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.

(1) RCW 46.61.100(3) mandates that no vehicle towing a trailer or no vehicle or combination over 10,000 lb. may use the left lane of limited access roadways having three or more lanes in one direction, and that a high occupancy vehicle (HOV) lane is not considered the left hand lane of a roadway. Within this section, 10,000 lb. means 10,000 lb. gross vehicle weight (G.V.W.).

(2) RCW 46.61.100(3) further mandates that the department, in consultation with the Washington state patrol, shall adopt rules specifying those circumstances where it is permissible for other vehicles to use the left lane in case of emergency or to facilitate the orderly flow of traffic, and those segments of limited access highways exempt from the subsection due to the operational characteristics of the roadway.

(a) For the types of vehicles specified, and under the circumstances enumerated in (a)(i) through (vii) of this subsection, the left lane prohibition described in subsection (1) of this section does not apply to:

(i) Motorcycles towing trailers.

(ii) Class B motor homes, commonly called conversion vans, without a motor vehicle or trailer in tow.

(iii) Tow trucks weighing over 10,000 lb. G.V.W. when en route to an emergency on a specific roadway or roadside.

(iv) Fire trucks or emergency care vehicles weighing over 10,000 lb. G.V.W. when en route to an emergency.

(v) Any vehicle towing a trailer or vehicle or combination weighing over 10,000 lb. G.V.W. when one or more of the lanes are blocked because of an accident, other incident, or highway maintenance or construction activities.

(vi) Any vehicle authorized to use a HOV lane that would otherwise be prohibited from the left lane within two miles approaching the beginning of a HOV lane or following the terminus of a HOV lane.

(vii) Any department of transportation vehicle towing a trailer or weighing over 10,000 lb. G.V.W. when conducting official business within the left lane.

(b) On the roadway portions enumerated in (b)(i) through (viii) of this subsection, the left lane prohibition described in subsection (1) of this section does not apply:

(i) On northbound and southbound Interstate 5 in the Vancouver vicinity, from the Washington/Oregon state line to exit 3 at Main Street.

(ii) On northbound Interstate 5 in the Vancouver vicinity, from the confluence of Interstate 205 to exit 9 at 179th Street.

(iii) On southbound Interstate 5 in the Vancouver vicinity, from exit 9 at 179th Street to exit 7 at Interstate 205.

(iv) On northbound Interstate 5 in the Seattle/Everett vicinity, from exit 154A at I-405 to exit 194 at SR 529.

(v) On southbound Interstate 5 in the Seattle/Everett vicinity, from exit 189 at SR 526 to exit 154A at I-405.

(vi) On eastbound and westbound Interstate 90 in the Seattle vicinity, from exit 2A and 2B respectively at Interstate 5 to exit 10A at Interstate 405.

(vii) On eastbound and westbound Interstate 182 in the Tri-cities vicinity, from exit 4 to exit 12A.

(viii) On northbound and southbound Interstate 205 in the Vancouver vicinity, from the Washington/Oregon state line to the termini of the three lane sections about one-half mile south of exit 32.

(c) On the roadway portions enumerated in (c)(i) and (ii) of this subsection, the left lane prohibition described in subsection (1) of this section does not apply to any vehicle, except trucks over 10,000 lb. G.V.W., when using the left lane for passing to facilitate the orderly flow of traffic:

(i) On southbound Interstate 5 in the Southcenter vicinity, from exit 154A at I-405 to exit 151 at South 200th Street.

(ii) On southbound Interstate 5 in the Tacoma vicinity, from exit 135 at SR 167 to exit 130 at South 56th Street.