Do you want to save gas? Stick to the speed limit!
Keeping your car moving under the speed limit is one of the tips that commonly appears when people talk about saving fuel. It's probably one of the tips most people respect the least, though, which can bring joy to some traffic authorities can then "remind" motorists - via a ticket and a fine - to drive slower. A website created to promote slower driving has even published a complete report on how much time you really save when you drive above the limit. Surprise: it's not much. For instance, for a 20-mile commute, at a sustained speed of 70 mpg (15 MPH over a 55 mph speed limit), you only save around five minutes. If five minutes is the trade-off at the expense of higher carbon emissions, maybe it's time to re-think what that time is worth. Thanks to Ryan for the tip!
[Source: Drive the speed limit]
Reader Comments (Page 1 of 1)
mike 4:40PM (12/25/2008)
55 mph is an artificial limit. Most roads were designed for safe 70+ mph driving. We should design cars to be most efficient at those speeds.
5 minutes every 25 miles adds up if you travel long distances. On a 300 mile trip you would save an hour of travel time. It works for me here in the mid-west.
55 mph was a way to tax people without taxing them. Remember all the speed traps in smaller communities? The police should be fighting real crime.
The safety credibility of a speed limit was put in jeopardy in the 70’s when they went to a 55 mph limit. Don’t make the same mistake.
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RightLaneDriver 11:50PM (12/25/2008)
This entire argument revolves around what is your motivator for driving the speed limit.
If it is for the purpose of safety, I can't say for or against if driving at the the posted speed limit is going to make for a safer commute (although general physics leads me to think that it would be safer to travel at a posted speed instead of an elevated speed).
However, if it is for the purpose of fuel economy or the reduction of CO2, then I believe that benefits can be reaped by sticking to what is posted on the signs. Check out the 2nd tip shown at the FuelEconomy.Gov site for more (http://fueleconomy.gov/feg/driveHabits.shtml). As you will see, fuel economy starts tip dip after 60 MPH, so it would be logical to think that the faster you go, the lower your MPG would be.
Of course, there are cars that are going to peak at higher MPH than what FuelEconomy.gov shows. However, if we take their data as a representation of what the average vehicle would experience, there is benefit to be gained in average.
I write all of this with a bit of bias, as I'm the admin of the source of the article (http://www.drivethespeedlimit.net). But, I can tell you that I gladly drive in the right lane at a constant speed (which contributes to greater fuel economy) with the knowledge that I'm being as green as I can be on my commute.
Ryan
MikeW 5:15PM (12/25/2008)
The speed limit is what people drive.
It should be set to the 85th - 90th percentile of free flowing traffic.
Transmission technology is the equalizer, and here the American companies have been sitting on their collective hand for the past thirty odd years.
Look at the new 911 with PDK (seven speed double clutch transmission)
http://www.caranddriver.com/content/download/133251/1824007/version/1/file/911vM3_Powertrain.pdf
Top doesn't have to be in top gear.
7th gear is good for 155mph (250kph) but not much more.
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BrianM 5:38PM (12/25/2008)
"should" is not part of the equation here boys.
Drive the speed limit OR LESS. I do, and I live in Wyoming where a round trip to the mall or Sams club is 300 miles. I set cruise on 65 indicated (works out to 61~62 real mph)....
It does NOT matter what "you" think the speed limit should be, it's set where it's set and going over it is breaking the law. I wish penalties were MUCH more strict (right on up to loss of license) as I see it as a "gateway crime". People not see the harm in speeding (no integrity), they see nothing being done about it and act worse and worse in all other areas of life, continually thinking that there is no accountability for their actions. Parking in handicap posts, or no parking zones, driving on the shoulder, not allowing pedestrians to cross at crosswalks, etc...
If "you" don't like where it's set, then do something about it or go somewhere else where the limit is more to your liking. In the mean time, get off my as^^^bumper, m'kay? The more you crowd me, the slower I'm going to drive.
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jpm 7:13PM (12/25/2008)
Don't be such a stickler.
I think you need to bitch less when you're doing something much more ignorant then breaking arbitrary speed limits: driving 300 miles to support your local Chinese retailer. Or don't you mind sending all your money to China and the Middle East?
ale 9:54PM (12/25/2008)
driving below the limit just creates congestion just helping the cause of burning of more gasoline while traveling slower, doin the world a huge favor
steve 7:03PM (12/26/2008)
Everyone driving slow does not increase congestion, if anything it reduces it. Think about fluid flow. If you have a pipe with a fixed diameter you can only pump so much water through with diminishing returns with an increase in pressure.
I will give you that a single vehicle in a lane going slow increases congestion in that it acts like a taper in the pipe.
In reality the speed limits on high traffic highways need to go down to reduce urban congestion.
