Self-underestimation of BAC as a predictor of risky driving in heavy drinkers

Background: Alcohol-related driving fatalities persist as a public health issue in the United States. Recent studies have focused on the role of driver risk-taking in DUI occurrences and consequent driving fatalities. This laboratory study examined simulated driver risk-taking under an acute dose of alcohol and a placebo to test the degree to which individual differences in risk-taking were predicted by drivers’ self-appraisal of their intoxication and the degree to which alcohol impaired their inhibitory control. Methods: Eighty young adult drivers (41 men and 39 women) received 0.65 g/kg alcohol (target BAC=80 mg/dL) or a placebo in a counterbalanced order on two different days and performed a simulated driving test that measured driver risk-taking as reduced distance to other vehicles. A cued go/no-go task measured drivers’ inhibitory control, and their perceived intoxication was assessed via self-reported intoxication and BAC estimation. Results: Compared with placebo, alcohol increased driver risk-taking, impaired inhibitory control, and increased perceived intoxication. The riskiest drivers under alcohol were those with the lowest estimations of their BAC. Tolerance to the subjective effects of alcohol might explain this relationship as the underestimators had heavier drinking histories. Discussion: The findings indicate that risky driving under alcohol could result in part from BAC underestimation, possibly owing to the development of alcohol tolerance. Sustained heavy drinking might reduce perceived intoxication and, consequently, the perceived need to compensate for potential impairing effects of alcohol while driving. The evidence suggests that drivers’ proclivity to risk-take under alcohol might depend largely on their self-appraisal of intoxication.