(a) In section 131 of title 23 U.S.C., Congress has declared that:

(1) The erection and maintenance of outdoor advertising signs, displays, and devices in areas adjacent to the Interstate System and the primary system should be controlled in order to protect the public investment in such highways, to promote safety and recreational value of public travel, and to preserve natural beauty.

(2) Directional and official signs and notices, which signs and notices shall include, but not be limited to, signs and notices pertaining to natural wonders, scenic and historical attractions, which are required or authorized by law, shall conform to national standards authorized to be promulgated by the Secretary, which standards shall contain provisions concerning the lighting, size, number and spacing of signs, and such other requirements as may be appropriate to implement the section.

(b) The standards in this part are issued as provided in section 131 of title 23 U.S.C.