A probe into how 74 rail cars were allowed to roll uncontrolled for five kilometres onto a busy track just north of Toronto has resulted in investigators calling for Transport Canada to overhaul training requirements for some railway employees.

The Transportation Safety Board (TSB) initiated its review after a June 17, 2017, incident at CN Rail's MacMillan Yard in Vaughan, Ont.

It found gaps in the training process partially contributed to workers losing control of the 1,372-metre, 8,163 tonne train, which rolled at speeds of nearly 50 km/h until its momentum was halted by an upward slope. One tanker car was carrying a mixture of ethanol and gasoline.

"Ever since the disaster at Lac Megantic in 2013, Canadians need no reminders of the dangers posed by uncontrolled or runaway trains," said Faye Ackerman, a TSB board member.

"Moreover, in the last five years, the number of these uncontrolled movements has been on the rise."

Ackerman was among three experts who presented the TSB's findings at a morning news conference in Toronto. She said the probe determined that the two employees who were assembling and moving the 74-car train "lacked the knowledge or experience to properly control it."

Ackerman called on Transport Canada, the ministry responsible for Canada's rail network, to immediately update training standards for employees in "safety-critical positions."

"Transport Canada has been promising a regulatory update for years, as far back as 2003. Now is the time for action ... There can be no more delays," she said.

Technology outpacing regulations, TSB says

According to Rob Johnston, a regional manager of rail investigations at TSB, the crew on shift at the south end of MacMillan Yard, where the train was assembled, consisted of a foreman and a "helper." Both were "qualified conductors" with two years experience, respectively, and both had expertise in using a belt pack — a remote control device used for assembling trains that reduce the number of workers required for the job.

Belt packs are widely used in the industry, Johnston said.

But while the packs have been associated with runaway train incidents in the past, Ackerman said Wednesday that "the problem is not technology."

In his remarks to reporters, Johnston explained that, like most rail yards, MacMillan's topography is like a bowl, with the outer edges elevated to help prevent rail cars from escaping onto the main track.

On the day of the incident, there was confusion among the two workers and the yardmaster, who oversees all the operations. In short, the foreman and his helper didn't appreciate how much braking power would be necessary to stop the massive train from rolling away under its own momentum, despite two earlier briefings with the yardmaster.

​As the pair attempted to move the assembled train, more and more cars rolled onto the downward slope of the outer edge of the yard. Once about two-thirds of them rolled onto the main track, the workers could no longer keep the train in control.

The cars rolled out onto one of CN's busiest cross-country rail lines, known as the "York Subdivision."

Ackerman pointed out that under the current training guidelines, the person best suited to understand the challenges of such a move would be a locomotive engineer. However, the introduction of belt packs has eliminated their role in the process.

"Although the crew was aware of the [train's] significant size, they lacked the knowledge to fully understand how it influenced the way it handled," she said.

"That is, how the cut of cars would move, or stop and start based on characteristics such as length, tonnage, and weight distribution."

Under the current training requirements and regulations, however, the two workers were technically qualified to carry out the work.

"Those regulations do not cover the way that work is carried out today. That's because in the 31 years since those regulations were first issued, work has evolved," Ackerman said.

"So long as these gaps in regulations remain, Transport Canada won't be able to fix the problem ... That means the risk of uncontrolled movements and other accidents will continue."