Survey: Slow is the New Fast, Episode 2: Cars
by Lloyd Alter, Toronto on 10.11.07
We have previously asked whether speed limits should be lowered; Now we want to know, do you respect and follow the ones we have? Fuel consumption increases dramatically with the increased air resistance at higher speeds, but driving slowly has other benefits. You get to travel more interesting routes and learn more about your country; as we noted in an earlier post, perhaps we need a slow car movement.
i hate speeders - they are a danger to those who chose to NOT BREAK LAWS. . .
bet they don't use blinkers, either :(
given that most daily drives are relatively short
1) i submit that very often people who speed past me - i find myself catching up to them at traffic lights - so much for that extra energy it took to speed past me
2) i also submit that speeding around like that only gets you to your destination with a marginal time saving. For 30miles, 55mph=32minutes; at 75mph=24min. Some will argue and of course it depends on the situation but mostly i think that 8minutes just doesnt seem that valuable...
I'm fairly sure that the '55' movement is quite out of date. When the original idea was brought to the public, the average horsepower of a new car on the road was around 130 horses, and you were most likely using a 3-4 speed. Today, the number of new cars sold with over 200 horsepower is something close to 75%. Most of these cars have at least 5-speeds or even 6. Drag coefficients are also now much lower.
Taking all of that into account, the amount of savings, driving a new car, between 55 and 65 is negligible. *Maybe* one or two mpg. The costs in fuel mileage is mostly due to driver habits of accelerating at a high rate. Now for trucks, SUV's, and tractor trailers (and their high drag) this is a much different story. I say let cars go faster, and keep gas guzzlers in the slowlane.
Although I have to say, I get better than EPA mileage on my newer Toyota truck on the freeway at 65. 23 miles a gallon average is more than decent for a fullsize truck. Going slower at 55 doesn't seem to help much, as the RPM change with the 5-speed goes from 1900 at 65 to 1750 at 55.
why are all these "treehuggers" driving so fast? Altering your driving style is one of the easiest ways to improve mpg
I've found that by dropping from the posted 70 MPH to about 62 MPH and coasting on the long hills I've increased the MPG of my car by about 10%
Driving the speed limit or 5 under is best. You can be just as big a danger driving 55 in a 75, as a driver doing 85 in a 75.
I have a very accurate fuel consumption computer that I have tested at sea level in a 1998 Jeep Grand Cherokee 6 cylinder.
55 mph = 24 mpg
60 mph = 20 mpg
65 mph = 17.5 mpg
70 mph = 14 mpg
75 mph = 12 mpg
Downshifting to pass from 65 mph = 8 mpg.
The difference in engine speed varies little between 55 and 70, and is actually in a more efiicient range at the higher speed, but the increased wind resistance aboslutely murdered the efficiency.
I realize all of these (mpg) numbers are low, but I wanted to highlight the effect speed has on a mid-size SUV.
It's not the speed, it's the energy use.
Driving smoothly and consistently is the key to maximizing gas milage. Start slow, keep steady pressure on the accelerator, and try to anticipate traffic conditions to avoid braking.
Short congested commutes are a real gas hog as the car rarely has a chance to warm up to proper operating temperature, and all of the starts and stops mean heavy acceleration and no conservation of forward momentum.
My old, large car can get 30mpg at a steady state, level, 100mph. Best trip milage I've ever seen was about 34mpg, while average milage winds up being about 28mpg. With 4 people riding you do better than a bus.
Most cars do get their best milage at between 35 and 45 mph. But that is for a constant speed. Most commuting routes don't permit that, with frequent stops or higher average speeds.
On a short commute the minute or two saved by going faster won't make much difference. But when you have to drive a few hundred miles, then saving two hours starts to look a whole lot better.
Best of all, I can walk to work and use my car rarely. When the trip is a little longer I can often take public transit. It's good to have many tools so you can use the one best suited to each task.
"why are all these "treehuggers" driving so fast? Altering your driving style is one of the easiest ways to improve mpg"
So is not driving, and there are thousands of other ways to reduce your impact on the earth, and I'm sure no one does every single one of them. I find it a bit hyporitical when one questions someone's treehugger committment based on a single action. We are a sum of our parts and driving slow with your tires fully inflated in the smallest car you can drive to meet your needs is just one of many things an individual can do (albeit a big one!).
No one has mentioned drafting trucks . . . I had heard about people doing it before, but then when MythBusters found that you could get a 40% increase in mileage and still be 3 car lengths back (numbers are approx. based on memory) I gave it a try.
I drive a convertible and at 70 mph behind a truck the wind noise is comparable to 25 . . . cool stuff.
The very reason I got a Prius (2006).
