This subpart prescribes the Federal Highway Administration (FHWA) policies and requirements relating to the effective control of outdoor advertising under 23 U.S.C. § 131. The purpose of these policies and requirements is to assure that there is effective State control of outdoor advertising in areas adjacent to Interstate and Federal-aid primary highways. Nothing in this subpart shall be construed to prevent a State from establishing more stringent outdoor advertising control requirements along Interstate and Primary Systems than provided herein.