The influence of cannabis and alcohol on driving.

Author(s)
Tunbridge, R. & Sexton, B.
Year
Abstract

This research had two primary objectives: Firstly, to provide reliable data, under laboratory conditions, on the impairing effects of the combination of moderate doses of cannabis and alcohol on driving. Secondly, to provide an overview of the attitudes and habits of cannabis and alcohol users in relation to driving and explore factors which may influence the decision to drive under their influence. There objectives were addressed using experienced cannabis and alcohol users carrying out laboratory-based tasks and driving in a simulator. Two cannabis conditions: placebo and low THC; and two alcohol conditions: placebo and a dose to give a breath alcohol level of approximately 50ug/100ml, were used. The few studies that have combined the effects of cannabis and alcohol on driving performance have used relatively high doses of alcohol and have been inconsistent in terms of methodology, making comparisons difficult. Anecdotal evidence suggests that regular cannabis users occasionally drink an amount of alcohol below the legal limit for safe driving, and then smoke cannabis before driving. It was therefore important to establish the degree of impairment caused by a moderate dose of alcohol in combination with cannabis. Results using the TRL driving simulator confirm the results from these previous studies. A reduction of average speed and an increase in headway on simulated motorway driving was observed with cannabis, whether or not alcohol was also consumed. A possible explanation for this is that drivers are aware of their impairment, but attempt to compensate for their impairment by driving more cautiously. Cannabis also adversely affected drivers tracking ability. In terms of road safety, it could not be concluded that driving under the influence of cannabis with or without alcohol, at the dose levels used in the study, is not a hazard. There are effects on various aspects of driver performance and these are unpredictable. (Abstract only) (Author/publisher) For the covering abstract of the conference see ITRD Abstract No. E201067.

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Publication

Library number
C 27972 (In: C 27945) /83 / ITRD E201148 (also at CD-ROM C 27890/C27945/C28028)
Source

In: Alcohol, drugs and traffic safety : proceedings of the 16th ICADTS International Conference on Alcohol, Drugs and Traffic Safety T'2002, Montreal, Canada, August 4-9, 2002, Volume 2, p. 499

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