In my decades of work in the ignition interlock industry, I have seen how confusing interlock requirements can be for drivers after a DUI. Even though the interlock device is one of the most effective tools for getting someone back on the road, most drivers have no idea how the rules work or what to expect until they are suddenly required to install one. The details can feel overwhelming at first, especially when the DMV and the court have different requirements.
My goal here is to explain ignition interlock devices in a simple and clear way, so you know what they are, why they are required, and how they fit into your DUI penalties.
What an Ignition Interlock Device Is
An ignition interlock device, often called an IID, or its “official” name is a BAIID (breathe alcohol ignition interlock device) is a small breath testing device that connects to your vehicle’s ignition system. The car will only start after you provide a clean breath sample.
The device will also require rolling re-tests while you drive. These checks help make sure the driver stays alcohol free during the trip.
Why California Requires Interlock Devices
California expanded interlock requirements to reduce repeat DUIs and allow drivers to keep driving legally. Instead of losing your license completely, the interlock gives you a safe and monitored way to stay on the road.
Research shows that interlocks help prevent alcohol impaired driving. This is one of the reasons the state relies on them so much.
Who Must Install an Interlock Device
Interlock requirements vary based on your case, but common situations include:
- first time DUI with alcohol
- repeat DUI offenses
- high blood alcohol levels
- cases involving accidents
- custody cases
Some counties have stricter enforcement than others.
How Long an Interlock Is Required
The length of time depends on:
- whether it is your first DUI
- your blood alcohol level
- whether injuries were involved
- whether you refused a chemical test
First time cases may require a few months (3 to 6). Repeat offenses can require a year or more.
How the DMV and the Court Affect Interlock Requirements
One of the most confusing parts is that the DMV and the court can each require an interlock device. Their rules do not always match.
For example: The DMV may require an interlock even if the court does not or the court may require an interlock even if the DMV does not.
This is why people sometimes think they are done with their requirements but still cannot clear their license.
What You Need To Install an Interlock
To install an interlock device, you will need:
- a CA State certified interlock provider
- proof of installation (Form 920)
- an active monitoring agreement
- regular calibration appointments
The installation provider sends proof directly to the DMV or courts but you will still need to take the form to the DMV and reinstate. Your time doesn’t start counting until this is done.
Life With an Interlock Device
Most people get used to the interlock quickly. At first it may feel strange, but after a few days it becomes part of your routine.
Drivers tell me the biggest adjustments are remembering to plan extra time to test before starting the car, rolling re tests, and attending calibration appointments.
These steps are required to stay in compliance.
What Happens If You Miss an Appointment or Test
If you miss a calibration appointment or fail to complete a required test, the device may enter a lockout state. This means your car may not start until the issue is resolved.
The DMV or court may also extend your interlock period or add penalties.
A Simple Way To Understand Interlock Requirements
- The interlock helps you keep driving legally
- Requirements vary by case and county
- The DMV and court can each set their own rules
- You must install, maintain, and complete all monitoring steps
Understanding these rules early helps you avoid delays and stay on track.
Closing Thoughts
An ignition interlock device can feel intimidating at first, but it is one of the most helpful tools for getting your driving privileges back. Once you understand how the device works and what is required, the process becomes much easier. With the right information and consistent follow through, you can complete your interlock period successfully.
Sources
California Vehicle Code Section 23700
California DMV Ignition Interlock Program Guidelines
California Office of Traffic Safety Research