The efficacy of experimental interventions designed to reduce drinking among designated drivers

Designated drivers are a popular strategy for avoiding drunk driving. However, studies have demonstrated that the strategy is often implemented poorly, resulting in diminished risk-reduction effectiveness. The purpose of this study was to test the efficacy of six interventions designed to reduce alcohol consumption among designated drivers.

A total of 376 groups consisting of 1,412 pedestrians (57.8% men) were recruited as they crossed into Tijuana, Mexico, from San Diego, CA. Before crossing into Mexico, each group was assigned at random to one of six experimental conditions or to one control condition. The six interventions were designed to (1) cue the use of designated drivers, (2) change attitudes about designated drivers, (3) provide monetary rewards for driver sobriety, and (4) increase group supportive norms for proper designated driver use. Participant breath alcohol concentrations (BrACs) were collected before entering Mexico and on return to the United States.

Using group members to deliver pro-designated driver messages significantly decreased driver and passenger BrACs relative to controls. Male drivers were more likely to return from Mexico with BrACs of zero if they were rewarded. Among female drivers, wearing a bracelet with the printed words "designated driver" in addition to cuing resulted in 9 of 10 drivers returning with BrACs equal to zero.

These results demonstrate that designated driver sobriety can be enhanced through brief interventions, and proper use of the designated driver concept did not increase the risk of excessive alcohol consumption for passengers.