(a) Route 111 is from:
(1) The international border south of Calexico to Route 78 near Brawley, passing east of Heber.
(2) Route 78 near Brawley to Route 86 via the north shore of the Salton Sea.
(3) The western city limits of Cathedral City to Route 10 near Whitewater.
(b) The relinquished former portions of Route 111 within the Cities of Cathedral City, Indian Wells, Indio, La Quinta, Palm Desert, and Rancho Mirage are not state highways and are not eligible for adoption under Section 81. The Cities of Indian Wells, Indio, La Quinta, and Palm Desert, as applicable, shall maintain within their respective jurisdictions signs directing motorists to the continuation of Route 111.