The Ignition Interlock Device (IID) in California is a small device that prevents a driver from starting a vehicle on which the device is installed without first passing a breathalyzer test. The breathalyzer test detects the presence of alcohol on the breath. A driver fails a test when the IID detects a blood-alcohol concentration above .029 percent. According to the International Council on Alcohol, Drugs and Traffic Safety, IIDs, combined with other rehabilitation programs, lead to a 40-95 percent reduction in drunk driving offenses.
If a driver fails to pass an IID test, the vehicle to which the IID is attached won't start. If a driver passes the IID test, the vehicle will start and the driver can begin driving. The IID will continue to ask for retests, called "rolling retests," of the driver. These occur five to 15 minutes after the first start, and at random times in 45-minute cycles. If a driver fails a rolling retest, the IID logs the failure, and warns the driver to pull over. It can also turn on the horn and flashing lights of the vehicle.
The IID is not meant to change the behavior of a drunk driver alone. Instead, it helps notify surrounding drivers of the vehicle to stay away, thereby helping to avoid possible collisions. For those who fail the IID test before the vehicle starts, it ensures their vehicle is not on the road while they are intoxicated, again, avoiding potential collisions.
There are two rumors about the consequences of a failed IID test. If a driver fails a rolling retest, the vehicle does not suddenly turn off. The IID also does not signal through radio or wireless data transfer to law enforcement that a driver failed an IID.
