Today's New York Times includes an article on automobile ignition interlocks, those devices that are designed to prevent a car from starting if the driver is alcohol impaired. The theme of the article is that technology has not developed to the point where it would make sense to require interlocks for all cars, as opposed to only the rides of drivers who have been convicted of drunk driving.
The interlock devices that are sometimes court-mandated cost about $125 to install, plus monthly maintenance fees of $60 to $75, according to the article. How do they work?
A related article talks about options for drivers who want to test their own blood alcohol content before they get behind the wheel. That article notes that these unofficial tests need not be accurate, but fails to note that the accuracy of police-administered breathalyzers also is highly questionable -- for evidence, read some of the posts (such as this one) at DUI Blog.
To start a car, the driver must puff a breath into the unit. To avoid cheating, the breath puff is measured and must be given in a uniquely identifiable way that would be hard for a person who is not the driver to duplicate. Inside the unit, a small fuel cell converts any alcohol into electrical energy, which is measured and recorded. If no alcohol is detected, the driver can start the car. If alcohol is detected, the system turns off the power to the ignition.
The breath puff isn’t just for starting cars. While driving, the driver must periodically blow into the system to keep the car running. Typically, the data is downloaded every 30 days and is available to probation officers and court officials.
Vice Squad checks in on ignition interlocks from time to time.