The term is speed limit. Everyone has a right to go below the speed limit as long as they are going above the speed minimum. You (figurative you) do not have a right go above the speed limit. You do not have a right to expect others to go above the speed limit. When you go above the speed limit, you are breaking the law.

A five mph (eight or ten if you're using kph?) cushion is reasonable because nobody can stay exactly at the speed limit at all times. Speed limits are there for a reason.