Operators of vehicles and pedestrians must follow the instructions of any official traffic control device, unless otherwise directed by a traffic or police officer, subject to exceptions for authorized emergency vehicles.
Except when directed to proceed by an authorized flagger, a police officer, or a firefighter with lawful authority to direct, control, or regulate traffic, every driver of a vehicle approaching a stop sign shall stop at a clearly marked stop line. Except when directed by a flagger, police officer, or firefighter, the driver of a vehicle approaching an intersection controlled by a traffic control signal that is temporarily without power or is not displaying any green, red, or yellow indication to the approach the vehicle is on, shall consider the intersection to be an all-way stop.
When construction, repair, or maintenance work is conducted on or adjacent to a roadway, and when the work interferes with the normal and established mode of travel on the roadway, the location must have properly posted, prominently displayed signs or flaggers, or both.
It is unlawful to willfully fail or refuse to comply with any lawful order or direction of any duly authorized flagger or any police officer or firefighter invested by law with authority to direct, control, or regulate traffic. A violation of this law is a misdemeanor, which is punishable by a maximum term of not more than 90 days or by a fine of not more than $1,000, or by both.
Under Washington State Department of Transportation administrative rule, a single flagger is prohibited from flagging from the center of an intersection, except when there is an emergency or when law enforcement is flagging. When flagging at an intersection, a flagger is required to control each intersection leg.
Flagger directions at signalized intersections may not be in conflict with signal displays and the signal must either be shut down or placed in flash mode as appropriate for the intersection operation except during emergencies.
In cities with a population of 700,000 or greater, a single flagger located in the middle of an intersection may direct traffic without a traffic or police officer present as part of the traffic control plan approved by the city. Operators of vehicles and pedestrians are not required to follow the instructions of official traffic control devices when a single flagger is authorized to direct traffic.