Canadian owner-op says speed limiters unsafe on downhill grades

By David Tanner, Land Line associate editor | 4/15/2010

The leader of a grassroots effort opposing mandatory speed limiters in Ontario, Canada, is concerned that the limiters could cause trucks to run away under certain conditions on downhill grades.

Owner-operator Scott Mooney, an OOIDA member from Cambridge, Ontario, says he has received testimonials from some drivers about the potential for a truck to gain speed on downhill grades inhibiting a trucker’s ability to slow the vehicle down.

Mooney said the situation could occur if a trucker experiences “brake fade” while on a downhill grade and while the limiter is set at or near the regular operating speed for the truck. Under those conditions, Mooney says the RPMs will fall, reducing the trucker’s ability to shift to lower gears or employ the engine brake.

“Once this happens, the truck will continue to accelerate out of speed control until it either reaches an incline, eventually slowing the truck, or by striking anything in the path of the truck, ending in a wreck,” Mooney stated in a press release and in a message to members of his Facebook group, Drivers Against Speed Limiter Legislation.

“This is to get the information out as a warning,” Mooney told Land Line. “To those that haven’t experienced it, look out. The other part of this effort is to inform the government about the danger. We have to let people know so they can change their methods. There are always people out there who won’t get it, but there are people who will.”

Tom Weakley, director of the OOIDA Foundation, says that yes, under specific circumstances outlined by Mooney, if a driver experiences brake fade on a downhill grade, the speed limiter could prevent the driver from being able to downshift.

“Technically, what he’s saying is correct,” Weakley said. “It could be a contributing cause to an unsafe situation.” Weakley says he has not heard of it happening, but that certain conditions could be such to cause it to happen.

Robert Clarke, former president of the Truck Manufacturers Association, cited similar concerns in an e-mail to Transport Canada back in 2007.

“When going downhill, driver braking will be required after fuel shutoff to control vehicle speed,” Clarke wrote at the time.

The Ontario Legislature passed a law in 2008 to require trucks heavier than 26,000 pounds to electronically limit maximum speeds at or below 105 kilometers per hour, or 65 mph. The law extends to all heavy trucks traveling provincial roadways including those from the U.S. and out of province. The highest posted speed limit on Ontario highways is 100 km/h, or 62 mph.

“If you’re traveling on a slope at the speed limit the province wants us all to travel – 100 km/h – it takes nothing to get up to 105. Then, this scenario could happen,” Mooney said.

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