Except as otherwise provided in this section, this part regulates the erection and maintenance of an outdoor sign along or near a federal-aid primary highway, only if: The sign is wholly or partly visible from the main traveled way of the highway; and The sign is: 660 feet or less from the nearest edge of the right-of-way of the highway; or More than 660 feet from the nearest edge of the right-of-way of the highway, and intended to be read from the main traveled way of the highway. Except as provided in §§ 8-734 and 8-735 of this subtitle as to the removal of nonconforming signs, this part does not apply to: An outdoor sign that is 660 feet or less from the nearest edge of a federal-aid primary highway, if the sign was erected on or before July 1, 1968; or An outdoor sign that is more than 660 feet from the nearest edge of a federal-aid primary highway, if the sign was erected on or before July 1, 1975. This part does not apply to on premise outdoor signs.