Oregon Revised Statutes Oregon Vehicle Code § 815.140

(1) A person commits the offense of failure to use vehicle traction tires or chains if the person drives or moves or owns and causes or knowingly permits to be driven or moved any motor vehicle or trailer on any highway if the highway is posted showing conditions that require vehicle traction tires or chains and the vehicle is not equipped with vehicle traction tires or chains that are required for the posted conditions.

(2) Traction tires or chains that are referred to in this section are those established by rule under the authority granted under ORS 815.045.

(3) This section does not apply to vehicles exempted from this section under ORS 815.145.

(4) This section only applies to sections of highway on which a road authority requires the use of traction tires or chains and on which signs requiring the use of traction tires or chains have been posted as provided in ORS 815.045.

(5) A court shall not find a person to be in violation of the offense described under this section if the court determines that the conditions of the highway at the time the person was cited did not require posting under rules adopted under ORS 815.045. The defense under this subsection may be affirmatively asserted by any person cited for violation of the offense described in this section.

(6) The offense described in this section, failure to use vehicle traction tires or chains, is a Class C traffic violation.