(a) "The Highway" means the John C. Calhoun Memorial Highway.

(b) "Sign" or "outdoor advertising sign" means any outdoor sign, display, device, figure, painting, drawing, message, plaque, poster, billboard, or other thing which is designed, intended or used to advertise or inform, any part of the advertising or informative contents of which is visible from any place on the main-traveled way of the highway.

(c) "Unzoned commercial or industrial area" means the lands occupied by the regularly used buildings, parking lots, storage or processing areas of at least one distinct commercial or industrial activity, and those lands lying along the highway for a distance of seven hundred and fifty feet immediately adjacent to the outermost or end activity. All measurements shall be from the outer edges of the regularly used buildings, parking lots, storage or processing areas of the activities, not from the property line of the activities, and shall be measured parallel to the edge of the highway pavement. An unzoned area, as defined herein, shall not include land predominantly used for residential properties, and land zoned by the State or local law, regulations or ordinance.

(d) "Commercial or industrial activities" means those established activities generally recognized as commercial or industrial by zoning authorities within the area affected by this article, except that none of the following shall be considered commercial or industrial activities:

(1) Outdoor advertising structures.

(2) Agricultural, forestry, ranching, grazing, farming, wayside produce stands and related activities.

(3) Activities conducted in a building principally used as a residence.

(4) Railroad tracks and minor sidings.