# What is (are) the Minimum Speed on the USA Interstate Highway System?
**URL:** https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683
**Category:** Factual Questions
**Created:** [August 22, 2016, 11:02pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683 "2016-08-22T23:02:01Z")
**Posts on this page:** 6
**Page:** 2
### Author:  [@bump](https://boards.straightdope.com/u/bump)
#### Post date: [August 23, 2016, 3:26pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/21 "2016-08-23T15:26:11Z")
> [@thelurkinghorror](#):
>
> I specifically remembered Florida because of old people stereotypes.
>
> The maximium speed limit also [varies by state](https://en.wikipedia.org/wiki/Speed_limit#/media/File:World_Speed_Limits.svg), to a high of 85 in Texas. This is after more than two decades of strict Federal restrictions on speed limits that states now set their own limits. Montana is also very “nudge, nudge, wink, wink” about not enforcing speed limits in some areas.
ISTR (it’s been 28 years since driver’s ed) that on Texas highways, including interstates, the minimum speed limit is 15 MPH under the posted maximum speed limit. So if the max is 75 mph, the min is 60 mph.
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### Author:  [@Common\_Tater](https://boards.straightdope.com/u/Common_Tater)
#### Post date: [August 23, 2016, 3:29pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/22 "2016-08-23T15:29:03Z")
> [@kenobi\_65](#):
>
> There are hills in Iowa? 😉
In the northeast part, yes. There is even, and I’m not making this up, \*a runaway truck ramp!\*LOL
[http://www.iowahighwayends.net/roadtrips/lacrosse/lacrosse.html](http://www.iowahighwayends.net/roadtrips/lacrosse/lacrosse.html)
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### Author:  [@Kimballkid](https://boards.straightdope.com/u/Kimballkid)
#### Post date: [August 23, 2016, 3:42pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/23 "2016-08-23T15:42:35Z")
In South Dakota, the minimum is 40 MPH. You’ll see it occasionally on a little sign attached to a speed limit sign but not on all speed limit signs.
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### Author:  [@Pai325](https://boards.straightdope.com/u/Pai325)
#### Post date: [August 23, 2016, 3:49pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/24 "2016-08-23T15:49:01Z")
They had them in Illinois. Many of times I was stopped in traffic right next to the “Minimum Speed 45 mph” sign.
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### Author:  [@DrDeth](https://boards.straightdope.com/u/DrDeth)
#### Post date: [August 23, 2016, 5:16pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/25 "2016-08-23T17:16:43Z")
> [@thelurkinghorror](#):
>
> As noted, California is at discretion, and I think it would be very difficult to enforce any arbitrary speed on e.g. I-80 through the Sierras, where semi truck (and sometimes passenger vehicle) speed is limited by the uphill grade.
IN CA, the law in mostly enforced if you’re driving crazy slow outside the "slow’ lane, and traffic is zooming past on both sides. Or if many vehicles are backed up behind you and you dont take turnouts.
So, to put it another way, if the posted limit is 55 on a country highway, and there’s a radar speed trap: If you’re going too fast they will tag you, despite traffic. If you’re going too slow they will only tag you if you have become a hazard.
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### Author:  [@joe.russell](https://boards.straightdope.com/u/joe.russell)
#### Post date: [August 23, 2016, 5:23pm UTC](https://boards.straightdope.com/t/what-is-are-the-minimum-speed-on-the-usa-interstate-highway-system/763683/26 "2016-08-23T17:23:17Z")
> [@Common\_Tater](#):
>
> In the northeast part, yes. There is even, and I’m not making this up, \*a runaway truck ramp!\*LOL
>
> [La Crosse road trip](http://www.iowahighwayends.net/roadtrips/lacrosse/lacrosse.html)
Yes! Relatively flat compared to most states, but the closer u get to Wisconsin and the Mississippi river it gets pretty drastic. Enough to pop my ears a few times!
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