Policies for erecting road signs

I spent the last few days driving on various highways across America and this gave me time to contemplate. But given the setting, most of my contemplation was directed towards road conditions.

Is there some policy about where road signs are erected? Specifically, speed limit signs. Let’s say you start driving on a road and want to know what the speed limit is. How long should you expect to have to drive before seeing a speed limit sign?

Start here:

[li]Manual on Uniform Traffic Control Devices[/li][/ul]

There should be a speed limit sign after every entry point on that road, especially if the limits on each road are different. If there are several crossroads near each other, after the last one. This is not as important in cities where nearly all the streets are the same speed limit.


There is a reason every city and state has statutory speed limits. If there isn’t a speed limit sign, you go the statutory limit. The problem is these limits can vary widely and most folks don’t have any idea what they are. When you cross the border in the city I live, you are greeted with a sign that welcomes you and another sign that says speed limit 25 unless otherwise posted. That is the statutory limit.

Not every speed limit sign is an enforceable speed limit. In order to be enforceable, the sign must be white with black letters, between X and Y feet high (I forgot the exact numbers, maybe 5 and 8 feet. A yellow sign is not enforceable, it is cautionary, such as the ones on curve warnings.

When a speed limit sign says “Speed Limit xx Except Where Posted”, what exactly does that mean? How far do you have to travel before the “not posted” speed limit kicks in?

An extreme example of this was on a multi-lane divided highway I was driving on in Missouri a few years ago. There was a standard speed limit sign that set the speed limit at 60. Then right below it was a sign that said “Speed Limit 25 Except Where Posted”. And every speed limit sign along the highway was like this. I never could figure out what the point of that was. At what point would the speed limit on this highway default to 25 mph?

Could it provide evidence for a “going too fast for conditions”?

Yes, but that is not the same offense as “speeding”, and can be applied whether or not it is signposted. The signs can come into play as evidence, when an accident occurs where blame can be assigned to exceeding the recommended speed. The mere fact that a driver, under ordinary circumstances, exceeds the cautionary speed and does not lose conrol is not of itself a ticketable offense. Exceeding a black and white speed limit sign is.

By the way, I asked cops about this, and the general consensus is that the speed limit is in place at a spot where the speed limit sign is clearly visible to the driver. In other words, you must begin reducing your speed as soon as you can read the speed limit sigh, or can begin to accelerae as soon as you can see a higher speed limit sigh.

On some highways around here they’ve put up electronic speed limit signs so the speed limit can be set to match traffic conditions. Since those are much costlier than metal signs, you can drive by several on ramps without seeing one.

Doubling the issue is that even if you drive that stretch of road regularly, you may have no idea what the current speed limit is until you have driven for quite a few miles on it.

That might be possible on a limited access highway. But what happens on a regular highway? It might have a dozen of intersections in a relatively short stretch of road.

In my dense suburban area the major arterials form a 1 mile grid. Speed limits on these are 45mph. Except where they’re 40 or 35. You can easily go a mile or two without seeing a speed limit sign. That’s easily a dozen cross streets. Not to mention umpteen dozen commercial driveways.

It is real common to have no idea what the limit is until a sign finally hoves into view a mile after you join the arterial.

The good news is everybody drives 60 or better, so if you’re doing only 50 you’re pretty safe from ticketing. Though not safe from being honked at, middle-fingered, or rear-ended.

It’s all a trade-off I guess. :slight_smile: