(1) It is unlawful for any public officer having charge of any vehicle owned or controlled by any county, city, town, or public body in this state other than the state of Washington and used in public business to operate the same upon the public highways of this state unless and until there shall be displayed upon such automobile or other motor vehicle in letters of contrasting color not less than one and one-quarter inches in height in a conspicuous place on the right and left sides thereof, the name of such county, city, town, or other public body, together with the name of the department or office upon the business of which the said vehicle is used. This section shall not apply to vehicles of a sheriff's office, local police department, or any vehicles used by local peace officers under public authority for special undercover or confidential investigative purposes. This subsection shall not apply to: (a) Any municipal transit vehicle operated for purposes of providing public mass transportation; (b) any vehicle governed by the requirements of subsection (4) of this section; nor to (c) any motor vehicle on loan to a school district for driver training purposes. It shall be lawful and constitute compliance with the provisions of this section, however, for the governing body of the appropriate county, city, town, or public body other than the state of Washington or its agencies to adopt and use a distinctive insignia which shall be not less than six inches in diameter across its smallest dimension and which shall be displayed conspicuously on the right and left sides of the vehicle. Such insignia shall be in a color or colors contrasting with the vehicle to which applied for maximum visibility. The name of the public body owning or operating the vehicle shall also be included as part of or displayed above such approved insignia in colors contrasting with the vehicle in letters not less than one and one-quarter inches in height. Immediately below the lettering identifying the public entity and agency operating the vehicle or below an approved insignia shall appear the words "for official use only" in letters at least one inch high in a color contrasting with the color of the vehicle. The appropriate governing body may provide by rule or ordinance for marking of passenger motor vehicles as prescribed in subsection (2) of this section or for exceptions to the marking requirements for local governmental agencies for the same purposes and under the same circumstances as permitted for state agencies under subsection (3) of this section.
(2) Except as provided by subsections (3) and (4) of this section, passenger motor vehicles owned or controlled by the state of Washington, and purchased after July 1, 1989, must be plainly and conspicuously marked on the lower left-hand corner of the rear window with the name of the operating agency or institution or the words "state motor pool," as appropriate, the words "state of Washington — for official use only," and the seal of the state of Washington or the appropriate agency or institution insignia, approved by the department of enterprise services. Markings must be on a transparent adhesive material and conform to the standards established by the department of enterprise services. For the purposes of this section, "passenger motor vehicles" means sedans, station wagons, vans, light trucks, or other motor vehicles under ten thousand pounds gross vehicle weight.
(3) Subsection (2) of this section shall not apply to vehicles used by the Washington state patrol for general undercover or confidential investigative purposes. Traffic control vehicles of the Washington state patrol may be exempted from the requirements of subsection (2) of this section at the discretion of the chief of the Washington state patrol. The department of enterprise services shall adopt general rules permitting other exceptions to the requirements of subsection (2) of this section for other vehicles used for law enforcement, confidential public health work, and public assistance fraud or support investigative purposes, for vehicles leased or rented by the state on a casual basis for a period of less than ninety days, and those provided for in RCW
46.08.066. The exceptions in this subsection, subsection (4) of this section, and those provided for in RCW
46.08.066 shall be the only exceptions permitted to the requirements of subsection (2) of this section.
(4) Any motorcycle, vehicle over 10,000 pounds gross vehicle weight, or other vehicle that for structural reasons cannot be marked as required by subsection (1) or (2) of this section that is owned or controlled by the state of Washington or by any county, city, town, or other public body in this state and used for public purposes on the public highways of this state shall be conspicuously marked in letters of a contrasting color with the words "State of Washington" or the name of such county, city, town, or other public body, together with the name of the department or office that owns or controls the vehicle.
(5) All motor vehicle markings required under the terms of this chapter shall be maintained in a legible condition at all times.