2011 ORS § 164.270¹
Closure of premises to motor-propelled vehicles
(1) For purposes of ORS 164.245 (Criminal trespass in the second degree), a landowner or an agent of the landowner may close the privately owned premises of the landowner to motor-propelled vehicles by posting signs on or near the boundaries of the closed premises at the normal points of entry as follows:
(a) Signs must be no smaller than eight inches in height and 11 inches in width;
(b) Signs must contain the words Closed to Motor-propelled Vehicles or words to that effect in letters no less than one inch in height;
(c) Signs must display the name, business address and phone number, if any, of the landowner or agent of the landowner; and
(d) Signs must be posted at normal points of entry and be no further apart than 350 yards.
(2) A person violates ORS 164.245 (Criminal trespass in the second degree) if the person operates or rides upon or within a motor-propelled vehicle upon privately owned premises when the premises are posted as provided in this section and the person does not have written authorization to operate a motor-propelled vehicle upon the premises.
(3) Nothing contained in this section prevents emergency or law enforcement vehicles from entering upon land closed to motor-propelled vehicles. [1981 c.394 §2]