California Code, Vehicle Code - VEH § 25266

Vehicles owned by the state and operated by officers or employees of the state who are actually engaged in aqueduct or levee construction, maintenance, patrol, or inspection, or in stream measurement work, may display flashing amber warning lights to the front, sides and rear when parked on the traveled roadway so as to partially obstruct the free flow of traffic, or when moving at a speed slower than the normal flow of traffic.