Oregon Revised Statutes Oregon Vehicle Code § 814.150

(a) When riding or leading a horse or other livestock on the highway, a person must keep a lookout for vehicles and use caution to keep the animal under control.

(b) A person in charge of driving a herd of livestock on or across a highway shall position a person at the front of the herd to warn drivers that the herd is approaching.

(c) A person in charge of livestock being driven on a highway shall use reasonable care and diligence to open the roadway for vehicular traffic.

(d) If a horse or other livestock becomes frightened on a highway, the person riding or leading the livestock shall give a distress signal to an approaching driver by raising the person's hand.