In order to promote the reasonable, orderly and effective display of outdoor advertising while remaining consistent with the purposes of this article, signs, displays and devices, whose size, lighting and spacing shall be determined by agreement between the Commissioner of Highways of West Virginia and the Secretary of Transportation of the United States, may be erected and maintained within six hundred sixty feet of the nearest edge of the right-of-way of federal-aid interstate or primary roads, within areas zoned industrial or commercial, or in unzoned commercial or industrial areas, as may be determined by agreement between the Commissioner of Highways of West Virginia and the Secretary of Transportation of the United States: Provided, That any such agreement shall contain a definition of unzoned commercial or industrial areas which reflects existing conditions in this state, such as, without limiting the foregoing, existing land use, availability of land for urban development, topography and accepted zoning practices now prevailing in this state. Any agreement between the Commissioner of Highways and the Secretary of Transportation relating to size, lighting and spacing shall reflect customary usage in this state. Any agreement between the Commissioner of Highways and the Secretary of Transportation defining unzoned commercial or industrial areas, or relating to size, lighting and spacing, shall be no more restrictive than necessary to secure to this state any federal aid contingent upon compliance with federal laws, or federal rules and regulations relating to outdoor advertising, and shall be subject to amendment or rejection by the Legislature of West Virginia: Provided, however, That the terms of any such agreement shall be no more restrictive than those included in any other similar agreement made by the Secretary of Transportation and other states: Provided further, That such agreement shall provide for its modification and amendment in the event and to the extent that the Secretary of Transportation and any other state shall thereafter agree to any provisions which shall be less restrictive. The provisions of this section shall not apply to signs, displays and devices referred to in clauses (b) and (c), section seven of this article.