23 CFR § 750.709 - On-property or on-premise advertising.
(b) When a sign consists principally of brand name or trade name advertising and the product or service advertised is only incidental to the principal activity, or if it brings rental income to the property owner, it shall be considered the business of outdoor advertising and not an on-property sign.
(c) A sale or lease sign which also advertises any product or service not conducted upon and unrelated to the business or selling or leasing the land on which the sign is located is not an on-property sign.
(d) Signs are exempt from control under 23 U.S.C. 131 if they solely advertise the sale or lease of property on which they are located or advertise activities conducted on the property on which they are located. These signs are subject to regulation (subpart A, part 750, chapter I, 23 CFR) in those States which have executed a bonus agreement, 23 U.S.C. 131(j). State laws or regulations shall contain criteria for determining exemptions. These criteria may include:
(1) A property test for determining whether a sign is located on the same property as the activity or property advertised; and
(2) A purpose test for determining whether a sign has as its sole purpose the identification of the activity located on the property or its products or services, or the sale or lease of the property on which the sign is located.
(3) The criteria must be sufficiently specific to curb attempts to improperly qualify outdoor advertising as “on-property” signs, such as signs on narrow strips of land contiguous to the advertised activity when the purpose is clearly to circumvent 23 U.S.C. 131.
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