Breath alcohol concentrations of designated drivers

This study established breath alcohol concentrations (BrACs) and alcohol-related behaviors of designated drivers (DDs) to determine (a) whether DDs are abstaining from drinking, (b) whether alcohol-related behaviors of non-DDs and DDs were different, and (c) whether the alcohol consumption of DDs resulted in BrAC levels that affected driving performance or caused psychomotor impairment.

We conducted six anonymous field studies during a 3-month period in a southeastern college community restaurant and bar district. Intercept interviews were conducted with 1,071 bar patrons. Alcohol-related behaviors, BrAC, and whether one was serving as a DD were measured. The sample was primarily White (72.7%), male (62.4%) college students (64.7%). Descriptive statistics and an independent sample t test compared the BrACs of DDs versus non-DDs. A one-way analysis of variance examined the differences in the alcohol-related behaviors (Alcohol Use Disorders Identification Test-consumption [AUDIT-C] score) across DDs abstaining from drinking (BrAC = .00 g/210 L), drinking DDs (BrACs ≥ .02 and < .05 g/210 L), and impaired DDs (BrACs ≥ .05 g/210 L). A logistic regression assessed the impact of alcohol-related behaviors (AUDIT-C) on whether one was serving as a DD.

Of the 165 DDs, approximately 40% did not abstain from drinking. Approximately 17% of DDs had BrACs between .02 g/210 L and .049 g/210 L, whereas 18% recorded BrACs at .05 g/210 L or greater. The mean AUDIT-C score for impaired DDs significantly differed from both abstaining DDs and drinking DDs. Participants with greater AUDIT-C scores were more likely to serve as a DD and have a BrAC that significantly inhibited driving ability and psychomotor function.

These findings identify the need for consensus across researcher, layperson, and communication campaigns that a DD must be someone who has abstained from drinking entirely.