RCW 46.61.215: Highway construction and maintenance.

(1) The driver of a vehicle shall yield the right-of-way to any authorized vehicle or pedestrian actually engaged in work upon a highway, including highway construction and highway maintenance workers, and flaggers, within any highway construction or maintenance area indicated by official traffic control devices.

(2) The driver of a vehicle shall yield the right-of-way to any authorized vehicle obviously and actually engaged in work upon a highway whenever such vehicle displays flashing lights meeting the requirements of RCW 46.37.300.