News release

The Transportation Safety Board of Canada (TSB) released its investigation report (R21M0027) into the August 2021 freight train derailment that took place near Moncton, New Brunswick.

On 21 August 2021, a Canadian National Railway Company (CN) unit freight train transporting potash was travelling eastward on the Napadogan Subdivision when 30 hopper cars derailed near Pangburn Station, west of Moncton, New Brunswick. As a result of the derailment, 27 of the 30 cars were damaged, releasing most of their product. There were no dangerous goods involved, and no injuries were reported.

The investigation found that the derailment occurred when the track buckled under the train as it was decelerating on a descending grade near Pangburn Station. The track buckle likely occurred due to the combination of compressive thermal stress on the rail from the high ambient temperatures and exposure to direct sunlight, combined with the forces from the braking train and degraded rail anchoring. The neutral temperature of the rail (the temperature at which it is free of any tensile or compressive stress) had also decreased over its service life, creating instability at lower ambient temperatures and reducing the ability of the rail to resist buckling when subjected to compressive stress.

The railway company was carrying out work to reduce compressive thermal stress in the track and conducting visual inspections to detect built-up longitudinal stress. However, visual inspections can only detect physical signs of track degradation at a particular location or section of rail. They do not allow the advance identification of harmful levels of residual compressive stress in undisturbed rail or track structure. Consequently, tracks with rails under excessive compressive stress could remain undetected. In this occurrence, a hot weather inspection carried out on the day before the occurrence did not identify any sign of rail instability or track susceptibility to buckling due to excessive compressive thermal stress.

Following the occurrence, CN issued an operating bulletin instructing train crews to avoid excessive braking and limit the use of dynamic brakes from Mile 17.0 to Mile 21.2 of the Napadogan Subdivision.

See the investigation page for more information.