For the purposes of this Chapter 10.84, a person is under the influence of an alcoholic beverage or any drug, or the combined influence of an alcoholic beverage and any drug, when as a result of drinking an alcoholic beverage or using a drug, or both, his or her physical or mental abilities are impaired to a degree that he or she no longer has the ability to operate a motor vehicle, boat, vessel or aircraft with the caution characteristic of a sober person of ordinary prudence under the same or similar circumstances. For purposes of this Chapter, the presumptions prescribed in Section 23152 and 23255 of the Vehicle Code shall apply.
(Ord. 541, 1989).