Good news: the system works. An alleged drunk driver was arrested for his fifth offense recently in Madison, Wisconsin.

The car wasn’t weaving or crashing into anything. But its horn was blasting away at regular intervals, and its lights were flashing. That’s a sign that the driver has failed an ignition interlock breath test, or refused to take one while driving. As a result, the device did what it was designed to do and alerted the town that a someone was behind the wheel who shouldn’t have been.

What Ignition Interlocks Do

An ignition interlock, or car breathalyzer, prevents a vehicle from starting if the driver has been drinking. According to Wisconsin law, repeat OWI offenders must install the devices. In order to start the vehicle, the driver must blow into the device, which registers the amount of alcohol on his or her breath. If just about any alcohol at all is present, the device will register a warning and keep the vehicle shut off for a few minutes. That interval gets longer if the driver fails repeated tests.

Ultimately, after a set number of failures, the driver is locked permanently, and the vehicle must be brought to the interlock provider for resetting, and to have data downloaded for the authorities.

The result: the public is protected from a driver who tries to get behind the wheel drunk.

What Happened Here

It’s not enough to give a driver an ignition interlock breath test before he or she sets out. What if the drinking starts after the test? To prevent that, an ignition interlock requires a rolling re-test. A beep sounds, and the driver must breathe into the device while driving, to ensure that sobriety is maintained.

This particular offender must have ignored the rolling re-test – perhaps he started drinking after getting underway. To attract the police, the car began flashing lights and honking the horn. The result was an OWI arrest.

What Ignition Interlocks Don’t Do

One thing ignition interlocks can never do is stop a vehicle when it’s driving. The device is wired only to the starter, lights and horn. Under no circumstances will it ever shut off an engine.

So the system worked, and a repeat drunk driver was removed from the road, following proof that he wasn’t able to stick to sober driving. That’s what makes ignition interlock programs so popular, and why Wisconsin’s needs to be extended, as 30 states’ programs are, to all drunk driving offenders, not just repeat offenders.

The technology works. Wisconsin just needs to work it a little better.