N.C. Gen. Stat. § 136-33.2A: Signs marking beginning of reduced speed zones.

If a need to reduce speed in a speed zone is determined to exist by an engineer of the Department, there shall be a sign erected, of adequate size, at least 600 feet in advance of the beginning of any speed zone established by any agency of the State authorized to establish the same, which shall indicate a change in the speed limit. (2007-164, s. 3.)