Pursuant to RCW 46.61.165 and 47.52.025, the department has reserved portions of interstate highways, state highways, and ramps, as HOV lanes for the exclusive use of public transportation vehicles or private motor vehicles with the number of occupants specified on signs. Motor vehicles authorized to use HOV lanes are:

(1) Rubber tired municipal transit vehicles conforming to RCW 46.04.355.

(2) Buses with a carrying capacity of sixteen or more persons, including the operator.

(3) Motorcycles conforming to RCW 46.04.330.

(4) Recreational vehicles with the number of occupants specified on signs.

(5) Official marked law enforcement and fire department vehicles equipped with emergency lights and siren, operated by an on-duty state patrol, local, or county law enforcement personnel, or on-duty local, county, or special district fire department personnel.

(6) All other vehicles with the number of occupants specified on signs, except that trucks in excess of 10,000 lb. G.V.W. are prohibited from the use of HOV lanes regardless of the number of occupants. Tow trucks that would be otherwise prohibited because of weight or number of occupants may use HOV lanes when en route to an emergency on a specific roadway or roadside.