This subdivision shall govern the designation of scenic or historic rights-of-way
or districts within the city limits.
(b)
This subdivision shall not apply to signs lawfully erected and lawfully existing on
April 14, 1983, that are on the federal aid primary system and subject to regulation
under the Texas Litter Abatement Act, V.T.C.A., Transportation Code § 391.001 et seq.,
including all amendments (the state act), or that are subject to regulation under
the Federal Highway Beautification Act, 23 USC 131 et seq., including all amendments
(the federal act).