(a) Route 92 is from:
(1) Route 1 near Half Moon Bay to Route 280.
(2) Route 280 to Route 580 near Castro Valley and Hayward.
(b) The relinquished former portion of Route 92 within the City of Hayward is not a state highway and is not eligible for adoption under Section 81. For the relinquished former portion of Route 92, the City of Hayward shall maintain within its jurisdiction signs directing motorists to the continuation of Route 92 or to the state highway system, as applicable, and shall ensure the continuity of traffic flow on the relinquished portion of Route 92, including any traffic signal progression.