Traffic Law

Mandatory Interlock

Mandatory Interlock Orders are made by Courts when sentencing offenders in certain circumstances for drink driving offences. 

What are the effects of a Mandatory Interlock Order?

When a Mandatory Interlock Order is made, a driver receives a period of disqualification from driving or obtaining a driver's licence. The disqualification period is dependent on what type of drink driving offence the person is convicted of and whether it is a second or subsequent offence. 

For offences where an Interlock Order is made, the driver must then obtain an Interlock licence and maintain that licence for a period of time. During the "Interlock Period", the driver is able to only drive a car fitted with the Interlock device and is required to pay for the device to be installed on a vehicle and continue to pay a regular maintenance fee for the duration of the Interlock period.

Should the driver not obtain an Interlock licence, the driver remains disqualified for a period of up to 5 years unless and until the Interlock licence is obtained and maintained for the duration of the Interlock period.

What is an "Interlock device"?

An Interlock device is an electronic device that is fitted to a vehicle and linked to the vehicle's ignition. Before starting the vehicle the driver is required to provide sample of his or her breath. The device then analyses the breath sample and should alcohol be detected, then the vehicle will not start. Even after successfully starting the vehicle, the device requires random samples to be given during the journey where again, a sample of the driver's breath is analysed for the presence of alcohol. Further, a photo is taken of the driver every time the driver provides a sample. The device logs and stores the information and it is therefore designed to ensure that drivers are not able to "cheat" the device by having a passenger provide the necessary breath sample, when prompted.

When is an Interlock Order made?

An Interlock order must be made where a driver has committed any high range drink driving offence (whether a first offence or otherwise) and any other drink driving offence that is considered a second or subsequent offence. The below table shows some of the offences for which an Interlock Order is made along with the disqualification periods and minimum Interlock periods. It must be remembered that a Court has the discretion to increase the Interlock period beyond the minimum.

Mandatory Disqualifications and Interlock Periods



Minimum Interlock Period




2nd Low Range, Novice Range or Special Range

1 month

3 months

12 months

2nd Mid Range or Drive Under the Influence

6 months

9 months

24 months

1st High Range or Refuse Breath Analysis 

9 months

12 months

48 months

2nd High Range or Refuse Breath Analysis 

9 months

12 months

48 months

Are there exemptions?

At the time of sentencing, the starting position is that the Interlock Order is mandatory and therefore, must be made. However, if the offender can satisfy the Court that essentially, the offender does not own or have access to a vehicle, or the offender, due to a medical condition, will be unable to comply with the Interlock requirements, then the Court is to make an Interlock Exemption Order. If an exemption order is made, then the offender is then to be dealt with differently, where longer minimum disqualification periods are imposed and no Interlock order is made.

The above is an outline of how and when Mandatory Interlock orders are made and the effect thereof. You can find more information on the Mandatory Interlock scheme at the Roads and Maritime (RMS) website.

If you have been charged with a drink driving offence and require legal assistance, then we invite you to contact one of our experts at  your nearest Prime Lawyers office.

Our offices are located at our Sydney, Parramatta, Chatswood, Sutherland and Wollongong offices.

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