By on December 26, 2008

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44 Comments on “You Can’t Drive 55; But Should You?...”


  • avatar
    aggrazel

    Looks like I’m saving 17 minutes a day, thats pretty significant to me. Thanks for showing me the savings !!

  • avatar
    bunkie

    Last week I drove 1100 hours in a 48 hour period. Averaging 66mph saved me more than two hours. That’s enough time to read and laugh at several of these idiotic “studies”.

  • avatar
    enderw88

    You mean, the faster I drive, the more time I save? Amazing, and I thought it just fun!

  • avatar
    thalter

    No big surprise here. Every 10MPH increase saves you about 10 minutes/hour. Doing 80 instead of 55 turns an 8-hour trip into a 6-hour trip.

    Totally worth it, IMO. Time is money – I’ll gladly save a few hours, even if it costs me more in gas.

  • avatar

    United States rural speed limits usually match legislated numbers. Coincidence? No. They are arbitrary and capricious.

    Speed is a time vs. cost trade off, a personal decision. Only a stooge would say that an arbitrary and capricious policy is the correct trade off for everybody.

    The government’s job is to protect us from outliers, not to make decisions for us.

  • avatar
    thalter

    I find it exceptionally interesting that there is an entire site dedicated to driving the speed limit!

  • avatar
    Strippo

    That chart was meant to be applied to daily commuting and not long trips. Of course, many of us only wish we could “speed” during our commutes, so the point is still lost on me.

  • avatar
    Robstar

    I don’t know about you guys, but my reverse commute to work on the main road next to my house (speed limit 30) has the lights timed to hit green about 40mph. If you go 30 you hit almost every red light possible. I’ll stick to 40 as long as no cops are around & conditions permit, thanks.

    The other thing the author doesn’t take into account is traffic in large urban areas.

    Maybe you save only 5 to 10 minutes in real SPEED, but what he is neglecting is the fact of traffic pickup as rush hour gets heavier.

    Say it takes me 40 minutes @ 80mph to get somewhere (say, commute home starting @ 4:30pm). That is 53 miles or so. I’d get home at 5:10.

    Now if I traveled the same at 55mph. That would be 57 minutes instead of 40, assuming ALL other variables are the same. I can tell you that TONS of people get around here get off at 5:00-5:30, so trying to get home at 5pm, so that 17 minute faster might actually turn into 30 minutes faster because you will hit more traffic near the end of your trip.

    I really think he is not taking all traffic variables into account with his little chart.

  • avatar
    Pch101

    That chart was meant to be applied to daily commuting and not long trips.

    The guy writing the blog is nostalgic for the 55 mph limit. His goal is to save fuel and reduce CO2 emissions.

    I know that I’m blowing the punchline here by pointing this out, but what is funny about this chart is that the blogger who compiled it believes that this data will encourage you to slow down. Yet all of us here are using it as a justification to drive faster. Talk about unintended consequences…

  • avatar
    Strippo

    I know that I’m blowing the punchline here by pointing this out, but what is funny about this chart is that the blogger who compiled it believes that this data will encourage you to slow down. Yet all of us here are using it as a justification to drive faster.

    Right, in part because you’re taking the chart out of its intended context, and in part because the chart exceeds that intended context to an absurd degree.

  • avatar
    Driver23

    Those 7 additional minutes of sleep in the morning are hugely important for my mental health.

  • avatar
    Michael Ayoub

    There’s an even better benefit to driving faster: awareness. Alertness.

    The slower you drive (for a longer period of time, obviously), the less concentrated you are. It’s more boring. It’s tiring.

    I’d rather not drive on the road with a whole bunch of people busy saving the planet while being half awake.

  • avatar
    Michael Ayoub

    “Although I know the time that I would save by speeding a bit over 55 is minimal in the grand scheme of things, I figured I would put my engineering degree to work and figure out the exact numbers. As I might drive different distances at different speeds, I decided to calculate the time saved and various distances and MPH’s. And, as the results showed, there wouldn’t be all that much time saving on my daily commute by speeding.”

