Canada's TSB: CN derailment caused by poor wheel set performance

A wheel set issue was behind the derailment of a CN train near Brockville, Ontario, in July 2014, the Transportation Safety Board (TSB) announced in its investigation report yesterday.

The 26 derailed cars included 13 Class 111 tank cars containing aviation fuel residue. A small amount of product was released, and no injuries were reported, the TSB said in a press release.

The agency's investigation determined the train derailed because of excessive "truck hunting" — or side-to-side movement of wheel sets — on an empty 80-foot centerbeam bulkhead flat car. This type of car is less rigid that other types of cars. Under certain conditions, the side-to-side movement can become excessive, causing wheel lift or wheel climb, either of which can cause a derailment, TSB officials said.

In this case, the excessive truck hunting was influenced by car type, train speed (60 mph), the worn condition of the constant contact side bearings (CCSB), as well as by the truck type, TSB officials said.

Although little product was released in this derailment, the damage to the Class 111 tank cars was consistent with damage to Class 111 tank cars in other TSB investigations, officials said.

"The potential for catastrophic environmental impacts and loss of life remains, thereby reinforcing the need for improved tank car design standards," the press release stated.