(a) Each county, municipality, college, and university using speed detection devices shall erect signs on every highway which comprises a part of the state highway system at that point on the highway which intersects the corporate limits of the municipality, the county boundary, or the boundary of the college or university campus. Such signs shall be at least 24 by 30 inches in area and shall warn approaching motorists that speed detection devices are being employed. No such devices shall be used within 500 feet of any such warning sign erected pursuant to this subsection.

(b) In addition to the signs required under subsection (a) of this Code section, each county, municipality, college, and university using speed detection devices shall erect speed limit warning signs on every highway which comprises a part of the state highway system at that point on the highway which intersects the corporate limits of the municipality, the county boundary, or the boundary of the college or university campus. Such signs shall be at least 24 by 30 inches in area, shall warn approaching motorists of changes in the speed limit, shall be visible plainly from every lane of traffic, shall be viewable in any traffic conditions, and shall not be placed in such a manner that the view of such sign is subject to being obstructed by any other vehicle on such highway. No such devices shall be used within 500 feet of any such warning sign erected pursuant to this subsection.

(c) In addition to the signs required under subsections (a) and (b) of this Code section, each law enforcement agency using an automated traffic enforcement safety device as provided for in Code Section 40-14-18 shall erect signs warning of the use of a stationary speed detection device within the approaching school zone. Such signs shall be at least 24 by 30 inches in area, shall be visible plainly from every lane of traffic, shall be viewable in all traffic conditions, and shall not be placed in such a manner that the view of such sign is subject to being obstructed by any other vehicle on such highway. Such signs shall be placed within 500 feet prior to the warning sign announcing the reduction of the speed limit for the school speed zone. There shall be a rebuttable presumption that such signs are properly installed pursuant to this subsection at the time of any alleged violation under this article.