Ray,
Don't you mean is supposed to prohibit them? I haven't seen a posted speed limit, stop sign, or stop light of any kind that stops drivers around here from exceeding the limits. I believe it was Wyoming that used to have a no posted speed limit and it was up to the state police to decide if a person was driving to fast for the conditions. I don't care for that as one may stop you for doing 40 and the next one won't stop you if you are doing 90. And now with the new phones, we no longer have to worry about people talking and running through lights. They will be playing games on the Internet.
Ron