(a) 23 U.S.C. 131 provides that signs adjacent to the Interstate and Federal-aid Primary Systems which are visible from the main-traveled way and within 660 feet of the nearest edge of the right-of-way, and those additional signs beyond 660 feet outside of urban areas which are visible from the main-traveled way and erected with the purpose of their message being read from such main-traveled way, shall be limited to the following:

(1) Directional and official signs and notice which shall conform to national standards promulgated by the Secretary in subpart B, part 750, chapter I, 23 CFR, National Standards for Directional and Official Signs;

(2) Signs advertising the sale or lease of property upon which they are located;

(3) Signs advertising activities conducted on the property on which they are located;

(4) Signs within 660 feet of the nearest edge of the right-of-way within areas adjacent to the Interstate and Federal-aid Primary Systems which are zoned industrial or commercial under the authority of State law;

(5) Signs within 660 feet of the nearest edge of the right-of-way within areas adjacent to the Interstate and Federal-aid Primary Systems which are unzoned commercial or industrial areas, which areas are determined by agreement between the State and the Secretary; and

(6) Signs lawfully in existence on October 22, 1965, which are determined to be landmark signs.

(b) 23 U.S.C. 131(d) provides that signs in § 750.704(a) (4) and (5) must comply with size, lighting, and spacing requirements, to be determined by agreement between the State and the Secretary.

(c) 23 U.S.C. 131 does not permit signs to be located within zoned or unzoned commercial or industrial areas beyond 660 feet of the right-of-way adjacent to the Interstate or Federal-aid Primary System, outside of urban areas.

(d) 23 U.S.C. 131 provides that signs not permitted under § 750.704 of this regulation must be removed by the State.