“School bus” means a motor vehicle that is described by any of the following:
A vehicle that is marked with or displays the words “school bus.”
A vehicle that is used to transport students to or from school and may be used to transport students to or from authorized school activities or functions and that is not a vehicle described by any of the following:
A vehicle subject to regulation under ORS chapter 825.
A vehicle, commonly known as a private passenger car or private passenger van, that is used by the owner of the vehicle or a relative of the owner of the vehicle for personal transportation of students to or from school or school activities and is not used for compensation except for the sharing of expenses in a ridesharing arrangement or reimbursement of mileage.