Ignition interlock devices that are connected to breath analyzers are a countermeasure that has only recently been investigated. In theory, an interlock device prevents an intoxicated individual from starting a motor vehicle. It is an automated system designed to control intersecting risk behaviors (drinking and driving) rather than either behavior separately. In the current study, a total of 1,387 multiple offenders eligible for license reinstatement were randomly assigned to participate in an ignition interlock program (experimental group). The arrest rates of these two groups for alcohol traffic offenses were compared for 1 year during the ignition interlock license restriction program and for 1 year after unrestricted driving privileges were returned. The study found that participation in the interlock program reduced offenders' risk of committing an alcohol traffic violation within the first year by about 65 percent. The alcohol traffic violation rate during the first year was significantly less for participants in the program (2.4 percent) than for those in the control group (6.7 percent); however, there was no statistically significant difference between these groups in the second year, after the interlock license restriction was lifted. 1 table, 2 figures, and 16 references