This paper examines the effect of alcohol on driving-related tracking tasks at 4 times of day in order to address concerns that the legal driving alcohol threshold in New Zealand (80 mg/dl blood) may have greater effects during the early afternoon/early morning than during evening/mid-morning. 16 male army personnel provided a homogeneous sample with respect to time-of-day characteristics. After a formal practice session, members of the sample performed lateral tracking tasks in 8 counterbalanced sessions, either with or without alcohol (0.836 g/kg), at 0900, 1300, 1800, and 0100 hours. The tasks varied in terms of smooth and ballistic motor pursuit, unpredictability and availability of target preview. Alcohol markedly impaired tracking accuracy, especially in nonpreview conditions. The only evidence for an overall time-of-day effect was on a ballistic pursuit nonpreview task, but there was no indication of any alcohol by time-of-day interactions. When tested 30 min after consumption of alcohol, sensorimotor tracking skills are markedly impaired at alcohol levels approaching the New Zealand threshold for legal driving, but these effects are not subject to circadian variations.
Abstract