Do designated drivers drink? an event-level analysis of impairment levels among designated drivers

Objective: The study established breath alcohol concentrations (BrACs) and alcohol-related behaviors of designated drivers (DDs) to determine: (1) whether DDs are abstaining from drinking, (2) if alcohol-related behaviors of non-DDs and DDs were different; and (3) whether the alcohol consumption of DDs resulted in BrAC levels that impact driving performance or caused psychomotor impairment.

Method: We conducted six anonymous field studies during a three-month period in a southeastern college community 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%). Independent sample t-test compared the BrACs of DDs versus non-DDs. A one-way ANOVA examined the differences in the alcohol-related behaviors (AUDIT-C score) across DDs abstaining from drinking (BrAC = 0.00), drinking DDs (BrACs ≥ 0.02 & < 0.05), and impaired DDs (BrACs ≥ 0.05). Logistic regression assessed the impact of alcohol-related behaviors (AUDIT-C) on whether one was serving as a DD.

Results: Of the 165 DDs, approximately 40% did not abstain. Approximately 17% of DDs had BrACs between 0.02 and 0.049, while 18% recorded BrACs at 0.05% or greater. 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.

Conclusions: These findings identify the need for consensus that a DD must be someone who has abstained from drinking entirely.