Lack of risk assessment among factors leading to 2016 CN derailment near Grey, Alberta

EDMONTON, March 22, 2018 /CNW/ - Citing a combination of factors, including use of dynamic brake, train speed on a curve with insufficient superelevation, and the lack of a formal risk assessment, the Transportation Safety Board of Canada (TSB) today released its investigation report (R16E0102) into the 2016 Canadian National Railway Company (CN) derailment north of Grey, Alberta.

In the early evening of 29 October 2016, a northbound CN freight train, travelling at 27 mph and negotiating a 6° right-hand curve on a descending grade, derailed 28 covered hopper cars loaded with frac sand at Mile 96.38 of the Grande Cache Subdivision. About 1300 feet of track was damaged. There were no injuries.

The investigation found that, in September 2016, the worn low rail in the curve had been replaced with a new, full-height rail, which reduced the height difference between the low and high rails (i.e., the superelevation) in the curve. When the low rail was replaced, its securement was strengthened. The fasteners of this replacement full-height rail were stronger than those of the high rail, creating uneven resistance to gauge-widening forces between the two rails. This uneven resistance left the high rail more prone to rollover.

The Grande Cache Subdivision is a secondary mainline with longer, steeper grades and was not built or maintained to standards for primary mainlines. In 2014, northbound distributed power unit trains loaded with frac sand began operation on this subdivision. During train operation, when the automatic (train) brake is used, braking effort is initiated on all cars. In comparison, when dynamic braking (DB) is used, braking effort is concentrated at the locomotives. Company procedures indicated that DB must be used as the first means of initiating a speed reduction. The derailment occurred when the high rail rolled over due to a combination of factors, including lateral forces on the high rail at the lead locomotives due to the use of dynamic brake, and train speed on the curve with insufficient superelevation.

The investigation determined that no formal risk assessment had been conducted before the operation of the short covered hoppers in unit train service began. If risk assessments are not conducted for changes to train operations, including locomotive type and traffic type, potential hazards associated with the operational change may not be identified and appropriately mitigated, increasing the risk of accidents such as this occurrence. Safety management and oversight is a Watchlist 2016 issue. As this occurrence demonstrates, potential hazards involving operational changes must be identified and assessed to ensure that appropriate mitigation strategies are developed and implemented.

See the investigation page for more information.

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.

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SOURCE Transportation Safety Board of Canada