Washington Revised Code Title 46. Motor Vehicles § 46.37.400. Mirrors, backup devices

(1) Every motor vehicle shall be equipped with a mirror mounted on the left side of the vehicle and so located to reflect to the driver a view of the highway for a distance of at least two hundred feet to the rear of such vehicle.

(2) Every motor vehicle shall be equipped with an additional mirror mounted either inside the vehicle approximately in the center or outside the vehicle on the right side and so located as to reflect to the driver a view of the highway for a distance of at least two hundred feet to the rear of such vehicle.

(3) Every truck registered or based in Washington that is equipped with a cube-style, walk-in cargo box up to eighteen feet long used in the commercial delivery of goods and services must be equipped with a rear crossview mirror or backup device to alert the driver that a person or object is behind the truck.

(4) All mirrors and backup devices required by this section shall be maintained in good condition. Rear crossview mirrors and backup devices will be of a type approved by the Washington state patrol.