You might see this in a court order, DMV notice, or a lawyer's letter saying someone must install an "ignition interlock device" before driving again. That means a small breath-testing machine is connected to a vehicle's ignition system. Before the car will start, the driver has to blow into it, and if the device detects alcohol above a set level, the engine stays off. Many systems also require retests while the car is being driven.

Practically, it is meant to prevent repeat drunk-driving incidents while still allowing limited driving for work, medical appointments, or family care. The device usually comes with fees, service appointments, calibration requirements, and strict rules. Missing a retest, trying to tamper with the unit, or having someone else blow into it can lead to more penalties, longer restrictions, or problems with a driver's license suspension or probation.

In Hawaii, courts and the Administrative Driver's License Revocation Office may require interlock use after an OVUII arrest or conviction under Hawaii Revised Statutes Chapter 291E. For example, Act 57 (2018) expanded Hawaii's ignition interlock requirements for certain drunk-driving cases. If a crash caused injuries, device records may matter in a personal injury claim. Evidence that a driver ignored interlock rules or drove after drinking can support arguments about negligence, liability, and sometimes punitive damages.