Background: An ignition interlock device is part of a multi-dimensional programme aimed at reducing recidivism in convicted drink drivers. To operate a vehicle equipped with an ignition interlock device, the driver must first provide a breath specimen. If the breath alcohol concentration of the specimen exceeds the predetermined level, the vehicle will not start. As a measure to reduce circumvention of the device (i.e. someone else blows into the mouthpiece), random retests are required while the vehicle is running. Other components of the drink driving programme include information seminars for the driver and downloading data from the device's data logger, which logs all test attempts and records all passes, warnings and failures.
Objectives: To systematically assess the effectiveness of ignition interlock programmes on recidivism rates of drink drivers, by examining rates of recidivism while the ignition interlock device was installed in the vehicle and after removal of the device.
Search strategy: The Cochrane Controlled Trials Register was searched, in addition to relevant electronic databases and the Internet.
Selection criteria: Controlled trials in which offenders have been charged with drink driving and have either been sentenced to participate in an ignition interlock programme or the usual punishment (either licence suspension or some form of treatment programme). This study was not restricted by language or status of publication.
Data collection and analysis: One randomised controlled trial (RCT) and ten controlled trials were identified, and also three ongoing trials. Data regarding recidivism while the interlock is installed in the vehicle; after the interlock has been removed from the vehicle and total recidivism during the study were extracted and entered into analyses using RevMan.
Main results: The RCT showed that the interlock programme was effective while the device was installed in the vehicle; relative risk 0.36 (95% confidence interval 0.21 to 0.63). Controlled trials support this conclusion, with a general trend - in both first-time and repeat offenders - towards lower recidivism rates when the interlock device is installed. Neither the RCT nor the controlled trials provide evidence for any effectiveness of the programmes continuing once the device has been removed.
Reviewers' conclusions: In order to eliminate potential selection bias, more RCTs need to be conducted in this area so that effectiveness, as well as efficacy, can be ascertained. The interlock programme appears to be effective while the device is installed in the vehicle of the offender. Studies need to address ways of improving recidivism rates in the long term, as the major challenges are participation rates, compliance and durability.