How necessary is monitoring to interlock program success?

Objective: Numerous studies have demonstrated that vehicle alcohol ignition interlocks installed on the cars of impaired-driving offenders reduce recidivism by approximately two-thirds in comparison to similar offenders whose licenses have been suspended. An unresolved issue is the extent to which the effectiveness of interlock programs can be improved by close monitoring of the offenders' performance while in the program. This article describes 5 types of monitoring currently being used in interlock programs in the United States.

Methods: The programs reviewed vary from those that simply ensure that the interlock is on the offender's vehicle and functioning, to those that use the interlock log data to extend the length of time the offender is required to be in the interlock program, and those that use the interlock data to initiate special monitoring and treatment programs that must be completed before removal of the interlock device. The strengths and limitations of each type of program are described. Also reviewed are current technological developments that appear to be leading to the development of fully automated interlock monitoring systems.

Results: Initial evidence shows that more intensive monitoring provides benefits in improved performance on the interlock, as indicated by fewer high blood alcohol concentration (BAC) breath tests when attempting to drive. Although effective, supervision that is more intensive increases government program costs.

Conclusions: The relative cost-effectiveness of the differing types of monitoring requires investigation. Treatment programs need to be integrated with the interlock installation period. New technologies can potentially reduce interlock offender monitoring costs and effectiveness. Integrating treatment with the interlock could have postinterlock benefits.