# Driving 5 miles under the speed limit **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [April 26, 2015, 10:48pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599 "2015-04-26T22:48:19Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [April 27, 2015, 5:08am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/21 "2015-04-27T05:08:45Z")
And turn on your left-turn signal. ---
**Author:** ![Tibby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tibby/32/17030_2.png) [@Tibby](https://boards.straightdope.com/u/Tibby)\ **Post date:** [April 27, 2015, 5:15am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/22 "2015-04-27T05:15:30Z")
**Robert163** , I wish to encourage you to leave as small a carbon footprint on planet Earth as possible. Driving 5 miles below the speed limit is certainly one (feeble) attempt to reduce the size of your foot, but, really, let’s be honest, that’s a very tiny, half-hearted attempt to save your planet—the planet that loves you and pleads for your help, right? As others have mentioned, you definitely don’t want to reproduce and you must move into a large city. In the city, you won’t need any automobile at all. And, interestingly, studies show that driving zero miles per hour is actually better for the environment than driving 5-miles below the speed limit. In the city you may also forgo such carbon-footprint wasteful things like electricity, water and sewerage. And purchasing planet-killing items like groceries and clothing are strictly verboten, too. Remember, you are a free-bird savior—you scoff at material things! I don’t think there’s a name for this type of homeless urban planet-saver, so let’s just call you **Robert163, Earth-Warrior**. You will be a carbo-superhero who lives in the alleys of downtown NYC in a cardboard box (a recyclable cardboard box, of course) and who, by day, requests life-sustaining hand-outs from fellow city-dwellers (you may wish to obtain an old hat to collect your tithing). And, on the companionship front, if you’re a pet-loving person such as me, you will enjoy the many whimsical encounters you’ll have with the city pidgins and rats (rats are quite cuddly on cold nights, you know). But, perhaps best of all…you will be helping me, your Straight Dope pal. You see, I’m a carbon Bigfoot and a hard-core atheist. However, shortly before I die, I plan to find Jesus (he’s always in the last place you look) and convert to Southern Baptist. When I take the escalator up to St. Peter at the Pearly Gates, I anticipate the conversation to go something like this: Me: _hey, Pete, how’s it hangin’?_ Peter: _Low and to the left, Tibs. But, on a serious note, I can’t, in good conscious, admit you into heaven, homie, ‘cause you ain’t been a very Earth-responsible dude when you was alive._ Me: _Whatcha talkin’ 'bout, bro?_ Peter: _I mean, you’ve driven a big-ass SUV since you were 10 that gets 1/2 miles to the gallon; you’ve kept your thermostat at 88 degrees Fahrenheit in the winter and 52 degrees Fahrenheit in the summer; you’ve shot and killed bald eagles and manatees for target practice; you’ve…_ Me: \*yeah, yeah, yeah…you can stop right there, Pete, my boy. Sure, I’ve left a big ol’ carbon footprint on Earth, but, on the other hand, I encouraged **Robert163** to go in the opposite direction and leave no carbon foot print whatsoever. So, by my way of thinking…he and me kind of cancel ourselves out—and, therefore, I’ve earned admittance to heaven. \* Peter: [furiously pushing buttons on his calculator]_…hmmmm…carry the 4…subtract 2…_[/furiously pushing buttons on his calculator]. \*Well, Goddamn it, you’re right, Tibs. My apologies. Here’s your first class boarding pass to eternal bliss and salvation! Don’t take any wooden nickels. \* Me: _Tell the angels to put a thin mint on my pillow and stock the mini-bar with lots of booze, Peaty, were gonna throw a hell of a good party tonight!_ …Just pulling your leg **Robert163** , you seem like a nice, sincere guy…if just a bit overly earnest. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [April 27, 2015, 5:15am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/23 "2015-04-27T05:15:56Z")
> [@jezzaOZ](#): > > All modern speedometers are calibrated to over-read the speed by several percent. So an indicated 55 is probably closer to 50 actual. Do you have a cite for that? I find that various GPS devices align very well with the indicated speed of everything I’ve ever driven (all modern, 2001 or later vehicles). I don’t mean the built-in GPS, but things like Garmin and now telephones. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 27, 2015, 6:31am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/24 "2015-04-27T06:31:54Z")
