Yes. A speed limit sign is an example of a regulatory sign.
No, you cannot park next to a speed limit sign.
In the UK the speed limit comes into force as soon as you pass the speed limit sign. As such the distance is zero as you should have slowed down to the posted speed limit before passing the sign.
A motorist is expected not to drive faster than the speed limit on the sign until the school has been passed.
It is unknown who invented the speed limit sign. However, the first maximum speed limit was the 10mph (16km/h) limit introduced in theUnited Kingdomin 1861.
When it is flashing the speed posted is the limit
It varies by jurisdiction.
Regulation Sign Example will be the Speed Limit 50
The increased speed limit goes into effect AT the speed limit sign, not at any point before that. While you're not likely to get cited for accelerating at a reasonable point before you actually get to the sign, you're still bound by the prior speed limit until you actually reach that sign.
When the school speed limit sign shows 20 mph flashing, the maximum speed limit is 20 miles per hour.
When there is no speed limit sign posted on a road, it means that drivers should follow the default speed limit set by the law for that type of road.
When another speed limit sign is reached that changes the limit from the previously posted one.