Speed limit - where does it change?

Hi all,

I’ve been wondering this for awhile now. If, on one stretch of road, the speed limit changes several times (as it does on a road I drive down often - from 35 to 30 to 25), where exactly do you need to comply to the posted limit? e.g., at what point do you obey the upcoming speed limit sign instead of the previous?

Does it change right at the sign? At the midpoint between the signs? etc? Is there some sort of rule of thumb here?


No cite, and it may be different from jurisdiction to jurisdiction, but I’ve been told that the new speed limit takes effect at the sign. Someone with a more authoritative answer and a cite will be along in just a few minutes.

Welcome to the SDMB!

Whether or not this is true, I’d imagine that in court you could argue that the speed limit changes (when going UP) as soon as you can see the sign (what if you turned onto that road in between signs, how would you know). But (I know this is a double standard, that’s why I say you could argue this) it changes (when going DOWN) and the plane orthogonal to the edge of the road way and intersecting the sign post.

The road has a speed limit. It is signed to indicate that. The speed limit applies whether or not you’ve seen a sign.

Judge in the courtroom I work in did not buy the “I can see the sign so that’s the speed limit” defense. His ruling was in Minnesota, it begins at the sign posting the new limit.

Like any other kind of regulation, speed limits are only valid if they meet certain formal criteria. Among other things, they need to be made public in a strictly defined way. In case of speed limits, this includes (and may not be limited to) the sign: no sign, no speed limit. Even if there is a sign, but you had no chance to see it, the limit does not apply. This, of course, may be a matter of what can be proven. How do you prove that a large van had obstructed the sign after the van has moved?
However, in the simple case where there is a clearly visible sign, the speed limit (or whatever the sign says) normally starts where the sign is (in several jurisdictions where I have already driven a car and got myself informed before doing so).

In the UK, it works like this. If you are going from a low speed to a high speed, then you cannot speed up until you reach the sign, i.e. the speed limit applies at points past the sign, but not at the sign

If you are going from high speed to low speed, then you must be driving at the lower speed by the time you reach the sign, i.e. the speed limit applies at the sign.

Hope that’s helpful.

In California, at least, this isn’t true - if no speed limit signs are posted, the speed limit is 25 mph by default.

I got a ticket once when I was “speeding up” between a 35-mph sign and a 55-mph sign about a quarter-mile away. (Sucked because it’s in a zone where you’re heading OUT of a very small burg on a very rural road, and there’s absolutely nothing to justify 35 heading out – but there’s a farm crossing just inside the 35 zone and that’s why the limit applies there. I didn’t fight it because there are plenty of times when I do deserve a ticket but don’t get one.)

You are right, of course. There is a default speed limit nearly everywhere (the only exception I know is the German Autobahn). Thanks for pointing out that inaccuracy in my post.
I was referring only to speed limits apart from those default limits, but I should have made that clear.

In Florida the speed limit applies as soon as the sign is passed; ie. you must have slowed down sufficiently by the time you pass it, and you may not increase speed until you have passed it.

Does that apply outside of city limits, too? Especially in a state the size of California, you’d think there’d be a separate rural implied speed limit. We have one here in Michigan, anyway, and a lot of rural roads with no marked limit. The implied limit is 55mph. Actually, it’s not even implied by explicit, being state law and all.

I’ll admit, though, that it may be higher than 55 – I don’t know what happened when the feds got their noses out of state business, and it’s not important enough for me to look up.

Two tidbits: yellow speed limit signs like on freeway entrance ramps are not regulatory and you may not be ticketed for them.

Also, non-paved roads may not be posted for speed, at least in my state. They default to 55 mph.

BobLibDem -
Whos going to go 55 on a non-paved road? Thatd be nuts!
I dont know about the yellow warning signs not being regulatory. Are you only refering to onramps? Try speeding through a school zone that has a yellow "15 MPH when children are present" sign posted. I think the Yellow part is warning you that if you are speeding it is ***really*** unsafe to so here. I couldnt find a site to back up you or me, however.

True you would be nuts if you drove 55 mph on unpaved roads. But for some reason, our statutes don’t allow for posting them for speed.

By definition, if it’s on yellow background it is advisory only. I think if you got ticketed for violating a yellow sign attached to a white speed limit sign you could fight it. Only black on white signs or stop or yield signs are regulatory. It used to be you’d see white on black signs at RR crossings saying stop when flashing or whatever- those were unenforceable and have virtually all been replaced by black on white.

According to a cop teacher of mine, the limit changes at the sign, and that’s what you’re supposed to drive as soon as you hit the sign. How you get from 65mph to 35mph instantaneously is your problem.

I drove through a section of highway in semi-rural Quebec (Highway 20, I think, outside Dorion) where it was necessary to break the law. The speed limit went from 90 km/h maximum, 70 km/h minimum to 50 km/h maximum, 30 km/h minimum (if I remember correctly). So you either had to drive too slow on the 90 km/h section or too fast on the 50 km/h section.

I should note that this is, by far, one of the least insane aspects of the Quebec highway system.

Here’s the law. It’s confusing.

Here’s how my dad (who’s a retired County Engineer) explained the yellow speed signs to me:

When you see the yellow speed signs under curve signs, that’s the maximum rated safe speed for that particular stretch. IOW, when you see a curve sign with a “45mph” sign directly under it, you’ll be able to safely make the curve under normal driving conditions as long as you are going 45 mph or less. Sure you can take it faster, but at your own risk. They’re not enforcable legally, but posted there as a warning to drivers.

Try this experiment sometime: find one of these curves, go around it at the recommended speed. Then go around it again slightly faster (5 mph faster should be plenty). You’ll notice that ‘seat-of-the-pants’ feeling, where your body seems to lean towards the outer edge of the curve. That’s the sign that you’re taking the curve too fast to be safe.

Similar signs are posted near freeway offramps for the same reasons; if they weren’t there, how many drivers wouldn’t slow down and would go off the road trying to take a 25 mph curve at 60?

I actually had this job once, putting up speed limit & other signs for the State of Texas. Answer the OP…at the sign. Think about school zones and you’ll know.

Also, most unpaved (ie:asphalt/black top) roads here used to default at 70…obviously that didn’t work. So, they knocked it down to 50. Which is in some cases not too fast. Most are now at 40 mph. of course many folks still do 70. Had a kid flip endover 3 times in front of my house this summer. No-one hurt, first words, “I was only doing 50 officer, I swear.” :rolleyes: yeah, okay.