Better fuel economy starts with common sense
Speed bumps achieve traffic calming but are annoying for many reasons.
Apr 16, 2010
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Green Wheels
One of my pet peeves when driving (and how is it, anyway, that I’m the only one who’s perfect behind the wheel?) involves speed humps.
Not bumps, which are sharper and must be taken very slowly, but humps — those rounded little hills installed on residential streets.
They’re designed so cars can cross them comfortably at a speed limit of 30 km/h. But most drivers accelerate past 40 between the humps, and brake to ease over them at 10 or 15.
This isn’t just an annoyance. It’s also part of a pattern with environmental impacts.
One of the best ways to increase a car’s fuel economy — no matter its size and power — is to drive efficiently. Like so much related to the environment, it’s simple common sense. No sophisticated technology or new fuel is required. Batteries needn’t be included. And it’s absolutely free.
Smarter navigation of speed humps is just a tiny part of the picture.
The massive book of regulations and background information that accompanied new U.S. and Canadian fuel economy standards last week notes that published ratings for cars are generally much better than what’s achieved in the real world.
“Actual fuel economy levels achieved by light-duty vehicles in on-road driving fall somewhat short of their levels measured under the laboratory-like test conditions used … to establish compliance with the ... standards,” it states.
Real-world performance is roughly 20 per cent lower than published fuel economy levels, the book states. So, for example, if a car’s official measure is 10 L/100 km, the “on-road fuel economy actually achieved by a typical driver of that vehicle” is expected to be 12 L/100 km.
The gap is simply the difference between the fuel economy achieved under ideal conditions and what happens when human habits and mistakes mess things up. Some of the efficiency loss is usually considered to be beyond a driver’s control — rough roads, low temperatures, steep hills, traffic jams — although eco-driving purists suggest altering the timing and routing of trips to avoid them.
But we’re well able to do something about most of the difference. It has to do with keeping the car well tuned and the tires properly inflated; taking unnecessary heavy stuff out of the car; removing racks when they’re not required; and operating the gas and brake pedals with a lighter foot.
Speed has the easiest-to-measure connection to gas consumption. According to the U.S. Environmental Protection Agency (with my conversion into metric), this is what happens when you travel faster than 90 km/h:
• 96 km/h, fuel economy drops by three per cent.
• 105 km/h, drops by eight per cent.
• 112 km/h, drops by 17 per cent.
• 120 km/h, drops 23 per cent.
• 129 km/h, drops by 28 per cent.
Britain’s Green Road Technologies Inc. recently assessed impacts of the driving habits of 55 fleet drivers over several months, measuring more than 120 manoeuvres, such as lane changes, sudden braking, aggressive acceleration, and excessive speed.
It found that safer “green” drivers not only were in fewer accidents than those with “red” habits, but they also got from seven to 11 per cent better fuel economy; consuming, on average, two litres less gas per 100 kilometres.
Other tests conclude that air conditioning and other electronics increase fuel consumption by up to 25 per cent, and roof racks by 11 per cent.
As for speed humps, while the alternate braking and acceleration employed by most drivers is gas-guzzling, they’re such a small part of driving that approaching them properly would produce only a minute reduction in climate change. It would, though, be a big boost for my nerves.
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