BAC Feedback Lowers Perceived Intoxication and Increases Perceived Driving Fitness

Driving under the influence (DUI) is one of few offenses in which guilt can be determined by a single measure (i.e., legal limit = 0.08% BAC). Drivers perform poorly when estimating their intoxication, yet the degree to which they perceive themselves to be intoxicated strongly predicts their decision to drive. Despite more prevalent breathalyzer use, it is unclear whether feedback that drivers' BAC approximates the legal limit dissuades the decision to drive. This study tested the effect of providing BAC feedback on drinkers' perceptions of their intoxication and driving fitness after drinking alcohol.

Sixty-one drivers were randomly assigned to the control (C) (n=30) or feedback (F) (n=31) group. Participants attended three sessions (pre-feedback, feedback, post-feedback) during which they received 0.65g/kg alcohol (target BAC ≈ 0.08%). During the pre- and post-feedback sessions, groups rated their level of intoxication and perceived driving fitness. During the feedback session, those in the feedback group received explicit information about their actual BAC, while those in the control group received no information.

Prior to receiving feedback, the groups did not differ in perceived intoxication and driving fitness. After receiving feedback, however, Group F perceived lower intoxication and greater driving fitness than Group C. These group differences occurred despite comparable BACs among the groups throughout the study.

Receiving feedback that one's BAC approximates the legal limit may not increase the driver's perceived risk of driving.