ISS stands for "Ignition Interlock System" — a device that prevents your car from starting if it detects alcohol on your breath
An ISS restriction on your driver's license means you are required by law to have an ignition interlock device installed in any vehicle you drive. The device measures your breath alcohol content before the engine will turn over. If the reading exceeds the legal limit set by your state (usually 0.02% for restricted licenses), the car will not start. You cannot remove the device yourself or drive a vehicle without one installed.
ISS restrictions are court-ordered consequences, most commonly imposed after a DUI or DWI conviction. Some states also impose them after a refusal to take a breath or blood test, or after multiple traffic violations involving alcohol. The length of time you must maintain the device varies by state and by the specifics of your case — typically between 6 months and 3 years.
The restriction appears on your license as a code or notation so that law enforcement can see at a glance that you are required to use the device. Driving a vehicle without an interlock device installed when your license carries an ISS restriction is a separate criminal offense in most states, even if you are not impaired.
Key Takeaways
- An ISS restriction requires you to install an ignition interlock device in every vehicle you operate, and the device must be functioning before your car will start.
- The restriction is imposed by a court as part of a DUI, DWI, or related conviction, and you cannot have it removed early without a judge's order.
- You are responsible for paying the installation, calibration, and monthly monitoring fees, which typically range from $60 to $200 per month depending on your state and provider.
- Driving any vehicle without an active interlock device while your license carries an ISS restriction is a separate criminal violation and will result in additional charges.
- Some states allow you to request a hardship exemption for a single vehicle used for work, but the device must still be installed in all other vehicles you own or operate.
How the ignition interlock device works in practice
When you get into your vehicle, you must blow into the device's mouthpiece before you can start the engine. The device analyzes your breath and displays a result. If your blood alcohol content is below the threshold your state has set, the engine will start normally. If the reading is at or above the limit, the engine will not turn over, and the device will log the failed attempt.
Most devices also require you to provide rolling retests while you are driving — typically every 5 to 15 minutes after you have been on the road for 5 to 10 minutes. These retests prevent someone else from blowing into the device at startup and then you driving impaired. If you fail a rolling retest, the device will log it, sound an alarm, and may flash the lights or honk the horn until you pull over and turn off the engine.
The device stores all test results — both passes and failures — in its memory. A technician downloads this data during your monthly calibration appointment. If the data shows repeated failed tests, missed rolling retests, or attempts to tamper with the device, your case officer or probation officer will be notified. This can result in license suspension, extended ISS requirements, or criminal charges for violation of your court order.
Installation, costs, and your responsibilities
You must have the device installed at a certified provider in your state. Your court order or DMV paperwork will list approved vendors, or you can contact your local DMV to find one. Installation typically takes 30 minutes to 1 hour and costs between $100 and $300, depending on your vehicle and your state.
After installation, you are responsible for monthly calibration appointments. These appointments take 15 to 30 minutes and cost $60 to $100 per visit. Some states require calibration every 30 days; others allow 60-day intervals. Missing a calibration appointment is a violation of your court order and can result in license suspension or additional penalties.
You also pay a monitoring fee, usually $50 to $100 per month, which covers the data transmission and case management. Some providers bundle installation, calibration, and monitoring into a single monthly fee; others charge separately. Request an itemized cost breakdown from your provider before you commit, because prices vary significantly by vendor and by state.
If your vehicle breaks down or is in the shop, you cannot drive another vehicle without an interlock device installed in it — even if you own that vehicle. You must either have the device transferred to the other vehicle (which costs $100 to $200) or arrange alternative transportation. Some states allow a temporary exemption for a rental car if you provide proof of the rental agreement, but the rental must have an interlock device installed before you can drive it.
State-by-state differences in ISS requirements
The threshold alcohol level, the length of the ISS requirement, and the rules around exemptions vary by state. Some states set the threshold at 0.02% for all ISS-restricted drivers; others use 0.04% or 0.05%. Your court order will specify the exact threshold for your device.
