Evaluation of a designated driver intervention to prevent alcohol-related road accidents in the clubs of Milan, Italy

Objective. The present study is an evaluation of a designated driver intervention. The objectives were: (1) to verify the intervention assumption, which is that offering incentives, linked to a positive result of the breathalyser test (<0.5 g/l) when leaving the club, leads to a decrease in the percentage of drivers leaving the club with a BAC above the legal limit; (2) to understand the reason why drivers take part in the intervention and assess whether the operation was effective in lowering the amount of alcohol consumed during the night; (3) to verify the assumption that there is a bias in the selection of designated drivers. Method: Pre-experimental research design with a control group and no pre-test. The two conditions of the independent variable were: presence or absence of the Safe Driver intervention. A group of drivers who took part in the intervention (DDs N=124) was compared with a group that did not (non-DDs N=139). Results. (1) DDs mean BAC was significantly lower than non-DDs, but (2) the incentive motivated just 5% of DDs to drink less, and (3) there is a bias in the selection of DDs that present a lower drinking risk profile than non-DDs. Discussion. The effectiveness of the intervention does not seem to be supported by strong evidence. The free-entrance incentive is not effective in motivating drivers to drink less. More research is needed to evaluate the effectiveness of designated driver interventions where the bias in the selection of drivers has been removed, by, for example, using other incentives and to have a clear understanding of designated drivers risk profile.