A railroad track is not fenced within the meaning of AS 42.30.150 - 42.30.190 unless the track is guarded against the entrance of the livestock on either side and not more than 100 feet distant from the track by a fence constructed as required by law. Complete natural defenses against the entrance of stock, such as natural walls or deep ditches, are lawful fences within the meaning of AS 42.30.150 - 42.30.190 when they form, in connection with other legal fences, a continuous guard and defense against the entrance of livestock upon the track.
Alaska Legal Code