Evaluation of a program to motivate impaired driving offenders to install ignition interlocks

Approximately 30,000 alcohol ignition interlocks, which prevent a drinking driver from operating a vehicle, are in use in the United States and Canada. Currently available studies indicate that interlocks reduce impaired driving recidivism while on the vehicle. However, in the United States, the practical effectiveness of these devices is limited because few offenders are willing to install them in order to drive legally. This paper reports on a study of a court policy that created a strong incentive for impaired driving offenders to install interlocks by making penalties (e.g., jail or electronically monitored house arrest) the alternative to the interlock. Comparison of the recidivism rates of offenders subject to this policy with offenders in similar, nearby courts not using interlocks indicated that the policy was producing substantial reductions in DUI recidivism.