> [@Hentor\_the\_Barbarian](#): > > Why not double your fuel efficiency and drive 10 mph below the speed limit? Or travel everywhere in reverse - so you’re giving something back. ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [April 27, 2015, 8:57am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/25 "2015-04-27T08:57:17Z")
> [@tibby or not tibby](#): > > **robert163** , i wish to encourage you to leave as small a carbon footprint on planet earth as possible. Driving 5 miles below the speed limit is certainly one (feeble) attempt to reduce the size of your foot, but, really, let’s be honest, that’s a very tiny, half-hearted attempt to save your planet—the planet that loves you and pleads for your help, right? > > As others have mentioned, you definitely don’t want to reproduce and you must move into a large city. In the city, you won’t need any automobile at all. And, interestingly, studies show that driving zero miles per hour is actually better for the environment than driving 5-miles below the speed limit. > > In the city you may also forgo such carbon-footprint wasteful things like electricity, water and sewerage. And purchasing planet-killing items like groceries and clothing are strictly verboten, too. Remember, you are a free-bird savior—you scoff at material things! > > I don’t think there’s a name for this type of homeless urban planet-saver, so let’s just call you **robert163, earth-warrior**. You will be a carbo-superhero who lives in the alleys of downtown nyc in a cardboard box (a recyclable cardboard box, of course) and who, by day, requests life-sustaining hand-outs from fellow city-dwellers (you may wish to obtain an old hat to collect your tithing). And, on the companionship front, if you’re a pet-loving person such as me, you will enjoy the many whimsical encounters you’ll have with the city pidgins and rats (rats are quite cuddly on cold nights, you know). > > But, perhaps best of all…you will be helping me, your straight dope pal. You see, i’m a carbon bigfoot and a hard-core atheist. However, shortly before i die, i plan to find jesus (he’s always in the last place you look) and convert to southern baptist. > > When i take the escalator up to st. Peter at the pearly gates, i anticipate the conversation to go something like this: > > Me: _hey, pete, how’s it hangin’?_ > > peter: _low and to the left, tibs. But, on a serious note, i can’t, in good conscious, admit you into heaven, homie, ‘cause you ain’t been a very earth-responsible dude when you was alive._ > > me: _whatcha talkin’ 'bout, bro?_ > > peter: _i mean, you’ve driven a big-ass suv since you were 10 that gets 1/2 miles to the gallon; you’ve kept your thermostat at 88 degrees fahrenheit in the winter and 52 degrees fahrenheit in the summer; you’ve shot and killed bald eagles and manatees for target practice; you’ve…_ > > me: \*yeah, yeah, yeah…you can stop right there, pete, my boy. Sure, i’ve left a big ol’ carbon footprint on earth, but, on the other hand, i encouraged **robert163** to go in the opposite direction and leave no carbon foot print whatsoever. So, by my way of thinking…he and me kind of cancel ourselves out—and, therefore, i’ve earned admittance to heaven. \* > > peter: [furiously pushing buttons on his calculator]_…hmmmm…carry the 4…subtract 2…_[/furiously pushing buttons on his calculator]. \*well, goddamn it, you’re right, tibs. My apologies. Here’s your first class boarding pass to eternal bliss and salvation! Don’t take any wooden nickels. \* > > me: _tell the angels to put a thin mint on my pillow and stock the mini-bar with lots of booze, peaty, were gonna throw a hell of a good party tonight!_ > > …just pulling your leg **robert163** , you seem like a nice, sincere guy…if just a bit overly earnest. lol :d:d:d ---
**Author:** ![jezzaOZ](https://avatars.discourse-cdn.com/v4/letter/j/a9a28c/32.png) [@jezzaOZ](https://boards.straightdope.com/u/jezzaOZ)\ **Post date:** [April 27, 2015, 9:39am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/26 "2015-04-27T09:39:59Z")
> [@Balthisar](#): > > Do you have a cite for that? I find that various GPS devices align very well with the indicated speed of everything I’ve ever driven (all modern, 2001 or later vehicles). I don’t mean the built-in GPS, but things like Garmin and now telephones. Australian Design Rules - not different to European and presumably American rules says (paraphrased) _The current Rules disallow under-reading, and permit over-reading by up to 4kmh + 10%._ [[http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf](http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf)]([http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf](http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf) Australian Design Rules) ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [April 27, 2015, 11:22am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/27 "2015-04-27T11:22:29Z")
