A Transportation Safety Board report blames a combination of freezing and thawing weather conditions and the widening of some rail tracks for a train derailment near Fernie last year.
Twenty-seven cars of a 115-car Canadian Pacific coal train travelling westbound jumped the tracks in March 2011 when the wheel of one car dropped inside a track, pulling the other cars off the rail. There were no injuries.
The TSB report says the tracks in the area of the derailment had a wider gage, or gap, between them, after taking on many large heavy loads.
Investigators also found ice buildup at the base of the rail, which they decided was a result of freeze and thaw cycles, along with rain and snow around the time of the derailment.
The report concludes the wide gage of the rails was up to safety standards, but that current standards for upgrading railing fastening systems in high-degree curves may not be adequate.
New Transport Canada rules coming in later this month say that track-gage tests must be conducted at least twice a year on rails carrying more than 35 million gross tons.
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.
The report is available on the TSB website at www.bst-tsb.gc.ca.