All 50 states and the District of Columbia have laws in place to protect the public from drunk drivers (e.g., driving is illegal with BAC at or above 0.08%).

In addition to stricter drunk driving laws, sobriety checkpoints and mass media campaigns, Ignition Interlock devices are highly effective at preventing repeat offenses while installed. Mandating interlocks for all offenders, including first-time offenders, will have the greatest impact according to

These “car breathalyzers” require the driver to blow into an attachment linked to the vehicle’s ignition before the vehicle can be started. If there is a certain level of alcohol in the breath sample, then the vehicle cannot be started. For first time offenders, a judge must now order the installation of the device if the offender had a blood alcohol concentration (BAC) of .15% or higher.

Previously, a judge was required to either order the installation of an interlock device or the suspension of vehicle registration privileges. But in 2010, the Governor of New Jersey signed into effect a new law for all DWI offenders concerning the Ignition Interlock device. Differing from the prior law, the current law requires that all second, third, and subsequent DWI offenders place an ignition interlock device on any vehicle “principally operated” by the offender.

The prior law required that a driver have an Ignition Interlock device installed in every vehicle “owned, used or regularly operated,” which meant all private vehicles and work vehicles, whether or not the driver owned them. The newer law only mandates that the driver place the device on a car principally operated, but because the term “principally operated” does not have a clear definition, it remains to be seen which vehicles will require the installation.

Aside from these amendments, the period of Interlock device installation has increased. Previously, the period of installation was 6-12 months for first time offenders and 1-3 years for second and subsequent offenders. Now, the installation time will last for as long as the license suspension period, then for an additional period after the driver gets his/her license privileges restored.

For example, a first-time offender with a seven-month license suspension will have to install an interlock device on the vehicle for seven months, plus an additional 6-12 months after getting the license back. For a second offender, the device must be installed during the two-year suspension period and then 1-3 years after the license is restored. For a third offender, the device must be installed for 10 years and then 1-3 years following the restoration of the license.

Additionally, there are preventive measures in place to help eliminate circumventing the device. Drivers must provide intermittent breath samples, which helps prevent possible abuse of the system such as drivers who may be over the limit getting friends to blow into the device on their behalf in order to start the vehicle. If an intermittent breath sample is not provided when required or the BAC level of the breath sample provided exceeds the ignition interlocks pre-set blood alcohol level, an alarm will be sounded—flashing of headlights, horn honking—until the ignition is turned off. Some ignition interlock devices also take a digital photograph of the person who is giving the breath sample.

All devices will log data about all breath samples given—including passes, warns and failures—and any attempts at circumvention or tampering, and any evidence is reported to the authorities. Ignition interlock devices are monitored and checked every 30, 60 or 90 days, and can be recalibrated if necessary.