No unauthorized person shall erect or maintain on any highway any warning or direction sign, signal, or light in imitation of any official traffic control device erected as provided by law. No person shall erect or maintain on any highway any traffic control device bearing any commercial advertising. Nothing in this section shall prohibit the erection or maintenance of signs or signals bearing the name of an organization authorized to erect it by the Commonwealth Transportation Board, the Department of Transportation, or local authorities of counties, cities, and towns as provided by law. Nor shall this section be construed to prohibit the erection by contractors or public utility companies of temporary signs approved by the Virginia Department of Transportation warning motorists that work is in progress on or adjacent to the highway. Any violation of this section shall constitute a Class 4 misdemeanor.