Canadian and US transportation safety agencies Thursday called for stricter rules for moving oil by rail, following an eight-month probe of a Quebec derailment that left 47 people dead.

Large swathes of the picturesque town of Lac-Megantic, Quebec, were reduced to rubble after a runaway freight train carrying crude oil crashed and derailed in July last year.

"In the course of our Lac-Megantic investigation, we found three critical weaknesses in the North American rail system which must be urgently addressed," said Wendy Tadros, chair of Canada's Transportation Safety Board (TSB).

"Today we are making three recommendations -- calling for tougher standards for Class 111 tank cars; route planning and analysis; and emergency response assistance plans."

The statement was jointly issued by the US National Transportation Safety Board (NTSB).

Their recommendations on tanker cars have been sent to Transport Canada and the US Pipeline and Hazardous Materials Safety Administration, for consideration.

The structural integrity of so-called DOT 111 tank cars involved in the Lac-Megantic tragedy came under scrutiny following the accident, after it emerged the US Department of Transportation had identified safety flaws in the early 1990s.

A large number remain in service throughout the continent.

Tadros acknowledged that tanker car upgrades are already underway, and tougher standards are now in place for new models.

But she added, "a long and gradual phaseout of older model cars simply isn't good enough.

"It leaves too much risk in the system," she told a nationally televised press conference.

The TSB also urged Canadian railways to identify and choose routes "with the least risk" when transporting dangerous goods.

This means "changing how the trains are operated and lines are maintained, asking questions like how much product is being shipped? Are the tracks appropriate? Can populated areas be avoided? And are there environmental sensitivities?" Tadros said.

Finally, the TSB urged better emergency response planning in Canada.

According to rail industry figures cited by the TSB and NTSB, the number of carloads of crude oil shipped by rail in Canada has increased from 500 in 2009 to 160,000 last year.

In the United States, the number rose from 10,800 to 400,000 during the same period.