    Wow.

    I can’t wait until I get my degree so I can have skills like this!

  • avatar
    AuricTech

    Did y’all notice the poll on this blog?

    Current Poll

    How fast do you go relative to the speed limit?

    * I go the speed limit
    * 5 miles over the speed limit
    * 10 miles over the speed limit
    * 20 miles over the speed limit
    * More than 20 miles over the speed limit
    * I drive a Buick. I got [sic] 10 miles under the speed limit!

  • avatar
    Lumbergh21

    It’s people like this who run the state of Oregon and set the speed limit in the desolate Eastern half at 55. Personally, I prefer to get through those straight boring stretches of nothing as fast as possible. Luckily, I’ve only seen one cop over several trips through Eastern Oregon and it was at a rare time when I was only going a few mph pver 55. What’s really funny is the speed limit on the same highway on California is 65; so, it obvioulsy has nothing to do with the road itself.

    Second, this is meant to encourage people to drive 55 all the time; thereby, clogging our freeways even more. These are the idiots who are driving 10 mph below the speed limit and 15+ mph below the general flow once you get around them.

  • avatar

    As the original poster of the chart (and I would never have described it as a “study….that was someone else’s description), I find the responses…..interesting.

    For me, it is a trade-off between a little bit of extra sleep or a little less time in your car versus a little less gas burnt (theoretically) or a little less CO2 burped out (theoretically) or a little less stress while driving (depending on how you feel towards driving).

    Because I’m a bit of an eco-nut, and because gas prices were killing me when I first started this, I’ve opted to drive slower.

    Would that change on 1000 mile trip to Texas? Probably. The time savings for me by going 75 versus 55 would be worth the extra money I’d pay in gas.

    I can be realistic that the impact has shifted much more to the environmental now versus back when gas was $4.50 a gallon. But, as I am a bit of an Eco-Geek, it still makes sense to me.

    Because of the fact that I’m friends with some other eco-geeks, the have looked at the chart and thought that the numbers support slowing down a bit for the green reasons. Not surprisingly, I have friends who think I’m f’ing crazy for doing it too.

    At the end of the day its personal preference. To each their own, and I understand completely why people would take a contrarian view to what I’m doing. And I’m perfectly fine with that.

  • avatar
    tedward

    fantastic…I saved somewhere around 45-50 minutes last night driving back downstate.

    And who thinks that the 55 limit was ever a good thing? Let’s see…more speeding tickets, more frustration, less fun, and, frankly, not much of a difference in people’s actual driving habits or the risk they will crash. No thanks. As far as fuel savings go I can choose to drive like a palsied senior (is that not polite?) if I want to save that 5mpg, but I really don’t know anyone that does.

    Maybe he should campaign for a return to bias-ply tires, that’d slow everyone down. Of course, we’d lose mpg right there, but it’s the only way I see this ever actually happening.

  • avatar
    ihatetrees

    I’m surprised there’s not another chart detailing carbon usage for a trip of x miles at y average speed.

    Then again, most peoples’ time is worth far more than the costs of gas and environmental damage.

  • avatar
    alex_rashev

    Let’s put my engineering skills (acquired in 2nd grade) to work.

    Say, you’re flipping burgers for $7.50 an hour, a bottom-of-the-barrel wage around here where I live.
    Furthermore, let’s assume you’re driving a 15-year-old Corolla/Sentra/Civic (which you should be if you’re flippin’ burgers), which gets roughly 35mpg at 55 and [actually way over] 25mpg at 85.
    Better yet, let’s assume it’s May of 2008 and gas is 4 bucks a gallon.

    If your daily commute is 30 miles (15 miles both ways), you need 1.2 gallons at 85, or .86 gallons at 55, which at $4 a gallon translates into a $1.37 difference.