Get a Segway, dude. For some reason that’s how I imagined you got around. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [April 27, 2015, 11:44am UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/28 "2015-04-27T11:44:53Z")
I used to drive on the highway with my cruise control set at the maximum speed that I could travel at without being booked. Pretty clever I thought; max speed, no tickets however a fair bit of braking and overtaking. About two years ago I got on the highway and was fooling around with CDs and had the cruise control set just below the speed limit. When I was ready to concentrate on driving I decided to leave it like that for a while. Since that day I have never resumed my old method. The lower setting adds about 10 minutes to my trip but lowers the level of angst by about 90%. Admittedly it is a multilane road so I don’t get in anyone’s way and the occasional overtaking move is accomplished with ease. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [April 27, 2015, 12:07pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/29 "2015-04-27T12:07:10Z")
> [@Robert163](#): > > I wish I could move back to NYC, I really really do. Ditto. You’d do a lot more for the environment, to not drive at all. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [April 27, 2015, 12:20pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/30 "2015-04-27T12:20:12Z")
When I have tested my odometer against mileage markers, it always seemed to register between 2% and 3% high. I have done that over distances of several tens of miles, so it ought to be accurate. Once in a while you hit a measured 5 mile stretch and I have tried to measure the speedometer directly. It is hard to keep accurately to a fixed speed (now I have cruise control, but I haven’t seen a measured course since) but as far as I can tell that 2-3% seems to hold. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 27, 2015, 12:24pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/31 "2015-04-27T12:24:44Z")
> [@SenorBeef](#): > > Most cars are most efficient at 40-45 mph. Any slower than that and you lose more to rolling resistance than wind resistance. Rolling resistance _and_ wind resistance both decrease with decreasing speed, all the way down to zero MPH. The problem is that as engine load decreases (with decreasing speed), the engine becomes less and less efficient. So you’ve got this battle going on between the vehicle’s mechanical power requirement (wind/tire drag) and the efficiency with which that power is provided; for most vehicles, 40-50 MPH represents the crossover point where the best fuel economy is achieved. Lots of studies have been done on vehicle fuel economy, and that’s just one aspect. Things get more complicated with city driving, which involves a lot of speeding up and slowing down to deal with turns and traffic control devices. One study I recall found that for city driving, fuel economy is inversely correlated with “microtrip” time - that is, the time between each start and stop during your trip. Light turns green, you accelerate, and come to a stop at the next red light; that’s a microtrip, and if it’s over quickly, then it’s because it was a short distance, and/or you were a wild man with the gas, accelerating quickly and hitting a high top speed, and then pissing away all that energy with the brakes at the next stop. Want good city fuel economy? Accelerate gingerly when the light turns green, and keep your peak speeds down. Anticipate upcoming traffic lights so that you can hang onto some of your speed instead of getting there fast and coming to a complete stop. Want good highway fuel economy? Steady as she goes, and keep your speed down. [More info here.](http://en.wikipedia.org/wiki/Energy-efficient_driving) > [@jz78817](#): > > it’d be much more effective moving closer to where you work. This. The commute to one’s job is something most people do ten times per week. If you choose your residence such that you chop ten miles out of it, then you cut out 5200 miles of driving every year. If you get close enough so that you can ride a bicycle to work from time to time when the weather is nice, then it’s a double-bonus: very low carbon footprint, and your body gets some exercise. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [April 27, 2015, 12:30pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/32 "2015-04-27T12:30:22Z")