The duration of the ISS requirement depends on your conviction history and your state's law. A first-time DUI conviction typically results in 6 months to 1 year of ISS; a second conviction usually means 1 to 3 years; a third or subsequent conviction can mean 3 to 5 years or longer. Some states impose ISS automatically; others allow judges discretion. A few states allow you to request early removal after you have completed half the required period, but this requires a court hearing and is not may provide.
Hardship exemptions also differ by state. Some states allow you to request an exemption for a single vehicle used exclusively for work, medical appointments, or court-ordered treatment. Others do not allow any exemptions. If your state does allow an exemption, you must file a petition with the court and provide documentation of the hardship — typically a letter from your employer, a medical provider, or a treatment facility. The court must approve the exemption in writing before you can drive an exempt vehicle.
What happens if you violate your ISS restriction
Driving a vehicle without an active interlock device while your license carries an ISS restriction is a separate criminal offense. You can be charged with violating the terms of your sentence or probation, even if you were not impaired at the time. This charge is in addition to any other violations you may have committed, such as speeding or reckless driving.
Consequences for an ISS violation typically include license suspension (often for 6 months to 1 year), additional fines ($500 to $2,000 or more), and possible jail time (usually 10 to 30 days for a first violation). Your probation or parole may be revoked, which could result in serving the remainder of your original sentence in custody. Your ISS requirement may also be extended by 6 months to 2 years.
Tampering with the device — attempting to bypass it, disconnecting it, or having someone else blow into it for you — is also a criminal offense. Tampering charges carry the same penalties as driving without the device and often result in when ready license suspension and arrest.
Removing the ISS restriction from your license
When you have completed the required ISS period, you must have the device removed by a certified technician and obtain a removal certificate. The technician will provide this certificate to you and will send a copy to your state DMV. You cannot straightforward stop using the device; the removal must be documented.
After the device is removed and the DMV receives the removal certificate, you must visit your local DMV office to have your license reissued without the ISS restriction. Bring the removal certificate, your current license, and any other documents your state requires for license renewal. There is usually a small fee for the reissue (typically $10 to $30). Your new license will not carry the ISS code.
If you believe you have grounds to request early removal — such as completing a treatment program, maintaining a clean driving record, or demonstrating financial hardship — you can file a petition with the court that imposed the restriction. The court will review your petition and may grant early removal, but this is not automatic and varies by judge and by state. You will need to provide documentation of your circumstances and may need to appear in court for a hearing.
Frequently Asked Questions
Can I get an ISS restriction removed before my court-ordered period ends?
Some states allow early removal through a court petition, but it is not may provide. You typically must show that you have completed a treatment program, maintained a clean driving record, or faced genuine financial hardship. Contact the court that imposed the restriction or your probation officer to learn whether your state allows early petitions and what documentation you will need to provide.
What if I cannot afford the monthly interlock fees?
Contact your local legal aid office or a DUI defense attorney to ask whether your state has a fee waiver or reduction program for low-income drivers. Some states allow judges to reduce or waive fees in cases of documented financial hardship. You may also ask the court to extend your ISS period in exchange for a lower monthly fee, though this is not always an option.
Can I drive someone else's car if it has an interlock device installed?
Yes, as long as the device is functioning and you provide a valid breath sample that is below the threshold. You are not required to be the owner of the vehicle. However, you cannot drive any vehicle that does not have an active interlock device installed, even if you are not the owner.
Do I have to tell my employer about the ISS restriction?
You are not required to disclose the restriction to your employer unless your job involves driving a company vehicle or unless your employer has a policy requiring disclosure of license restrictions. However, if you need to drive for work, your employer will likely notice the interlock device. Some employers allow employees to request a hardship exemption for a work vehicle, which you can then present to the court.
What if the interlock device malfunctions or gives a false positive?
Contact your device provider when ready and request a recalibration or replacement. Keep a record of the malfunction and any communication with the provider. If the device fails during a rolling retest, document the time and location. Bring this documentation to your next appointment with your probation officer or case manager. A pattern of malfunctions may be grounds to request a device replacement or, in rare cases, a temporary exemption while the issue is resolved.