Ottawa and the provinces will begin a study this fall to determine whether slowing down big trucks will hurt Canada's competitive position with the United States.
It's part of an effort to see whether it makes sense to limit transports to 105 kilometres an hour using microchip "speed limiters."
"There are some unknowns that need to be [addressed] before a decision is considered," said Brian Orrbine, head of the motor carriers division of Transport Canada. Those unknowns include whether U.S. truckers might avoid Canadian highways because of the limits.
The proposal originated with the Canadian Trucking Alliance, which represents the major transport companies, as a way to make driving safer while cutting down on emissions and fuel consumption.
The alliance says the average tractor-trailer could save $8,000 in fuel a year by travelling at the lower speed. The group also says slower trucks have more chances to avoid accidents.
A report could be ready this spring.
However, Ontario promised in July to limit truck speeds, and a Quebec legislative committee has backed the idea.
While safety is an issue, the federal government mentioned cutting greenhouse gas emissions in its 2006 description of the effort to assess speed limiters for trucks.
The Canada Safety Council, the Lung Association and others quickly backed the plan.
But other industry groups say the limiters will make it hard for truckers to merge, pass or keep up with other vehicles, especially in provinces and states where speed limits are higher.
Barry Prentice, head of the University of Manitoba's transport institute, warned that limiting truck speeds could cause more accidents as other drivers try to overtake the slower vehicles.
"We'll have all these other yahoos trying to pass trucks left, right and centre, especially on two-lane roads," Prentice said.
With files from the Canadian Press