> [@jezzaOZ](#): > > Australian Design Rules - not different to European and presumably American rules says (paraphrased) > > _The current Rules disallow under-reading, and permit over-reading by up to 4kmh + 10%._ > > [[http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf](http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf)]([http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf](http://rvcs-prodweb.dot.gov.au/files/ADR%201803.pdf) Australian Design Rules) Not trying to be an arse, but that doesn’t actually indicate that over-reading is required, nor indicate any measure of cars that actually do over-read when tested. I will consult my company’s design guidelines tomorrow, and they should be global. (In all my years, this is the first I’ve ever seen the _indent_ tag. Cool! I can stop abusing unordered lists.) I’d like to think (but I could be wrong) that having put a man on the moon, we can do a lot better than 120 + 4 + 12.4 = 136.4 showing on the speedo while only travelling 120. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 27, 2015, 1:04pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/33 "2015-04-27T13:04:04Z")
> [@Balthisar](#): > > Not trying to be an arse, but that doesn’t actually indicate that over-reading is required, nor indicate any measure of cars that actually do over-read when tested. True, but if your allowed range if -0% to +10%, then your safest target is going to be +5%. ---
**Author:** ![Aquadementia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aquadementia/32/555_2.png) [@Aquadementia](https://boards.straightdope.com/u/Aquadementia)\ **Post date:** [April 27, 2015, 1:27pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/34 "2015-04-27T13:27:28Z")
> [@Hentor\_the\_Barbarian](#): > > Why not double your fuel efficiency and drive 10 mph below the speed limit? To double it he would need to drive a distance equal to where he was going but in the opposite direction then walk there. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [April 27, 2015, 1:30pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/35 "2015-04-27T13:30:50Z")
> [@chacoguy](#): > > If you think of all the cars on the highway as a system, there’s probably going to be more gas burned by people speeding up to go around you. Also consider that, even if you drive the speed limit, you’re still going to have people passing you. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 27, 2015, 1:55pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/36 "2015-04-27T13:55:28Z")
> [@Ethilrist](#): > > Also consider that, even if you drive the speed limit, you’re still going to have people passing you. All you can do it realty minimize this, which usually involved driving casually over the limit. ---
**Author:** ![Hentor\_the\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/h/8edcca/32.png) [@Hentor\_the\_Barbarian](https://boards.straightdope.com/u/Hentor_the_Barbarian)\ **Post date:** [April 27, 2015, 1:57pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/37 "2015-04-27T13:57:54Z")
> [@Aquadementia](#): > > To double it he would need to drive a distance equal to where he was going but in the opposite direction then walk there. Ah! But what if he were to walk backwards? ---
**Author:** ![Tibby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tibby/32/17030_2.png) [@Tibby](https://boards.straightdope.com/u/Tibby)\ **Post date:** [April 27, 2015, 1:58pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/38 "2015-04-27T13:58:48Z")
> [@kanicbird](#): > > All you can do it realty minimize this, which usually involved driving casually over the limit. You’re driving while you texted that, didn’t you? 😃 ---
**Author:** ![Aquadementia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aquadementia/32/555_2.png) [@Aquadementia](https://boards.straightdope.com/u/Aquadementia)\ **Post date:** [April 27, 2015, 2:09pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/39 "2015-04-27T14:09:22Z")
> [@Hentor\_the\_Barbarian](#): > > Ah! But what if he were to walk backwards? I think that would violate the laws of thermodynamics, like a perpetual motion machine. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 27, 2015, 2:27pm UTC](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599/40 "2015-04-27T14:27:51Z")
> [@Tibby or Not Tibby](#): > > You’re driving while you texted that, didn’t you? 😃 LOL, sending you the bill for new keyboard 😃 [Previous page](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599.md?page=1) [Next page](https://boards.straightdope.com/t/driving-5-miles-under-the-speed-limit/718599.md?page=3)