50+ Mpg = 50 MPH
48 Mpg = 55 MPH
...and so on...
40 Mpg = 80 MPH
Plus, the Prius, like other Hybrids have super low PZEV ratings, so even at high speeds / demands, the pollution output is minimal.
Oh, for you doubters out there.
I can surpass posted limit, going uphill loaded with 4 adults with luggage. Still in the 40's MPG.
Bah, the only people that believe these numbers that I post are other Prius owners, scratching their heads, wondering why the Prius gets bad press at being slow.
This car still amazes me a year later.
The only negative thing I have to say about it is the all plastic interior that will rattle on you, especially at high speeds without the radio playing. Many of which have been fixed on the 2007 & the 2008 models.
For all the whiny slowpokes out there, have you considered that strolling along at or below the posted speed limit in the left lane causes rubbernecking behind you, which means people have to brake and slow down before having to accelerate to pass you? Did it occur to you that this activity actually wastes more fuel overall than the fuel you *think* you are saving by going slowly?
As usual, you just think about your own high and mighty selves.
Since the NHTSA can forcibly regulate the speed of Neighbourhood Electric Vehicles to 25 mph with computers onboard, we should use that same technology (computer chip on board ) and regulate the top speed of ALL freeway-speed vehicles to 55 mph.
If no one else is speeding, its easier not to drift into the habit yourself. As it is now, the rich can speed because they can afford the ticket. But we would all benefit if no one could speed.
I have a 2007 Toyota Prius. I drive on the freeway and in the city streets to work to average 52 MPG. I also have noticed that if i drive slower on the freeway I will get getter MPG, but the Prius can drive quite fast when needed.
Slower freeway speeds would be greater overall. On a second note, would anyone else want to see a solar panel option for future models of the Toyota Prius? I know I would.
Check out this website. The slower we travel in our cars the less pollution we will make.
www.70max.com
I think I read that air drag really starts making a difference above about 60mph
Check out this one-minute video about 'CO2scious' ECO-DRIVING, "Light on the Pedal, Light on the Planet":
http://truths.treehugger.com/video/contest_entry_light_on_the_ped.php or
http://next.video.msn.com/video.aspx?vid=f2556652-9ce7-44d6-8664-8ff2fca8d551
HOW we drive is as important as the choice of WHAT to drive (which has been getting all the attention) -- but car-purchasing decisions occur once a half-decade at best, while the choice of how to drive is made in every moment we are behind the wheel. Driving at, say, 55 mph instead of 65 mph on urban freeways will reduce fuel consumption, with all of its emissions and other externalities, by some 10 percent. Slowing to 50 while driving up sustained long hills will save even more. Accelerating gradually instead of forcefully on freeways, highways and surface streets also will reduce fuel consumption and emissions, as will gradually slowing in advance of red and yellow traffic lights ahead.
This is because fuel economy declines rapidly after 45 or 50 mph in the cars that continue to comprise the vast majority of the fleet. The average car uses some 17 percent more gas when you drive it at 65 mph than at 55 mph, and about 25 percent more gas at 70 mph. Another way to put it is, you can improve your gas mileage 15 to 20 percent by driving 55 mph rather than 65 mph. Some estimates suggest that fuel economy decreases by 2 percent for each 1 mph increase in speed over 55 mph; above 65 mph, the rate of decrease is even greater. The benefits of fuel-efficient driving will be the greatest in guzzlers.
I call it ECO-DRIVING: consciously-fuel-efficient driving that reduces gasoline consumption and its emissions. Eco-Driving also will help move the driving environment back toward the more moderate, more polite, and less-road rageful conditions of the past.
Driving this way will also spare some two- and four-legged pedestrians grievous injuries and death.
Automotive mileage improvements are typically seen as the province of automotive engineers and car manufacturers, policy makers, and auto purchasers. Rarely remarked upon is the ability -- and, I think, the duty -- of individual drivers to play the very considerable role they can to reduce global warming emissions, along with fossil energy dependence and energy insecurity, oil wars, road carnage, local air pollution, and growing trade imbalances.
Increasing the collective automotive mileage of the United States by just one mile per gallon would eliminate the need for drilling into the Arctic National Wildlife Refuge -- and increasing the U.S.'s collective mileage by some seven mpg would wean the U.S. off of Middle-Eastern oil, says Robert Kennedy, Jr. of the Natural Resources Defense Council. Eco-Driving -- if it becomes a trend and a commonly observed best practice -- will accomplish this saving and a lot more!
Anyone who claims to care about the environment -- or the country -- who drives a car can do one very simple thing almost every minute they are behind the wheel: slow down! Slower is greener, whatever car you are driving.
Gregory Wright greg@newciv.org