Effects of ignition interlock license restrictions on drivers with multiple alcohol offenses: A randomized trial in Maryland

Objectives. This investigation sought to test the effectiveness of a statew ide ignition interlock license restriction program for drivers with multipl e alcohol-related traffic offenses. Methods. A total of 1387 multiple offenders eligible for license reinstatem ent were randomly assigned to participate in an ignition interlock program (experimental group) or in the conventional postlicensing treatment program (control group). The arrest rates of these 2 groups for alcohol traffic of fenses were compared for 1 year during the ignition interlock license restr iction program and for 1 year after unrestricted driving privileges were re turned. Results. Participation in the interlock program reduced offenders' risk of committing an alcohol traffic violation within the first year by about 65%. The alcohol traffic violation rate during the first year was significantly less for participants in the interlock program (2.4%) than for those in th e control group (6.7%). However, there was no statistically significant dif ference between these groups in the second year, after the interlock licens e restriction was lifted. Conclusions. Ignition interlock license restriction programs are effective at reducing recidivism among drivers with multiple alcohol offenses, at lea st while the restriction is in effect.