Ignition Interlock Devices and Car Insurance

What the device is and who needs one

An ignition interlock requires a breath sample below a set alcohol threshold before the engine will start, and periodically while driving. Every state has an interlock law; most now require or strongly incentivise one for first offenders, and nearly all require one for repeat or high-BAC offenses. Highway-safety research associates interlock programmes with substantial reductions in repeat impaired-driving offenses while the device is installed. The requirement typically runs from several months to two years and is a condition of driving on a restricted licence.

Does an interlock affect your premium?

Not directly. Insurers rate the DUI conviction, not the device. A handful of insurers have experimented with modest discounts for interlock participants, but it is not widespread, and no insurer surcharges for having one. Where the interlock matters is indirectly: it is often a condition of having any licence at all, and a licence—even restricted—is what makes you insurable as a driver rather than as an excluded household member.

Practical interactions with insurance

• You need an insured car to install it on. Installers require proof of registration and insurance. If you do not own a car, you cannot complete an interlock requirement on a non-owner policy; you will need a vehicle titled to you or an arrangement with the owner.
• Restricted licences are licences. Insurers can and do write policies for drivers on interlock-restricted licences. Disclose the restriction when asked.
• Device costs are yours, not the insurer's. Expect an installation fee plus a monthly lease, typically in the range of $70–$150 a month, plus calibration visits. Budget for it alongside the higher premium.
• A clean interlock record is evidence. Some insurers ask about programme completion; a record with no failed tests supports your case for standard pricing when the surcharge period ends.

Who else drives the car

Everyone who drives an interlock-equipped vehicle must blow into the device, including other household members. If another driver fails a test, the event is logged against the device holder. For insurance, this is a reason to make sure every regular driver of that vehicle is listed on the policy and understands the device—an unlisted driver in a crash is a larger problem than the failed test.

After the interlock period

Completing the interlock period usually leads to a full licence reinstatement. It does not end the insurance surcharge, which runs on its own schedule. Use the reinstatement as a trigger to re-compare quotes: you now have a documented period of compliant driving to point to, and some insurers weigh that in tier assignment.