Ignition Interlock Requirements After a New Jersey DWI
Reviewed by William A. Proetta, Esq. · Updated
Almost every DWI or refusal conviction in New Jersey now requires an ignition interlock device, a breath-testing unit wired into your car that won’t let it start if it detects alcohol. For most first offenses, the interlock replaces a long license suspension: you lose your license only until the device is installed. Since 2025, drivers who would otherwise serve a suspension can also earn one day of credit for every two days they drive with an interlock. William Proetta Criminal Law handles DWI and refusal cases across New Jersey.
How Long the Interlock Lasts
| Conviction | License forfeiture | Interlock |
|---|---|---|
| First DWI, BAC 0.08%–0.099% | Until the interlock is installed | 3 months |
| First DWI, BAC 0.10%–0.149% | Until the interlock is installed | 7 months to 1 year |
| First DWI, BAC 0.15% or higher | 3 months, starting after the interlock is installed | During the forfeiture, then 12 to 15 months |
| First refusal | Until the interlock is installed | During the forfeiture, then 9 to 15 months |
| Second DWI | 1 to 2 years | During the forfeiture, then 2 to 4 years |
| Third or later DWI | 8 years | During the forfeiture, then 2 to 4 years |
Sources: N.J.S.A. 39:4-50, 39:4-50.4a and 39:4-50.17. Drug DWI works differently; see drug DWI.
The 2025 Interlock Credit
Under the 2025 amendment, a driver ordered to forfeit their license can install an interlock instead and earn one day of credit against the forfeiture for every two days the device is installed. In practice, that lets many drivers keep driving, with an interlock, through what would otherwise be a full suspension.
The credit is not available when:
- the DWI involved a narcotic, hallucinogenic or habit-producing drug;
- the violation caused serious bodily injury to another person; or
- the conviction is for a commercial-vehicle DWI involving a controlled substance.
Living With an Interlock
- The device goes in the vehicle you own, lease or mainly drive, installed by a state-approved provider at your cost.
- While the order is in effect, you may not drive any vehicle without an interlock.
- Your license is marked to show the interlock requirement.
- The device asks for breath samples when you start the car and at random times while you drive, and it logs every result.
Driving without a required interlock, or tampering with one, is a separate offense with its own penalties. For the full penalty picture, see New Jersey DWI penalties and breath test refusal.
Ignition Interlock FAQs
Do I lose my license for a first DWI in New Jersey?
Usually only until the interlock is installed. At 0.15% or higher, there is also a 3-month forfeiture after installation, which the 2025 credit can shorten.
How long do I need an interlock for a first DWI?
3 months below 0.10%, 7 months to 1 year from 0.10% to 0.149%, and 12 to 15 months after the forfeiture at 0.15% or higher.
Does refusing the breath test mean an interlock?
Yes. A first refusal requires an interlock during the forfeiture and for 9 to 15 months after.
What is the 2025 interlock credit?
One day of credit against a license forfeiture for every two days you drive with an interlock. It does not apply to drug DWI or cases with serious bodily injury.
Can I drive someone else’s car?
Not unless it has an interlock installed under your order.
Talk to a New Jersey DWI Lawyer
The sooner we review the evidence, the more options you have. Call William Proetta Criminal Law at (732) 659-9600 for a free, confidential case review. Available 24/7, and se habla español.