Ignition interlocks keep drunks from driving.

Convicted drunk drivers will need more than their key to start their cars in a growing number of states. They'll also have to breathe into a tube on an ignition interlock, which can be installed on a car to prevent it from starting or running if it detects alcohol in the driver's breath.

All but seven states require or allow ignition interlocks, generally for repeat offenders. New Mexico became the first state to make them mandatory for all convicted drunk drivers, including first time offenders, with legislation that was passed in 2005.

In the 2006 legislative sessions, at least 12 states introduced bills regarding ignition interlock devices. Laws were passed in Arizona, Colorado, Delaware, Maryland and Wyoming.

* Arizona established an aggravated offense if a driver has an ignition interlock device and commits another drunk driving offense, including refusing a test, and requires certification rules for ignition interlock device installers and manufacturers.

* Colorado requires that ignition interlock restrictions be placed in the driving record of a convicted drunk driver and prohibits the person from driving any car not equipped with an ignition interlock device until the restriction is officially removed.

* Delaware requires the installation of an ignition interlock on all vehicles owned or operated by a driver convicted of a high BAC offense, with the duration determined by the BAC level of the offender.

* Maryland imposed a one-year ignition interlock requirement for offenders with a BAC of .15 or higher.

* Wyoming authorized a restricted license if an ignition interlock device is installed.

A summary of research on ignition interlocks is available from the Traffic Injury Research Foundation. For more information, visit www.trafficinjuryresearch.com.