    Now, this saves you 11.6 minutes according to the chart, meaning you could earn $1.45 by clocking out 11 minutes late every day. Total saved every day by driving fast: 8 cents a day plus the valuable experience from flipping burgers.

    These savings grow into double-digit dollar numbers when you start talking about a middle-aged well-off professional, and reduce gas price to the $2 that we see now.

    There are far better ways to save the earth than driving slow. Unfortunately, eco-nazis don’t like nuclear power, or trains, or diesels, or human beings for that matter.

    I would never go to Atlanta or New York doing 55 all the way. Something about the 2-3 hours of my life that I’ll never get back, no matter what the price is.

  • avatar

    Would that change on 1000 mile trip to Texas? Probably. The time savings for me by going 75 versus 55 would be worth the extra money I’d pay in gas.

    Why not the daily commute? A 10 minutes savings per day is 40 hours per year–an entire workweek!–assuming 48 hours of 5 day a week working time per year.

  • avatar
    bunkie

    ‘…and I would never have described it as a “study….that was someone else’s description’

    My other hobby is reading studies about humor and why it is funny.

  • avatar
    John Horner

    For relatively short local drives, going faster does almost nothing useful for you. Over longer distances, however, the time differences are huge. At least once a year I find myself on a car trip of over 1,000 miles, in which case an extra 10 MPH means hours saved. Those trips make me long for the autobahn. Imagine doing San Francisco to Seattle at 100 MPH, which works out to about 8 hours. That would be much more enjoyable than the 12 hours it takes doing the speed limit.

    No-Tell Motels would hate it.

  • avatar
    Hippo

    To me it isn’t about the fuel mileage or the time, it’s about the speed that feels right at any given time.

    In the car usually between 10 and 20 over the limit.

    On the bike a little faster then the flow of traffic.
    Speed cameras are a death sentence for bikes, it is too dangerous to be unable to speed up to separate from traffic.
    99% of cops recognize this and in most cases would not pull bikes over unless they were riding stupid. The cameras have no judgment, they would let a total idiot go just because he is within the speed limit.

  • avatar
    findude

    A few posters have commented on the importance of taking other variables into account.

    Over the years, whenever I’ve had a new commute I’ve run a control chart for a few weeks. I keep a small notepad in the car and note the date, time I left, and time I arrived. I try to keep the same driving habits (usually slightly faster than traffic but not notoriously so) throughout the period.

    A month of data will tell you the best time to leave home and to leave work in terms of the shortest commute time.

    I have concluded that some commuting situations are outliers no matter what: Friday evening, the first few days after school (K-12) starts in the fall or ends in the spring, and very unusual weather. No amount of data will help predict commute time in those situations.

    I also found the best remedy is to get a good CD changer or an iPod adaptor so that I can at least enjoy tunes I like when I do get stuck in traffic. Nothing is worse than listening to the radio during rush hour.

  • avatar
    Dimwit

    Just to add some datum: 55 mph is not the “most efficient speed” as assumed. That’s an arbitrary limit set by the pols. “The most efficient speedlimit” is complex and varies by vehicle. Size of the engine, wind resistence and gearing all contribute and small, efficient cars with slippery shapes can go much faster as their most efficient speed. A VW TDI is somewhere around 75 mph.

    Less speed and you are not maxing out that combustion of precious fuel.

  • avatar
    Pch101

    Size of the engine, wind resistence and gearing all contribute and small, efficient cars with slippery shapes can go much faster as their most efficient speed. A VW TDI is somewhere around 75 mph.

    This is not at all true when the issue is one of highway speeds.

    At higher speeds, fuel economy is inversely related to the headwind that you create when you bury your foot into the accelerator. Wind resistance burns fuel, and speed creates wind. For a car to get better fuel economy at a 75 mph cruise than at 50 mph, it would need to violate laws of physics.

