On 10 January 2018, a Canadian National Railway Company (CN) freight train was proceeding southward on the Luscar Industrial Spur from a coal loading facility near Cadomin, Alberta. The train experienced a loss of control while proceeding down the mountain grade to Leyland, Alberta, reaching a maximum speed of 53 mph before coming to a stop at Mile 0.5. There were no injuries.
The investigation found that the uncontrolled movement occurred because the available air brake capacity was insufficient to control the train as it descended the steep mountain grade of the Luscar Industrial Spur. Inspection immediately after the train came to a stop revealed that the air brakes on 27 of the 58 loaded coal cars were not applied. While the train was at Luscar, the temperature dropped below a critical point, which adversely affected the function of the air brake control valves on the cars in this train. At the time of the occurrence, the ambient temperature was −24 °C.
Worn rubber seals in the air brake control valves installed on the rail cars shrank in the extreme cold temperatures. This type of failure was known to the industry and was the subject of an Association of American Railroads (AAR) circular in 2013. The failure repeated itself in this occurrence, resulting in auxiliary reservoir leakage and the unintended release of air brakes on 27 freight cars following brake applications. If performance issues involving rubber components in air brake control valves are not fully analyzed when they occur, degradation in the efficacy of the control valve, particularly during cold weather conditions, may not be identified and addressed in a timely manner, increasing the risk of a loss of control event.
Uncontrolled movements involving a loss of control are considered low frequency/high risk events. Between 2010 and 2019, loss of control events accounted for 4% of the 589 uncontrolled movements reported to the TSB. However, 57% of the loss of control events affected the main track, increasing the potential to encounter the public at crossings or collide with other trains. The TSB remains concerned that the current defences are not sufficient to reduce the total number of uncontrolled movements and improve safety.
Following the occurrence, CN implemented new air brake testing procedures for cold weather operations at Luscar. Loaded coal train operations at Luscar cease at temperatures below −25 °C, and are restricted to daytime operations between −22 °C and −25 °C. The railway implemented enhanced air brake control valve testing and replacement intervals for railcars owned by the company and leased railcars. The AAR introduced a change to its Field and Office Manuals of Interchange Rules requiring the renewal or replacement of brake control valves based on age and/or exposure to cold weather operations.
See the investigation page
