What is an Ignition Interlock?

The original ignition interlock devices are in-car breathalyzers that measure a driver’s blood alcohol concentration (BAC) through a breath sample. If the sample registers above the pre-set level—normally calibrated between 0.02 and 0.04 percent BAC—the engine will not start.

These devices were originally developed for the most dangerous drunk drivers: high-BAC, repeat offenders. But now anti-alcohol activists have set their sights on forcing interlocks into the cars of the 176 million American adults (21 and older) who drink responsibly. In 2006, Mothers Against Drunk Driving (MADD) convened a panel with the sole purpose of investigating new alcohol-sensing technologies specifically targeting citizens who have never been arrested or charged with DWI.

Saab, Nissan, Toyota, and other car manufacturers are already developing new interlock technology to initially be offered as optional equipment as soon as Fall 2008. In 2007, Nissan Motors unveiled a concept car fit with odor sensors to “sniff” any alcohol in the cabin. Soon after that, Volvo contracted Alcohol Countermeasure Systems Corp to customize interlocks for its vehicles.

But the choice will not be optional for long. With anti-alcohol activists and policymakers lobbying for mandatory technology in every vehicle, you could soon find yourself stranded by one of these devices in your car.

Optical Scan—a dashboard-mounted camera that monitors the movement of driver’s face and eyes to assess sobriety.
Transdermal Test—a detector built into either the gear-shift, steering wheel, or seatbelt buckle to measure the amount of alcohol in the driver’s sweat.
Odor Sensors—multiple sensors that are incorporated into the driver and passenger seats to detect any presence of alcohol from the air inside the cabin.
Alcokey—a patented system by Saab that incorporates a breath analyzer into the car key.
Ignition Interlock—the traditional dashboard-mounted breathalyzer that periodically tests driver’s breath through a blow tube.