NDP transport critic Olivia Chow says tougher regulations are needed for railway companies, following a CBC News report revealing that the number of runaway train incidents in Canada is nearly triple the number officially reported.

"It's shocking that Canadians have no idea there are all these runaway and uncontrolled trains that are across Canada," Chow told reporters. "These kinds of incidents should not be kept secret from the general public."

Transportation Safety Board annual reports from 2000 to 2012 have identified 158 runaway trains, counting an incident as a runaway only when it was the primary issue reported to safety inspectors.

But CBC News analyzed the complete TSB rail database of so-called incidents and accidents obtained through the Access to Information Act and discovered that runaways have been involved in more than 300 other cases. The majority of runaway train cases are categorized as derailments or collisions — without any indication that the train was rolling away uncontrolled at the time.

"We're seeing a decade of deregulations allowing companies to run the trains whichever way they want," Chow said. "So as a result you see runaway trains, unreported incidents, lack of penalties, no investigation. That's why tragedies happen and why we must do better. We must put Canadians' safety as our top priority."

Chow said someone needs to be holding rail companies to account with fines.

"There has to be penalties. If not, the practices of rail companies become sloppy, and accidents happen, tragedy happens."

Calgary Mayor Naheed Nenshi said he's been been fighting for months to learn more about dangerous goods being shipped by rail through his city.

He said he was surprised to learn there have been 29 runaway trains over the last decade in Calgary, most in yards, but some on main tracks, including six cases involving tankers loaded with dangerous goods.

"No question we have to close the information gap," Nenshi said. "First responders and cities need to know about all of these incidents."

Wayne Benedict, who spent 15 years working as a railroader before becoming a lawyer and rail commentator, said the TSB doesn't have the resources to probe all runaways. He added that Transport Canada has been slow to implement recommendations.

"If they investigated and reported on every single incident — if no one is following the recommendations, what's the point?"

In response to the CBC report, the TSB said it has "investigated every major runaway, derailment and collision with the potential to net significant safety lessons and we have reported on those publicly."

"For the remainder, the TSB has tracked all of them and has analyzed them to look for trends and emerging safety issues," John Cottreau, a TSB spokesman, said via email. 

"Whether it is one car or a whole train, if it runs away, it must be reported to the TSB. If only a few cars run away and stop, then it is classified in our database as a runaway," he said.

"If the chain of events begins with a runaway but results in something more serious, we call it what it is: a derailment or a collision and record the information about the runaway aspect in the occurrence summary. It is as simple as that."

But the Transportation Safety Board declined an interview to answer why out of 459 runaways it has only investigated nine cases, all of which involved a serious accident.

Although Transport Canada said it has acted against rail companies involved in runaways, it has not provided an example of what was done in any of the 459 incidents revealed in the TSB records.

Meanwhile, Jeff Watson, parliamentary secretary to the transport minister, insisted that regulators do crack down if they find violations.

With files from Dave Seglins