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#1
Old 08-22-2016, 07:02 PM
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What is (are) the Minimum Speed on the USA Interstate Highway System?

Is there one minimum speed requirement that applies to all interstate highways in all states, or is the requirement a local one, or is the requirement state-specific? I would think it would be a federally mandated requirement.

I seem to remember 45 MPH as being the min speed, but can't remember where that came from. And that may have been during the double nickle, and may no longer be fast enough.

I am interested in interstate highways only, not US or state divided highway systems, even though in some places the highway systems may coincide. If it's an interstate, I want to know.

So, what is the minimum required speed on interstates?
#2
Old 08-22-2016, 07:48 PM
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There is no federal speed limit, either maximum or minimum -- these limits are set by the States, even on interstate highways.

As far as California is concerned, there is no CA code setting a specific minimum speed limit. However, a person who is driving unreasonably slow may be cited under CA Vehicle Code 2204(a), which provides that:

Quote:
No person shall drive upon a highway at such a slow speed as to impede or block the normal and reasonable movement of traffic unless the reduced speed is necessary for safe operation, because of a grade, or in compliance with law.
#3
Old 08-22-2016, 08:03 PM
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In Missouri (Section 304.001.1)

Quote:
No vehicle shall be operated at a speed of less than forty miles per hour on any highway which is part of the interstate system of highways, unless:

(1) A slower speed is required for the safe operation of the vehicle because of weather or other special conditions; or

(2) Agricultural implements, self-propelled hay-hauling equipment, implements of husbandry and vehicles transporting such vehicles or equipment may be operated occasionally on interstate highways for short distances at a speed of less than forty miles per hour if such vehicle or equipment is operated pursuant to a special permit issued by the chief engineer of the state department of transportation pursuant to section 304.200 and the regulations established pursuant to such section.
#4
Old 08-22-2016, 08:08 PM
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I have only seen posted signs for minimum speed in Florida (I-75 I believe).

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.
#5
Old 08-22-2016, 08:17 PM
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Ohio has a law allowing ODOT to establish a minimum speed limit between 30 and 50 MPH on a controlled-access road, but I don't think this is currently done. In the absence of a sign, the law is just that you can't go "unreasonably slow."

Last edited by Lord Feldon; 08-22-2016 at 08:18 PM.
#6
Old 08-22-2016, 09:07 PM
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Thanks, guys. So, this is quite interesting - the states set the requirement. It's not a federal requirement.

It sounds like there is some discretion allowed. Safety is, of course, first and foremost. Trucks up a steep grade, sure, I can understand not enforcing a (say) 45 MPH minimum speed. If you're loaded and cannot climb the grade faster, then no reasonable infraction should be penalized.

And, e.g., on a California interstate such as I-5 south of Sacramento and going towards Los Angeles (but before the 'Grapevine' - the high mountain passes south of the Central Valley), where in the Central Valley the highway is flat and straight, with very few turns at all and even then they are quite mild, traffic often flows at 80 MPH when the speed limit is 70. The highway is only two lanes, so if a car were going very slowly in the right-most lane, say at 40 MPH, and if there's no legitimate reason to drive so slowly, then you can definitely get a ticket for creating a hazard: the normal flow of traffic in the right lane may have to swerve suddenly to avoid hitting such a slow car.

Last edited by Bullitt; 08-22-2016 at 09:08 PM.
#7
Old 08-22-2016, 09:14 PM
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In Colorado there are sections where a minimum speed is posted.
#8
Old 08-22-2016, 09:20 PM
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I have seen some places where a minimum speed is posted on interstates, but I can't remember what states those were. I'll have to pay closer attention.
#9
Old 08-22-2016, 09:54 PM
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I specifically remembered Florida because of old people stereotypes.

The maximium speed limit also varies by state, 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.
#10
Old 08-22-2016, 10:28 PM
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Quote:
Originally Posted by thelurkinghorror
Montana is also very "nudge, nudge, wink, wink" about not enforcing speed limits in some areas.
They just don't want to let go of "reasonable and prudent."

The idea of a minimum limit is interesting as it could conflict with the basic speed law that says you may not drive faster than what's safe for the current conditions. Driving 45 MPH may not be safe or prudent and thereby unlawful in a heavy rainstorm but if there's a minimum posted speed of 45, what do you do? Violate that minimum or endanger yourself and others?
#11
Old 08-22-2016, 11:17 PM
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Quote:
Originally Posted by gotpasswords View Post
... in a heavy rainstorm but if there's a minimum posted speed of 45, what do you do? Violate that minimum or endanger yourself and others?
Good point. But I think the Basic Speed Law, to never drive faster than the conditions dictate to be safe, always prevails.
#12
Old 08-22-2016, 11:43 PM
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Quote:
Originally Posted by gotpasswords View Post
They just don't want to let go of "reasonable and prudent."