    The most efficient travel speeds are between 20-40 mph, depending upon the car, driven in the highest gear possible without lugging the motor. Those speeds might drive you crazy, but you’ll use less fuel on the way to therapy.

    http://www.timesonline.co.uk/tol/driving/article4107764.ece

  • avatar
    Dynamic88

    I drive 6 miles to work. I usually drive about 5 under, because of darkness. It seems I’m loosing no significant time at all.

  • avatar
    alex_rashev

    Pch101,

    It appears to me that the cars they picked were all city runabouts with small engines. The diesel example is also an outlier – diesels are rather efficient at low power outputs due to low pumping losses. I bet neither of those had AC or lights on, either.

    The average american commuter car gets pretty good gas mileage anywhere between 40 and 80mph. My Sentra used to get 28-30 city, 37-39 when driven at 55 average, and 33-35 when driven at 90+.

    On the other hand, both of my short-geared two-seaters can get 28mpg when cruising at 60 or doing light city driving, but barely manage 24 when blasting down the highway at 90mph. YMMV.

    Electric cars, of course, will screw up the equation completely – those can do 15mph all day and get insane range, but can’t manage a medium-distance inter-city trip at a relatively pedestrian speed of 90mph. Perfect for commuting, IMO.

  • avatar
    tedward

    Pch101…you’re definitely right about the wind resistance relationship, but it’s almost besides the point trying to pin down the most efficient cruising speed. Really the aim should be for the most practically enforceable and safe speed that American drivers will tolerate. And 55 ain’t it.

    I’d even compare it to prohibition movement: no one will obey the rule, tons of people get caught up with fines and punishment as a result and overall it causes more grief than good (and that should be the only relevant information that a legislator needs). We’ll see though, if speed cameras keep spreading it’ll give politicians a real incentive to ignore our best interests (lobbying money indeed) and whatever departments are overseeing these purse-strings will develop their own influence to prepetuate the cycle. And thanks to the current prohibition movement we know exactly where that will lead…to lots of Americans getting hosed with no upside.

  • avatar
    Pch101

    It appears to me that the cars they picked were all city runabouts with small engines

    Whether or not that’s true is irrelevant. The laws are physics are what they are. Engine size doesn’t alter those at all.

    Here’s a challenge for you — the European version of the EPA rating performs two highway tests, one at 100 km/h (62 mph) and another at 120 km/h (75 mph).

    Use that to find one example of a car that gets better fuel economy at 75 mph than at 62 mph. (Allow plenty of time, because you aren’t going to find one.)

    I like driving quickly as much as the next guy, but facts are facts, and fuel consumption increases dramatically above 40-50 mph or so. Gearing and aerodynamics can only reduce the loss incurred as speeds increase, those changes don’t cause a inverse relationship that can fight science.

    Highways are designed to move people and goods quickly and efficiently. That does not mean that the speeds that are optimal for humans and their stuff are the same speeds that burn the least amount of fuel.

  • avatar
    benders

    I think Dimwit was talking about brake specific fuel consumpiton. Depending on engine size, geometry, and speed, your BSFC may drop as you increase speed.

    Apparently someone has done some research with this:
    http://upload.wikimedia.org/wikipedia/commons/a/a9/Fuel_economy_vs_speed_1997.png

  • avatar
    Lumbergh21

    I agree with PCH101. The only question is whether a particular car gets better mileage in 4th gear at the minimum speed without lugging the engine or in 5th gear at the minimum speed without lugging, etc. With each of the last two cars I’ve had, I would bet that the most efficient speed would have been in the range of 35 to 40 mph in 5th gear. In a corvette, it might be 65 mph in 6th gear though. So, to make a blanket statement, as some have done in the past, that a 55 mph speed limit is about saving lives (another issue) and saving gas is IMO a falsehood. The speed limit was reduced to 55 mph because that was a number the politicians and bureaucrats thought they could get away with.

  • avatar

    If people want to drive 55, fine. But it would be micromanagement to enact 55mph speed limits in order to force reductions in carbon emissions. It would be far more efficient to enact a carbon tax and let people decide how they want to reduce their own spending on the carbon tax.

