Ignition interlock in Massachusetts: who needs one and for how long
Massachusetts requires an ignition interlock device for drivers with two or more OUI offenses. The rule comes from Melanie's Law, passed in 2005, and is applied by the Registry of Motor Vehicles before it reinstates a license.
Last reviewed · Information, not legal advice
What an ignition interlock is
An ignition interlock device (IID) is a breath tester wired into a car's ignition. The driver has to blow into it before the engine will start. The device records the results, and the RMV uses those records to monitor drivers who are required to have one.
Who needs one
Massachusetts General Laws chapter 90, section 24½, part of the 2005 law known as Melanie's Law, sets the requirement. The RMV summarizes it this way: a person with two or more OUI convictions or assignments to a substance abuse or driver alcohol education program must have an interlock installed in their vehicle before the RMV issues a new license or reinstates a license or right to operate.
Two points follow from that:
- A 24D first offender disposition counts as an assignment. A person who had a 24D and is later convicted of OUI has two offenses for interlock purposes.
- Offenses from other states count. The RMV counts convictions and program assignments from any jurisdiction.
The RMV's conviction table marks the interlock as required for second, third, and fourth offenses and not required for a first offense.
How long it stays on
The RMV says that if you need an interlock and are granted a hardship license, you must keep the device for the length of the hardship license plus an additional two years after full reinstatement. If you wait out the full suspension instead, the RMV still requires the device as a condition of reinstatement; ask the hearings officer how long it must stay on in your case.
Once your license is restricted to interlock-equipped vehicles, driving a car without a certified, working device is a separate crime under M.G.L. c. 90, § 24S, punishable by a fine of $1,000 to $15,000 and at least 180 days in jail, of which at least 150 days must be served.
The steps
- Serve the waiting period. The suspension for a second offense is two years, a third offense eight years, and a fourth ten years, according to the RMV's table. Hardship license eligibility comes earlier in some cases; see the hardship license guide.
- Meet an RMV hearings officer. Mass.gov says you must meet with a hearings officer before installing an interlock, to be sure you are eligible for reinstatement.
- Install the device with an RMV-approved vendor and keep the paperwork.
- Pass the exams. For second and later offenses, the RMV requires a learner's permit exam and a road test before reinstatement.
- Follow the monitoring rules. Keep every service appointment the vendor and the RMV require. Ask the hearings officer what happens after a failed test or a missed appointment, because violations can cost you the license.
Costs
The driver pays for installation, monthly monitoring, and removal. Prices vary by vendor; ask more than one for a written quote that includes every fee.
If you live out of state
If you hold a license from another state, the RMV can still suspend your right to operate in Massachusetts, and your home state may apply its own interlock rules. Ask a lawyer licensed in Massachusetts and, if needed, in your home state.
Interlock rules have changed several times since 2005 and can change again. Confirm the current requirements with the RMV or a licensed Massachusetts attorney.
Who you will deal with
More offices, with notes, are on the local resources page.
Find local help
Listings come from public records or from the business itself. A listing is not a recommendation.
Common questions
Do I need an interlock for a first OUI in Massachusetts?
Under the RMV's current table, no: the interlock column for a first offense reads "No." The requirement starts with two or more OUI convictions or alcohol program assignments. Laws change, so confirm with the RMV.
Does a 24D disposition count toward the interlock requirement?
Yes. The RMV says the requirement applies to anyone with two or more OUI convictions or assignments to a substance abuse or driver alcohol education program. A 24D assignment counts as one.
Who installs the device?
Mass.gov says you must meet with an RMV hearings officer before installing a device, so the RMV can confirm you are eligible for reinstatement. Ask the hearings officer which vendors the RMV currently accepts.
Sources
Official sources checked on October 29, 2026.