The idea of a minimum limit is interesting as it could conflict with the basic speed law that says you may not drive faster than what's safe for the current conditions. Driving 45 MPH may not be safe or prudent and thereby unlawful in a heavy rainstorm but if there's a minimum posted speed of 45, what do you do? Violate that minimum or endanger yourself and others?
E.g. California: Wet road–go 5 to 10 mph slower.
#13
Old 08-22-2016, 11:49 PM
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Quote:
Originally Posted by gotpasswords View Post
The idea of a minimum limit is interesting as it could conflict with the basic speed law that says you may not drive faster than what's safe for the current conditions.
I'd expect any minimum speed law to be written like the Missouri law posted earlier, which has an exception for when conditions require you to go slower.

Last edited by Lord Feldon; 08-22-2016 at 11:51 PM.
#14
Old 08-23-2016, 12:05 AM
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It's worth noting that nothing about the Interstate System is actually under federal control. Interstates, like "US highways," are owned and operated by the individual states. A nongovernmental body, the American Association of State Highway & Transportation Officials (AASHTO) is the arbiter of whether a highway meets the standards to display an Interstate System sign, and whether the proposed route number is acceptable as part of the interstate numbering scheme.

AASHTO also developed the minimum criteria to be considered part of the Interstate network, though that was formally adopted by the Federal Highway Administration. The 1956 Highway Act offered 90 percent federal funding for interstates, but they were all built by the states.

As for the original question, both minimum and maximum speeds are set by individual states, though the feds did set a nationwide maximum from 1974 until 1995.
#15
Old 08-23-2016, 12:47 AM
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I was taught that it wasn't a fixed speed, just that you can't go more than 25MPH under the speed limit (except due to bad conditions). That type of thing makes more sense to me than a fixed speed. Don't know how true it is, though, even in my state.

Last edited by BigT; 08-23-2016 at 12:47 AM.
#16
Old 08-23-2016, 06:35 AM
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I live in NY state. The maximum on our interstates is 65 mph, and although I've never seen any 'minimum speed' signs I have seen ones on interstates that say 'UNDER 30 MPH MUST USE FLASHERS'. I think it was 30 mph, maybe it was 40.
#17
Old 08-23-2016, 09:06 AM
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Iowa has a law of a min of 45 mph on all interstates. Mostly because of farm equipment I believe. There is also a grade limit on all(?) Interstates of x° where a heavy vehicle should have no problem doing that
#18
Old 08-23-2016, 10:49 AM
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Washington State RCW 46.61.425:

Minimum speed regulation—Passing slow moving vehicle.

(1) No person shall drive a motor vehicle at such a slow speed as to impede the normal and reasonable movement of traffic except when reduced speed is necessary for safe operation or in compliance with law: PROVIDED, That a person following a vehicle driving at less than the legal maximum speed and desiring to pass such vehicle may exceed the speed limit, subject to the provisions of RCW 46.61.120 on highways having only one lane of traffic in each direction, at only such a speed and for only such a distance as is necessary to complete the pass with a reasonable margin of safety.

(2) Whenever the secretary of transportation or local authorities within their respective jurisdictions determine on the basis of an engineering and traffic investigation that slow speeds on any part of a highway unreasonably impede the normal movement of traffic, the secretary or such local authority may determine and declare a minimum speed limit thereat which shall be effective when appropriate signs giving notice thereof are erected. No person shall drive a vehicle slower than such minimum speed limit except when necessary for safe operation or in compliance with law.
#19
Old 08-23-2016, 11:04 AM
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Quote:
Originally Posted by joe.russell View Post
Iowa has a law of a min of 45 mph on all interstates. Mostly because of farm equipment I believe. There is also a grade limit on all(?) Interstates of x° where a heavy vehicle should have no problem doing that
There are hills in Iowa?
#20
Old 08-23-2016, 11:07 AM
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Quote:
Originally Posted by kenobi 65 View Post
There are hills in Iowa?
In Florida, it's the same. But the rest of us call them overpasses.
#21
Old 08-23-2016, 11:26 AM
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Quote:
Originally Posted by thelurkinghorror View Post
I specifically remembered Florida because of old people stereotypes.

The maximium speed limit also varies by state, 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.
#22
Old 08-23-2016, 11:29 AM
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Quote:
Originally Posted by kenobi 65 View Post
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://iowahighwayends.net/roadt.../lacrosse.html
#23
Old 08-23-2016, 11:42 AM
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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.

Last edited by Kimballkid; 08-23-2016 at 11:43 AM.
#24
Old 08-23-2016, 11:49 AM
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They had them in Illinois. Many of times I was stopped in traffic right next to the "Minimum Speed 45 mph" sign.
#25
Old 08-23-2016, 01:16 PM
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Quote:
Originally Posted by thelurkinghorror View Post

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.
#26
Old 08-23-2016, 01:23 PM
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Quote:
Originally Posted by Common Tater View Post
In the northeast part, yes. There is even, and I'm not making this up, a runaway truck ramp!LOL

http://iowahighwayends.net/roadt.../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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