Ignition Interlock
An ignition interlock is an in-vehicle alcohol breath testing device that prevents a vehicle from starting if alcohol is detected. In Ontario, ignition interlock is mandatory for drivers who have been convicted of most impaired driving and over 80 offences, as a condition of licence reinstatement after a driving prohibition.
Drivers must drive only the vehicle equipped with the device. Driving an unequipped vehicle, attempting to bypass the device, or having someone else blow into it are separate offences that can lead to program extension and additional charges.
How the device works
Before starting the vehicle, the driver blows into the device. If alcohol is detected at or above the program threshold (typically 20 mg/100 mL of blood), the vehicle will not start. While driving, the device requires periodic rolling re-tests. Failed or missed re-tests are logged, and the device may activate the vehicle's lights and horn until the driver pulls over and turns off the ignition. All events are recorded and reviewed by the program administrator.
Ontario's program streams
Ontario's ignition interlock program operates in three main streams. Stream A — Reduced Suspension with Ignition Interlock: available to first-time offenders meeting eligibility requirements; allows licence reinstatement during what would otherwise be the driving prohibition period, with mandatory interlock for the program duration. Stream B — Standard: the default stream after the full driving prohibition has been served; mandatory interlock for one year for a first conviction, three years for a second, and lifetime for a third — with a possibility of program exit after 10 years for some lifetime designees. Stream D — Medical: a pathway available where medical conditions affect compliance, requiring assessments and adjustments.
Costs and obligations
The ignition interlock program is operated by private service providers approved by the Ontario Ministry of Transportation. Drivers are responsible for all costs: installation, removal, and monthly monitoring fees; calibration and service appointments (typically every 30 to 60 days); replacement device fees if the original is damaged; insurance increases — substantial after a DUI conviction; annual program costs typically run between $1,500 and $2,200 per year.
Conduct review and program extension
Failed start-up tests, missed service appointments, or attempts to circumvent the device trigger conduct reviews. The most common consequence is an automatic three-month extension of the program — sometimes longer for repeated incidents. Program completion is not just a function of time; it requires demonstrably clean device data.
How Mass Tsang helps with interlock issues
While the interlock program itself is administrative — handled by MTO and the program operators — its requirements flow directly from criminal sentencing. The DUI lawyers at Mass Tsang LLP consider interlock implications as part of the overall defence strategy. Avoiding a conviction, or negotiating an outcome that avoids interlock entirely (a careless driving plea on the right facts, for example), can save years of cost and inconvenience. For more on how the program operates, see our explainer on Ontario's ignition interlock program.
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