# Why 15 mph and not 10 mph or 20 mph in school zones USA **URL:** \ **Category:** Factual Questions\ **Created:** [September 1, 2009, 1:14pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475 "2009-09-01T13:14:58Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [September 1, 2009, 7:21pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/21 "2009-09-01T19:21:38Z")
Around here it’s 15 mph at school zones with straight streets and a clear view or a hill approaching the school. It’s not an engineering decision, because all the schools get the same thing. Nobody has come up with a reason that speeds have had any reason for being what they are so far. **I’d like an example for any state that shows how they picked a speed.** I’m very good at speculating myself.🙂 ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [September 1, 2009, 7:41pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/22 "2009-09-01T19:41:08Z")
> [@Harmonious\_Discord](#): > > Nobody has come up with a reason that speeds have had any reason for being what they are so far. **I’d like an example for any state that shows how they picked a speed.** I’m very good at speculating myself.🙂 The radio commercials I’ve heard over the last couple years around the time school starts, reminding people of school zone speed limits, have stated that stopping distance at 20MPH is half of what it is at 30MPH. Whether this is true or not, I can’t say. I’d also like to quote a comedian I heard many years ago: “You see these signs in the Fall that say, ‘School’s In - Please Drive Carefully’. Then in the Summer you see signs that say, ‘School’s _Out_ - Please Drive Carefully’. When do we get a crack at these kids?!” ---
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [September 1, 2009, 7:59pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/23 "2009-09-01T19:59:57Z")
Did you ever try to drive at 10mph? It’s do-able but hard. ---
**Author:** ![TheMadHun](https://avatars.discourse-cdn.com/v4/letter/t/53a042/32.png) [@TheMadHun](https://boards.straightdope.com/u/TheMadHun)\ **Post date:** [September 1, 2009, 8:00pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/24 "2009-09-01T20:00:03Z")
My current ticket is for 25 mph in a school zone, the state norm. As to who agrees to these things, it’s usually a few trend setting states and then the others agree to a Uniform Code without much discussion. ---
**Author:** ![asterion](https://avatars.discourse-cdn.com/v4/letter/a/4da419/32.png) [@asterion](https://boards.straightdope.com/u/asterion)\ **Post date:** [September 1, 2009, 8:12pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/25 "2009-09-01T20:12:17Z")
> [@elmwood](#): > > The answers are the typical “the exception is the norm” responses one might expect. > > Anyhow, New Mexico is somewhat well-known for a statewide and VERY strictly enforced 15 MPH school zone speed limit. Drive 17 or 18 through an active school zone in Las Cruces, Albuquerque or anywhere else in the state, and odds are very good you’ll end up with an expensive ticket. Did the Legislature put a state-wide change through in the last session? Throughout the 1990s in Albuquerque the speed limit was 15 for elementary schools, 20 for middle schools, and 25 for high schools. I wasn’t looking for school zone signs last November, but I don’t remember that changing. ---
**Author:** ![Ad\_Astra](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Ad\_Astra](https://boards.straightdope.com/u/Ad_Astra)\ **Post date:** [September 2, 2009, 1:36am UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/26 "2009-09-02T01:36:39Z")
If you want really weird, then on Washburn University’s campus in Topeka, Kansas, there’s more than a handful of signs with a 12 mph limit. Not 10, not 15, but 12. Why that’s any safer/more efficient/better in any way is beyond me. ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [September 2, 2009, 2:28am UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/27 "2009-09-02T02:28:58Z")
> [@Harmonious\_Discord](#): > > Nobody has come up with a reason that speeds have had any reason for being what they are so far. **I’d like an example for any state that shows how they picked a speed.** I’m very good at speculating myself.🙂 Happy? [http://www.nyc.gov/html/dot/downloads/pdf/Reduced\_School\_Speed\_Limit\_Study.pdf](http://www.nyc.gov/html/dot/downloads/pdf/Reduced_School_Speed_Limit_Study.pdf) ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [September 2, 2009, 5:34am UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/28 "2009-09-02T05:34:48Z")
> [@Ad\_Astra](#): > > If you want really weird, then on Washburn University’s campus in Topeka, Kansas, there’s more than a handful of signs with a 12 mph limit. Not 10, not 15, but 12. Why that’s any safer/more efficient/better in any way is beyond me. I think it has to do with being unusual and therefore perhaps more memorable. When riding the tram at Disneyland (I go a lot) the P.A. spiel has all the info that just runs by your consciousness: “Keep your arms … to thank you for visiting … park closes at … The speed limit in the parking structure is 14 MPH …” What? Did I hear that right? Weird. Why 14 and not, I dunno… It certainly works to break your lack of attention! ---
