Washington Revised Code Title 4. Civil Procedure § 4.24.770. Private employer not liable for injury to unauthorized third-party occupant of private employer’s vehicle

(1) A private employer is not liable for any injury received by a third-party occupant of a vehicle that is owned, leased, or rented by the employer if, at the time the injuries were inflicted, the third-party occupant was riding in or on the vehicle with an employee who had explicitly acknowledged in writing the employer's policy on use of vehicles owned, leased, or rented by the employer and the third-party occupant was not:

(2) For purposes of this section, “third-party occupant” means a person who occupies a vehicle owned, leased, or rented by the private employer and who is not an officer, employee, or agent, or authorized or constructive invitee of the private employer.