Ignition Interlock Device Overview

An ignition interlock device is a form of breathalyzer that is attached to a vehicle’s dashboard. The device requires the operator of the vehicle to test his or her alcohol blood concentration prior to starting the engine. If the driver’s blood alcohol concentration is at or above the restricted level, the car will not start.

Ignition interlock devices are installed in the vehicles of repeat DUI offenders. The majority of states in the US now allow ignition interlock systems to be installed as a condition of probation, though the installation is often required for repeat offenders.

The six states that have now signed mandatory ignition interlock devices into law for DUI first offenders are:

  • New Mexico
  • Arizona
  • Illinois
  • Louisiana
  • Washington
  • Nebraska

The device is used as a direct preventative measure to deter the convicted driver from driving under the influence again. This solution is increasingly popular with government officials and officers because of its effectiveness in deterring future incidents. In addition, the offender pays for the installation and cost of the device, which is favorable to the court system.

Ignition interlock devices utilize fuel cell technology. An electric current is generated by the alcohol in the breath sample, producing a blood alcohol concentration level. Generally, the device is set to a low level, between .02% and .04%, so that if the drivers’ BAC is at or higher than this level, the car will not start.

In addition, the devices keep a record of activity that officers keep periodic tabs on in order to monitor the driver. As the vehicle remains in use, the driver is subjected to occasional breath tests as he or she drives to insure continued sobriety. These continual tests prevent an alternate driver from starting the vehicle for the convicted driver, then switching places.

According to research by the International Council on Alcohol, Drugs and Traffic Safety, ignition interlocks can lead to an average 40% – 95% reduction in the number of repeat DUI offenses when combined with monitoring.

Mothers Against Drunk Driving (MADD) states that approximately 135,000 vehicles currently have ignition interlock devices installed within the United States. MADD is lobbying to increase that number based on evidence from their research, which proves that these devices are 90% effective.

However, some argument over the accuracy of the ignition interlock systems remains. This debate surrounds the same arguments against the accuracy of breathalyzer tests and the controversy over effects of outside factors affecting the blood alcohol concentration level.