Your big causes of congestion are things that routinely reduce the diameter of the pipe (busy exit, car accident, etc.).
gorr 6:02PM (12/25/2008)
Don't be scare by ' cautious' people about security, you've been caught on sept 11 2001, that's enouph now.
70 m.p.h is reasonable at night and in snow storm and 80 m.p.h in the day on dry is reasonable too. Slow poke on liver pills should go 65 m.p.h in the right lane and put their flashers if they drive below the safe margin of 65 m.p.h. There a lot of old pokes with old pick-ups or gm s.u.v that are dangerous, so they might remain in the right hand lane. The left lane can accomodate, mazda 3, civics at 80 m.p.h, so that way it's better for traffic because you are less time on the highway giving space to others.
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Pete J 7:45PM (12/25/2008)
As I have said elsewhere, we need to have a fuel tax that truly kicks in when people exceed a certain fuel usage - say 400 gallons per driver. Rebate those drivers that use less. Every licensed driver gets $800 when they file their taxes. Everybody pays a $2.00 a gallon excise tax at the pumps.
If I drive a Ford 3/4 ton 4X4 Pickup that I baby and light foot it from stops, dont drive over 55 and go 4000 miles a year at an average of 15 MPG - I am Green - I burn only 267 gallons of gas therfore I pay $534 tax at the pump but with the $800 rebate - I net $266 for conserving energy. If on the other hand, I drive a Prius - mostly on the highway at 90 MPH and leadfoot it everywhere and go over 20,000 miles (I love to live far away from work but hate the long drive times) per year at 35 MPG because of my bad driving habits - I would consume 571 gallons of fuel and pay $1143 excise tax at the pump - so after my $800 rebate, I end up paying $343 for being an energy hog.
This approach allows the driver to decide how far they need to travel. what size car, and how hard they want to drive. People who want to save fuel will find that they and their driving habits are more important a factor than the kind of car they drive to reduce the fuel usage.
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texmln 11:34PM (12/25/2008)
Yet another one who thinks more taxes are some magic pill that makes everything alright...
Did you miss Econ 101? Not only do taxes not provide any benefits, they are a dead weight loss - a net negative for everyone.
The best policy is to let people decide what they want for themselves and let them pay the price or reap the benefits of their own decision without government interference. It's your best bet in the long run... because it won't always be people who happen to agree with you making the income redistribution decisions and determining what to tax.
eliot 12:25AM (12/26/2008)
Haha! Funny, I experimented with driving 55 when gas was $3+ a gallon and nearly got run off the road in 60mph speed zones, and they go as high as 70 here. Speed limit signs are a joke.
Coming home for Christmas I was doing 70 in a 55 and got passed by 2 marked patrol cars, one was a County patrol car (in his jurisdiction) and the other was a highway patrol/state trooper. Save your life, drive with the flow of traffic, if you want to be green do it in a hybrid or TDI.
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RK 12:59AM (12/26/2008)
I'm not sure where you live, but I live in Chicago (which has some pretty aggressive drivers) and I can drive without incident or pressure in the right lane at the posted speed limit. And I'm typically not alone in doing so.
I don't think there needs to be the advocation that you drive deliberately slow relative to the overall flow of traffic in a case of a 2 lane road. But, if the opportunity presents itself and if you can cruise along at what the speed limit is, all the better for the land around us.
Joe 1:36AM (12/26/2008)
The most efficient speed to travel at varies from vehicle to vehicle, and arbitrarily choosing 55 isn't going to make the world a greener place. Build better cars for that.
What would be nice is dynamic speed limits which adjust based on driving conditions. On bright sunny dry days with low traffic conditions, speed limits could push 80 or 90. In cases of inclement weather, darkness or high traffic volume, it would lower to adjust for these conditions.
It's not a new idea, and it exists in a few places such as (I think) the autobahn, but it takes some serious investment to make it work.
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nick 12:40PM (12/26/2008)
55 is of course not the most efficient speed for all vehicles, I believe that it was set at 55 for tractor-trailer trucks. The more aerodynamic your car is, and depending upon your car's gearing (do you have Overdrive?), you'll see your efficiency peak at a higher speed.
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RPM 8:20PM (12/26/2008)
For me and the car I drive if I go the speed limit it would lower the MPG (not by a lot but its still less). If you take into account the inertia you build up going down a hill you waste a lot of energy breaking to stay within the limits..I live in an area where there are a lot of rolling hills and i can get about 4 to 5 MPG better by being a smart driver in terms of utilizing momentum to its fullest potential (within reason). Even going up to 80 MPH i will get close to 35 MPG in my car...not to bad for a V6. Driving the speed limit at all times in the same area over a few weeks (I tested this) yields about 28 to 30 MPG.
I also agree it depends on the car you have (transmission) and overall driving habits.
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