Washington Revised Code Title 46. Motor Vehicles § 46.61.120. Limitations on overtaking on the left

No vehicle shall be driven to the left side of the center of the roadway in overtaking and passing other traffic proceeding in the same direction unless authorized by the provisions of RCW 46.61.100 through 46.61.160 and 46.61.212 and unless such left side is clearly visible and is free of oncoming traffic for a sufficient distance ahead to permit such overtaking and passing to be completely made without interfering with the operation of any traffic approaching from the opposite direction or any traffic overtaken.  In every event the overtaking vehicle must return to an authorized lane of travel as soon as practicable and in the event the passing movement involves the use of a lane authorized for vehicles approaching from the opposite direction, before coming within two hundred feet of any approaching traffic.