TSB determines broken wheel led to CN train derailment

The Transportation Safety Board of Canada (TSB) has determined a broken wheel, caused by a service-related failure, led to a CN train derailment in January 2016 near Webster, Ontario.

The accident occurred Jan. 9, 2016, as the train was moving west on the Redditt Subdivision and experienced a train-initiated emergency brake application near Webster. A total of 26 cars derailed, including six Class 111 residue tank cars that last contained diesel fuel.

There were no injuries and no product was released, according to a TSB press release.

In its investigation report released yesterday, the TSB found that a progressive fracture on a wheel of the second car from the head end eventually allowed the wheel to move inboard on the axle and derail.

The train continued to travel on the track about 8 more miles before the cars derailed, setting off the train-initiated emergency brake application.

About 14 minutes before the accident, the train passed a wayside inspection system (WIS) where a wheel impact load detector (WILD) recorded the impact load of the defective wheel. While the reading exceeded the Association of American Railroads (AAR) condemning limits, CN WILD guidelines permitted the wheel to remain in service without restriction until it reached its certified car inspection location.

The development and implementation of WILD technology has been an industry initiative to enhance rail safety by proactively identifying wheels with defects that can cause derailments or damage to track infrastructure.

However, if railway WILD guidelines do not provide adequate guidance for dealing with wheel impacts that are condemnable under AAR rules, there is an increased risk that wheels with emerging defects will not be identified and removed from service before progressing to failure, TSB officials said.

In response to a 2011 TSB rail safety advisory, Transport Canada (TC) indicated it would create a joint TC-industry forum to comprehensively review WIS and WILD criteria. However, TC has made no progress on guidelines, standards or rules for use of WILD technology, according to the TSB.

"In the absence of WILD condemning limits within the TC-approved Railway Freight Car Inspection and Safety Rules and/or other related TC guidance, WILD company guidelines may not be sufficiently robust to consistently protect against wheel failures," the TSB concluded.