Increasing Alcohol Ignition Interlock Use

At a glance

An alcohol ignition interlock is a breath-test device connected to a vehicle's ignition. Ignition interlocks reduce driving while impaired (DWI) repeat offenses by about 70% while they are installed. States may consider using the following eight key program features to strengthen state alcohol ignition interlock programs.

Overview

Keep your state safe—increase alcohol ignition interlock use.A

Ignition interlocks reduce driving while impaired (DWI) repeat offenses by about 70% while they are installed. All states have implemented ignition interlock programs to manage interlock issues and monitor offenders who are required or eligible to install them. Despite these laws and programs, only about one-fifth of those arrested for DWI have interlocks installed.

More comprehensive ignition interlock laws are effective in decreasing the number of impaired drivers in fatal crashes.1 Laws requiring an ignition interlock for all offenders were associated with 26% fewer alcohol-impaired (0.08 g/dL BAC) drivers in fatal crashes compared with no interlock law during 2001–2019.1 Laws requiring an ignition interlock for repeat and high-BAC offenders were associated with 20% fewer alcohol-impaired drivers in fatal crashes compared with no law during 2001–2019.1

What is an alcohol ignition interlock?‎

An alcohol ignition interlock is a breath-test device connected to a vehicle's ignition. The vehicle will not start unless the driver blows into the interlock and has a blood alcohol concentration (BAC) below a pre-set limit, usually 0.02 g/dL.

Eight key program features

States may consider using the following eight key program features to strengthen state alcohol ignition interlock programs. These key features were identified through a collaborative evaluationB that looked at characteristics of existing state interlock programs associated with increases in interlock use. Implementing just one of these key features is likely to increase interlock use. Implementing multiple key program features is associated with even higher increases in interlock use.

Key Program Feature

Characteristics of a Strong Program

Example

Require or incentivize use

Requirement or strong incentive to install interlocks

A law covering all offenders with significant reduction of hard license suspension period if interlock is installed

Levy strong penalties

Strong, swift, and appropriate penalties

Extension of interlock time, home monitoring, fail breath test, or tamper or otherwise circumvent interlock

Monitor interlocks to ensure proper use

Careful monitoring to assure interlocks are installed and used as intended

Random checks by Department of Motor Vehicles (DMV), probation, or treatment centers to ensure offender has installed and is using an interlock

Implement uniformly across state

Uniform and consistent implementation, statewide

All agencies report data regularly in compatible format, using uniform definitions of violations in same time frame

Coordinate across agencies

Close coordination and communication across all agencies

Regular communication with representatives from all interlock program-involved agencies

Educate stakeholders about the program

Regular training or education for all interlock agency staff and management

Regular trainings between interlock program managers, law enforcement, vendors, DMV, and court staff

Provide adequate resources

Adequate staff and funding resources

Designated interlock program manager and staff; financial assistance for offenders

Use data for action

Excellent data records (including level of offense, BAC level at time of arrest, number of prior arrests, installation/removal dates, violations)

Combined annual data on offenders available from all agencies to monitor offenders, report violators, and evaluate program effectiveness

  1. Unless otherwise noted by a numbered reference, the content for this page comes from the report and fact sheet linked above.
  2. Key program features were derived from an evaluation conducted in 2014 by the Centers for Disease Control and Prevention (CDC), the National Highway Traffic Safety Administration (NHTSA), and the Governors Highway Safety Association (GHSA) and produced by the Preusser Research Group. The evaluation looked at key features of interlock programs and use of interlocks in 28 states from 2006–2011. Each state's key program features were rated, and correlation analysis was used to determine which were related to higher interlock use. The full report, linked above, contains additional data, analyses, discussion, and examples of strong key program features from various states.
  1. Teoh ER, Fell JC, Scherer M, Wolfe DER. State alcohol ignition interlock laws and fatal crashes. Traffic Inj Prev. 2021;22(8):589–592. doi:10.1080/15389588.2021.1984439