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Alcohol Ignition Interlocks For Convicted DUI Offenders

One of the most effective countermeasures available to jurisdictions to separate drinking from driving is the alcohol ignition interlock. The interlock requires that a DUI offender blow into the device, which is connected to the starter or other on-board computer system, in order to start the vehicle. If the breath sample registers a BAC above a defined pre-set limit, the vehicle will not start. The device also requires repeated breath tests while the vehicle is in use to ensure the DUI offender continues to remain sober throughout the duration of their trip.

There is a substantial body of literature that confirms the effectiveness of interlocks in reducing DUI. Studies demonstrate that while alcohol interlocks are installed in the vehicle, recidivism is reduced among both first and repeat DUI offender populations.

  • More than 10 evaluations of interlock programs have reported reductions in recidivism ranging from 35-90% with an average reduction of 64%.
  • A recent study commissioned by the Centers for Disease Control and Prevention (CDC) that involved a systematic review of 15 peer-reviewed studies on interlocks revealed that, while the devices were installed, the re-arrest rate of offenders decreased by a median of 67% compared to groups who never had an interlock installed.

This strong convergence of scientific evidence has led to substantial growth in interlock programs within the last decade, along with a shift toward mandatory interlock laws for all DUI offenders.

At present, all 50 states have passed some form of interlock legislation and achieved different degrees of program implementation. Currently, 24 states and four counties in California have passed mandatory interlock provisions for all DUI offenses, including first offenses.

However, more work is needed to strengthen existing practices and increase program participation rates. Interlocks are installed by only 22% of individuals arrested for DUI.

As part of a comprehensive solution to eliminate drunk driving, supports the mandatory and effective use of interlocks for all convicted DUI offenders. However, simply passing interlock legislation does not necessarily translate into positive outcomes. Effective use of IIDs also requires proper assessment and treatment, supervision, and verification of installation for all offenders ordered to install the device.

The implementation of monitoring and accountability frameworks to promote offender behavior change has been identified as an important priority in the improvement of existing interlock programs. is in agreement that interlock programs should be enhanced through the inclusion of assessment and treatment requirements. Read our complete policy position here.

Additional resources:

The Implementation of Alcohol Interlocks for First Offenders: A Case Study (TIRF)

The Implementation of Alcohol Interlocks for Offenders: A Roadmap (TIRF)

Ignition Interlocks: What You Need to Know (NHTSA)

Case Studies of Ignition Interlock Programs (NHTSA)

Alcohol Interlock Curriculum for Practitioners (TIRF)

State Ignition Interlock Laws (NCSL)

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