What is an Ignition Interlock Device?

An ignition interlock device (IID) is installed in the car of a person who is convicted of a DUI offense. It’s also known as a breath alcohol ignition interlock device, and it works the same as a breathalyzer to measure the blood alcohol concentration (BAC) of a driver. The driver cannot start their car until they blow into the IID and prove their BAC is under .08 percent. Ignition interlock devices cost between $70 and $150 to install, and convicted drivers are responsible for paying this one-time fee.

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UPDATED: Apr 15, 2022

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Written By: Tonya SislerReviewed By: Brad LarsenUPDATED: Apr 15, 2022Fact Checked

Drunk driving is a serious problem that forever ruins the lives of many. Diligent efforts are being made to prevent drivers from getting behind the wheel after drinking, but the problem is still very dangerous and prevalent.

According to California’s Department of Motor Vehicles, first time DUI (driving while under the influence) offenders stand a 24 percent chance of being convicted again in the next five-year period. A second-offender has a 36 percent chance, and offenders with three convictions have close to a 50 percent chance of driving drunk and being caught again within five years.

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It would be nice to blame all drunk-driving accidents on repeat offenders, however, they only cause about 7 percent of accidents that result in fatalities. Nearly 20,000 are killed each year by non-convicted drunk drivers, and this leads advocates of the interlock device to recommend that the devices should become standard vehicle equipment for every driver.

What is an Ignition Interlock Device?

An ignition interlock device (IID) is a unit about the size of a cordless phone handset, and it is installed in the car of a person who has been convicted of a DUI (driving while under the influence) offense. It is also known as a breath alcohol ignition interlock device, and it works the same as a breathalyzer to measure the blood alcohol concentration (BAC) of a driver. The IID uses a fuel cell that is ethanol-specific, as an alcohol sensor. When breath with alcohol is blown into the unit, it essentially experiences a chemical oxidation, which generates electric current in the unit. The current is measured and then converted to a reading equivalent to the user’s BAC.

Who is Required to Use an Interlock Ignition Device?

Starting in 2009, most of the 50 states have enacted laws that permit IIDs to be used as a sentencing alternative in DUI convictions. In California for example, a driver can be sentenced to using an IID for up to three years from their conviction date. The benefit of using the interlock device is that it may shorten the amount of time that some repeat offenders will need to wait before they can apply for a restricted license.

How is the Ignition Interlock Device used?

A driver who has an ignition interlock device installed in their vehicle will need to exhale into it before they attempt to start their car. If their BAC is greater than the allowable level programmed into the device, which is usually .02 percent or .04 percent, the IID will prevent the car from being started. Additionally, while the car is in use, the IID will randomly request additional breath samples. This prevents the drivers from having someone else breathe into the device to start their car. The interlock device does not have the capability to actually turn off the car engine, however, if a driver does not provide an additional breath sample or the sample shows evidence of alcohol, the IID will add the event to its log, give the driver a warning and then start an alarm such as lights flashing or the horn honking, until either a clean breath sample has been given or the car has been turned off.

Effectiveness of the Ignition Interlock Device

Studies have been performed to measure the effectiveness of the interlock device. The conclusions so far are that the device works for some drivers in certain contexts, but not for every offender in every situation. Several studies found that by using the IID, the risk of repeat offenses has been cut by up to 65%. There is some evidence that even when an IID is not actually installed, a judicial order to install the device works just as well as an effective deterrent for repeat DUI drivers. In the state of California, drivers with repeat DUI convictions can install an IID to obtain a restricted driving privilege, and this has been shown to reduce subsequent DUI offenses. The device does not seem to be effective with first offenders that had high BACs.

Interlock Device Criticism

Some believe that sobriety devices used in cars can actually be dangerous. A second offender filed a lawsuit claiming that blowing into the device caused him to pass out and crash. He was sober at the time, but was a heavy smoker and said he blew so hard into the device that he passed out and hit a tree. Conversely however, in the state of Pennsylvania, the interlock device stopped nearly 34,000 would be drunk drivers from starting their cars, and that is the statistic for just one year. A 79-year-old woman claimed she could not breathe hard enough to get a reading on the device, and is suing the state of Florida, saying that she has shortness of breath and a requirement to use the IID violates the Americans with Disabilities Act. The device typically requires the user to take a deep breath and blow into it for up to 6 seconds.

The Effects of an Interlock Device on Auto Insurance Rates

One of the ways for DUI offenders to tell insurance companies that they are less of a risk is to install the IID into their vehicle. This sends a message that the driver is serious about their future sober driving commitment. Some marketers of the devices even claim that every family member, even those who have not been convicted of a DUI, should install the IID in their car as insurers will look favorably on them and provide reduced car insurance rates. A statistic from the Judicial Council of California says a teen that is convicted of a DUI should expect to pay over $40,000 in car insurance over the next 13 years after their conviction. Companies that sell insurance to persons convicted of a DUI typically charge approximately 25 percent more for the policy than they would a policy for a safe driver.

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Editorial Guidelines: We are a free online resource for anyone interested in learning more about car insurance. Our goal is to be an objective, third-party resource for everything car insurance-related. We update our site regularly, and all content is reviewed by car insurance experts.

Tonya Sisler has a Bachelor’s Degree from the University of South Carolina in Journalism and has worked for 15+ years in management. She has also completed a proofreading certification and is currently a professional writer.

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Written by Tonya Sisler
Insurance Writer Tonya Sisler

Brad Larson has been in the insurance industry for more than a dozen years. He started out as a claims adjuster for a national carrier. He has since switched to the agency side of the business. Brad is licensed in all P&C lines.

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Reviewed by Brad Larsen
Licensed Auto Insurance Agent Brad Larsen

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