Do speed limiters always mean better mileage, less emissions?

There have been many compelling arguments made both for and against Ontario’s controversial legislation that, if passed, would mechanically limit truck speeds to 105 km/h. We’ve heard them all here at Truck News. Some of them have been absurd (that the Ontario government are communists and that truckers will take up arms before allowing their trucks to be governed). Others make a lot of sense – like this one:
Doug Monahan is one of those owner/operators who meticulously tracks his fuel mileage. He spec’d his latest truck with fuel economy in mind. It has a small, 450-hp Mercedes-Benz engine which allows him to average 7.73 mpg even without an aerodynamic tractor. He gets 8.7 mpg on flat ground and about 7.3 mpg through the hills.
Doug hauls into the US where he encounters a lot of these hills, especially through Virginia. While he averages 95 km/h here in Canada, he says he needs the extra juice to get over the hills without burning up too much fuel in the process. He generally approaches the bottom of the hill at 75 mph, which allows him to increase his fuel mileage by half a mile per gallon when all is tallied on the other side, he claims. He says he needs to keep the smaller engine wound up to maximize his fuel mileage in the hills. He has experimented by running his usual 95 km/h through the hills in the US and he says he saw his fuel economy suffer significantly.
“That’s money right out of my pocket,” he insists.
He claims that his smaller engine will put out more greenhouse gases if he’s limited to 105 even through the hills in the US. That’s because it will have to work so much harder to get up the hill if he can’t build up speed at the bottom. Now, Monahan is a reasonable guy and he knows that slowing down saves fuel. That’s why he spec’d a smaller engine. However, he said his fuel savings will lost if he has to run at 105 through the hills. And he’s not happy about it. He feels the proposed law should apply only to new trucks, since he would have spec’d his truck differently had he known about the proposed law at the time.
He makes a good point. When new regulations are hoisted upon the automotive industry, existing vehicles are usually grandfathered. He’d like to see the Ontario government follow that lead in this case as well.
“Then the owner/operators and the company know what they’re getting into and they can order the truck accordingly,” he points out.
George Desjardins, an owner/operator with 30 years experience, agrees that his fuel economy will suffer in the hills if his truck is governed at 105.
“In the perfect world these pro-speed limiters live in, there mustn’t be any hills,” he wrote to Truck News. “The world I live in there are, and when you are loaded with a gross weight of 130,000 lbs, you must drop gears to climb hills, even little ones. This causes the engine to rev up even though the truck is losing speed. If you can’t increase your speed a little prior to the hill, you will be in a lower gear and running with a higher RPM that much longer, thus spewing greenhouse gases into the air that much longer.”
He adds: “Being that at the present time I can speed up prior to climbing a hill, I can in a lot of cases stay in high gear and not contribute to this problem as much.”
Desjardins spent extra money on a big engine and now feels this legislation will, in his words, “castrate it.”
It’s not easy to determine to what extent fuel mileage may be compromised in hilly regions with the proposed law, if at all. But we mustn’t underestimate the implications the proposed speed limiter law will have on how fleets and owner/ops spec’ their equipment. Perhaps the law would be more readily received if current trucks were exempted from the rule?

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James Menzies is editor of Today's Trucking. He has been covering the Canadian trucking industry for more than 20 years and holds a CDL. Reach him at or follow him on Twitter at @JamesMenzies.

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  • I am confused by this issue. Apparently, slowing a truck to 105 kph. will reduce the severity of accidents on the highway, decrease the amount of greenhouse gases put into the atmosphere and reduce the amount of fuel used thus promoting conservation. I wonder what the result would be if small vehicles (cars and pickup trucks) were limited to a speed of 110 kph. At this slower speed; do you think that accidents involving these vehicles would be less severe? Would they not get better fuel economy and put less pollutants into the air? If you answered yes to these questions, why doesn’t the Government of Ontario mandate speed limiters on all vehicles in the province? Can anyone give me a valid reason why any vehicle in this country (other than an emergency vehicle) needs to go faster than 110 kph? If you were a parent of a new driver; wouldn’t you want your child in a speed limited car? Why would any car thief steal a car when he or she knew that any police car could easily catch them? What do you think would be the affect of a speed limited auto on your car insurance? Please do not even mention prohibitive costs. All cars today come equipped with engine management computers. The cost of modifying the program to incorporate a speed limiter would be minor. By comparison, the costs of installing seatbelts, crumple zones and air bags dwarf the cost of a computer program modification.
    Please don’t get me wrong; the company that I work for, governs all company trucks at 105 kph. That is not my problem. My problem is that I live in Canada. All citizens are governed by the same laws. To tell one group that they do not enjoy this equality is called DISCRIMINATION. We need look no further than to the Chinese labourers brought here to build our railways or the Japenese Canadians who were dispossesed during the Second World War or most recently to Aboriginal children who were forcibly removed from their families. In every case, these groups were subjected to different laws than the majority of Canadians. The Federal Government has admitted that this was wrong and that ALL Canadians should be treated equally. I would like to bring to the attention of Ontario that they already acknowledge this due to the fact that at present the maximum speed limit applies to all vehicles equally.
    I realise that my position may not sit well with most car drivers. However, does paying $100,000.00 for a Porsche entitle you to recklessly disregard the speed limit. No it does not. If you do not believe that the government has the right to tell you to put a speed limiter on your vehicle, then you cannot allow the government to impose speed limiters on one small group in our society. Tim LINSDELL

  • Speed limiters are not a good thing on any road. There are many sections of the 402 and 401 that are only 2 lanes in each direction. Do you think all the trucks are going to roll along at 105km/h in the right lane? All it takes is a heavy truck slowing on a hill and lighter trucks will move to the left lane to pass. Many of them will stay in the left lane when they realize traffic backing up behind them will block them in the right lane and prevent them from passing if the are behind another slow truck. If a truck can go 5 km/h over the speed limit they have every right to stay in the left lane to avoid ramp traffic and stay clear of emergency vehicles and disabled vehicles that may be on the shoulder. Drivers of lighter vehicles will just have to learn to be patient and observe the speed limit.