**Author:** ![Disgruntled\_Penguin](https://avatars.discourse-cdn.com/v4/letter/d/a8b319/32.png) [@Disgruntled\_Penguin](https://boards.straightdope.com/u/Disgruntled_Penguin)\ **Post date:** [September 2, 2009, 5:47am UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/29 "2009-09-02T05:47:37Z")
> [@SmackFu](#): > > In New York, the rule is: > Also, in general, this is the kind of stuff that traffic engineers love to figure out. The idea that they pull a number out of a hat is a bit silly. So, where’d they pull the 85th percentile number from? ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [September 2, 2009, 12:47pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/30 "2009-09-02T12:47:43Z")
> [@SmackFu](#): > > Happy? > [http://www.nyc.gov/html/dot/downloads/pdf/Reduced\_School\_Speed\_Limit\_Study.pdf](http://www.nyc.gov/html/dot/downloads/pdf/Reduced_School_Speed_Limit_Study.pdf) That doesn’t show why they picked a speed. It shows that they are studying ways to make people slow to the selected speed. ---
**Author:** ![Umbriel2](https://avatars.discourse-cdn.com/v4/letter/u/4af34b/32.png) [@Umbriel2](https://boards.straightdope.com/u/Umbriel2)\ **Post date:** [September 2, 2009, 1:06pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/31 "2009-09-02T13:06:38Z")
Along the lines of the OP – does anyone know the reasoning behind having a separate, trivially lower, highway speed limit for trucks? I’ve seen “Trucks 60” signs on some eastern US highways under “Speed Limit 65” signs. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [September 2, 2009, 1:08pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/32 "2009-09-02T13:08:42Z")
> [@Umbriel2](#): > > Along the lines of the OP – does anyone know the reasoning behind having a separate, trivially lower, highway speed limit for trucks? I’ve seen “Trucks 60” signs on some eastern US highways under “Speed Limit 65” signs. It reduces the damage to the road. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [September 2, 2009, 8:21pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/33 "2009-09-02T20:21:07Z")
Just about every speed limit I’ve seen is 20, sparing a few I’ve seen in college areas where it was 25 or 30 I believe. Now, why they needed a school zone at a college is bewildering to me. You’d think by then they would know how to look both ways before crossing a street… ---
**Author:** ![Disgruntled\_Penguin](https://avatars.discourse-cdn.com/v4/letter/d/a8b319/32.png) [@Disgruntled\_Penguin](https://boards.straightdope.com/u/Disgruntled_Penguin)\ **Post date:** [September 2, 2009, 11:53pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/34 "2009-09-02T23:53:59Z")
> [@BrandonR](#): > > Just about every speed limit I’ve seen is 20, sparing a few I’ve seen in college areas where it was 25 or 30 I believe. Now, why they needed a school zone at a college is bewildering to me. You’d think by then they would know how to look both ways before crossing a street… I’d think it would be to give you time to avoid the college students already in the road rather than to keep the students from crossing if they see you first. ---
**Author:** ![TBG](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@TBG](https://boards.straightdope.com/u/TBG)\ **Post date:** [September 3, 2009, 4:25am UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/35 "2009-09-03T04:25:29Z")
> [@Markxxx](#): > > Did you ever try to drive at 10mph? It’s do-able but hard. Yeah, you have to ride the brake pretty much. Not to mention, some cars’ speedometers don’t even start until 15mph. The only places I’ve personally seen any limits less than 15\* are private drives, without real force of law behind them, so I just (with all due caution) treat anything lower as 15. No, I will not observe your silly 4 or 9 mph limits, dumbass neighborhood associations. \*-my statement does NOT include yellow signage about dangerous curves or road conditions or whatnot with a suggested safe speed included, just actual white speed limit signs ---
**Author:** ![Umbriel2](https://avatars.discourse-cdn.com/v4/letter/u/4af34b/32.png) [@Umbriel2](https://boards.straightdope.com/u/Umbriel2)\ **Post date:** [September 3, 2009, 2:01pm UTC](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475/36 "2009-09-03T14:01:00Z")
> [@Harmonious\_Discord](#): > > It reduces the damage to the road. A _5 MPH_ difference reduces damage to the road? Maybe there’s some traffic planner’s formula that produces a savings figure, but it still seems weird to me. Why not 10 or 15 MPH for even greater savings? I was thinking it might have something to do with discouraging trucks from passing, but I’d appreciate any other insights. [Previous page](https://boards.straightdope.com/t/why-15-mph-and-not-10-mph-or-20-mph-in-school-zones-usa/508475.md?page=1)