Drunker than you think: Delayed performance impairment from moderate amounts of alcohol
The goal of the research was to evaluate the effects of alcohol on the performance of New Zealand drivers across .05 and .08 BAC levels. An experimental test was conducted with 61 participants assigned to one of two alcohol dose conditions or a placebo control group. Comparison of alcohol doses showed that a BAC of .08 produced a level of impairment significantly worse than the placebo control. Impairment included edge and centre line crossings in the driving simulator, disinhibition of reactions to vehicles at intersections, higher peak speeds, and errors learning and recalling a computer-based maze. Drivers with a BAC of .05 also displayed some performance decrements, but not to the same degree as a BAC of .08, and with the exception of their steering reactions to hazards, not significantly different to the placebo control. An analysis comparing the impairment associated with peak and post-peak intoxication revealed that response disinhibition and participants self-ratings of intoxication showed acute tolerance (higher levels during ascending and peak BAC levels) while maze learning and recall errors, edge and centre line crossings, and maximum speeds showed acute protracted errors (poorer performance during the post-peak phase). This asymmetry is found even when equivalent BACs levels are compared during ascending and post-peak phases and occurred for both alcohol groups. Finally, participants were not able to accurately judge how much alcohol they had consumed or their level of intoxication (particularly the high dose group), and subjective ratings of intoxication were not a reliable indicator of their performance impairment.