(a) Route 164 is Rosemead Boulevard from:
(1) Gallatin Road near Pico Rivera to the southern city limit of Temple City in the vicinity of Grand Avenue.
(2) Route 210 to Foothill Boulevard in the City of Pasadena.
(b) The relinquished former portions of Route 164 within the County of Los Angeles and the City of Temple City are not state highways and are not eligible for adoption under Section 81. For the relinquished former portions of Route 164, the County of Los Angeles and the City of Temple City shall maintain within their respective jurisdictions signs directing motorists to the continuation of Route 164.