One time, on a long, straight, downhill on-ramp to an interstate highway, there was a cop pointing his laser at the cars that were going down the ramp on their way to enter the highway. The speed limit on the highway is 65 mph, while the speed limit on the street that the other end of the ramp is connected to is 35 mph, but no speed is posted on the ramp, however, and the cop seemed to be trying to take advantage of that ambiguity, perhaps trying to punish people for reaching the highway's speed limit too early. So what exactly would the speed limit be on such a ramp?
Typically - in fact - in almost all cases - there are no posted, regulatory speed limits for on- and off- ramps.
This article proved interesting. Specifically,
Those ramp speed signs, black numerals on a yellow field, are advisory only. They have no force of law. The only regulatory speed signs are the black-on-white speed limits posted on the roadway itself.
In other words, if you take a ramp on two wheels, a police officer can ticket you for reckless driving, but if a ramp is posted at 35 mph and you take it at 45 without creating a danger to yourself or others, you can't be ticketed for speeding.
The first signs referred to are signs for the advisory speed limit. They look like this:
From Wikipedia, listed as an example for highway ramps.
. . .
"Why don't they just post those speeds on black-and-white signs, I wonder? Then there would be no doubt."
We wondered, too, so we asked the DOT that very question.
And the answer was, they do it because that's the way it's done all over the country, and the reason it's done all over the country is that ramps are generally considered too short a distance over which to enforce a speed limit.