrence is posted to the TSB website once the investigation has been completed. These investigations are generally completed within 90 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.