    Furthermore, a 55 mph limit could be counterproductive as far as reducing carbon is concerned. The reason is simple. Lower the speed limit, and more peopl ewill be ont he roads at any given time. As traffic density increases, speed decreases, and during rush hour especially, in the more crowded parts of the country, people will be crawling along at 15-25 mph. That will really push carbon emissions up.

  • avatar

    If people want to drive 55, fine. But it would be micromanagement to enact 55mph speed limits in order to force reductions in carbon emissions. It would be far more efficient to enact a carbon tax and let people decide how they want to reduce their own spending on the carbon tax.

    A voice of reason, as long as the carbon tax is revenue neutral, meaning income and other taxes decline as carbon tax revenue increases.

  • avatar
    mxhi5

    By driving faster you arrive at your destination sooner and therefore use less gas and emit less carbon. There must be a break even point at which you burn the least amount of gas and arrive at you r destination in the shortest possible time for your vehicle. What I’d like to know is can you tune your car for optimum time/burn for a given trip.

  • avatar
    dulcamara

    These fools believe my time has no value. They are wrong and have convinced me to drive faster.

  • avatar

    How about I lock this guy in a car governed at 55 and set him out to do my last vacation…NY to Montana.

    Enjoy Kansas.

    I bet if you did 45 you’d save more time.

    Please stay in the right lane. Thanks.

  • avatar
    Demetri

    What is really needed is a chart that shows how much longer your braking distances get at higher speeds. After you see how exponentially bad it gets as your speed increases, you may not want to go 90 so badly.

  • avatar

    How about I lock this guy in a car governed at 55 and set him out to do my last vacation…NY to Montana.
    Enjoy Kansas.
    I bet if you did 45 you’d save more time.
    Please stay in the right lane. Thanks.

    There has been no discussion of governing a car to 55, or any speed limit for that matter, and there has actually been the admission that there are instances (such as the long trips that you write up) where driving faster than what is posted may very well make sense. Ditto on the point that there is no admission that time has no value.

  • avatar
    John Williams

    Furthermore, a 55 mph limit could be counterproductive as far as reducing carbon is concerned. The reason is simple. Lower the speed limit, and more people will be on the roads at any given time. As traffic density increases, speed decreases, and during rush hour especially, in the more crowded parts of the country, people will be crawling along at 15-25 mph. That will really push carbon emissions up.

    In other words, the creation of an artificial incentive to public transportation.

  • avatar
    Kman

    Okay so first I’ll add my own contribution of thanks to the chart:

    Thanks to the chart, I now know that my old Boston-Montreal trip was about 100 minutes (over 1 1/2 hours) shorter since I did 75 ‘stead of 55.

    As for my other point. So, um, why 55? Only because it once was the speed limit? Why that number?

    By this logic — “55 is better for the environment” — why not 45mph? Why not 40mph or 50mph? Wanting to do something for the environment is admirable, but boy is this ever barking up the wrong tree. Find something useful to do for the environment.

    I’ll be driving 75-80 thank you very much.

  • avatar
    BMW325I

    If you want to help the environment make a bike out of wood and ride it everywhere. I will still be driving at 80mph.

  • avatar
    tankd0g

    How much time getting a ticket costs is really the only thing this chart should show because the rest is common sense.

  • avatar
    geeber

    DrivetheSpeedLimit is inaccurate…I don’t know of any state where the speed limit on rural limited access highways is 55 mph anymore.

    I just got back from a two-hour trip on the Pennsylvania Turnpike, where the official speed limit is 65 mph. I got stuck behind the one vehicle driving at 65 mph…and was passed by a steady stream of vehicles driving 75-80 mph. And I’m not talking about Corvettes and M-Series BMWs, either.

    The majority of people are voting with their right foot. We aren’t going to lower any speed limits, and the great majority of people are not going to drive slower. Most people have found other ways to save gas (note that gasoline consumption is down for the year in the U.S.).

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