On July 6, 2013, an unattended 73-car freight train carrying crude oil rolled down a 1.2% grade and derailed in downtown Lac Mégantic killing 47 people in the subsequent explosion and fires. More than 30 buildings in the town's center, roughly half of the downtown area, were destroyed, and all but three of the thirty-nine remaining downtown buildings had to be demolished due to petroleum contamination of the townsite

The train began to roll downhill towards Lac-Megantic early on the morning of July 6 and after fire fighters had recently responded to a fire associated with one of the locomotives. With the locomotives shutdown and not providing a constant supply of air to the air brakes, air pressure bled off and the train began to roll unaccompanied and without power. Upon reaching the downtown of the city, the train is estimated to be at speeds of 105kmh when normal speeds in the yard and the curve that the derailment happened was 16 kmh. An insufficient number of handbrakes were set to prevent rolling in the absence supplied air.

Root Causes:

Safety Culture:

• “An organization with a strong safety culture is generally proactive when it comes to addressing safety issues. MMA was generally reactive. There were also significant gaps between the company's operating instructions and how work was done day to day. This and other signs in MMA's operations were indicative of a weak safety culture—one that contributed to the continuation of unsafe conditions and unsafe practices, and significantly compromised the company's ability to manage risk.” Transportation Safety Board

Management System Failures - System, Procedures and Administrative Controls Inadequacy

• An insufficient number of hand brakes were applied to prevent train movement in the absence of supplied air from the locomotive. The TSB estimates that between 17 and 26 handbrakes were required to be set; 7 were actually set.
• Single person crew operation of the train was seen to be a contributing factor as the train was left unattended at the time of the runaway.
• A repair on the locomotive eight months prior to the accident was insufficient and lacked durability. This “temporary” repair failed the night of the accident which resulted in the fire of the locomotive prior to the runaway.
• Additional findings included: not systematically testing petroleum crude oil, not planning and analyzing routes on which dangerous goods are carried, not having emergency response assistance plans in place, not ensuring that safety management systems work effectively