Citation

Ramaekers JG, Lamers CTJ, Robbe HWJ, O'Hanlon JF. Proc. Int. Counc. Alcohol Drugs Traffic Safety Conf. 2000; 2000.

Copyright

(Copyright © 2000, The author(s) and the Council, Publisher International Council on Alcohol, Drugs and Traffic Safety)

DOI

unavailable

PMID

unavailable

Abstract

The purpose of the present studies was to empirically determine the separate and combined effects of .9-tetrahydrocannabinol (THC) and alcohol on actual driving performance. In the first study, eighteen recreational THC users were treated with drugs and placebo according to a balanced, 6-way, observer and subject blind, cross-over design. On separate evenings they were given THC placebo, THC 100 .g/kg and THC 200 .g/kg with and without alcohol. Alcohol doses were sufficient to sustain blood alcohol concentrations (BACs) of around 0.4 g/dl during testing. Subjects conducted two driving tests at each occasion: i.e. the Road Tracking Test and a Car-Following Test. In the second study 16 recreational users were treated with drugs and placebo according to a balanced, 4-way, cross-over, observer and subject-blind design. On separate evenings they were treated with THC placebo and THC 100 .g/kg with and without alcohol. As in the first study, alcohol doses were sufficient to sustain BACs of around 0.4 g/dl during testing. Subjects conducted a City Driving Test. Both THC doses alone, and alcohol alone, significantly impaired the subjects' Road Tracking and Car-Following performances. Both THC doses in combination with alcohol severely impaired the subjects' performance in each test. In the City Driving Test, the combination of THC 100 .g/kg and alcohol significantly reduced the frequency of visual search for traffic at intersections. While the effects of THC alone in doses up to 200 .g/kg might be categorized as "moderate", they become "severe" when THC is combined with a low dose of alcohol.

Keywords: Cannabis impaired driving; DUID; Ethanol impaired driving