What is an Alcohol Interlock?

An alcohol interlock is a device that will not start your vehicle if it detects that you have had a drink. This prevents you from driving if you're over the legal blood alcohol limit, and is put in place to deter drivers from drinking and driving and to keep the roads safer.

You will need to have an alcohol interlock fitted before you can get your licence back after a drink driving conviction and/or disqualification from your licence. If you don't, the Magistrate Judge may not give your licence back. You can appeal against this if you're successful, but there is no guarantee that the judge will use their discretion and remove your licence without the interlock.

There are a number of factors that the Magistrate Judge will consider when deciding if to allow your licence to be returned without an interlock. They will take into account elements such as how much you drink, how you drink and any incidents that you've had in the past.

Currently, the law requires only first and repeat offenders who are above the legal blood alcohol limit to have an interlock device fitted for between six months and four years. However, this could change under a new plan being proposed by the Victorian State Government.

The device uses a fuel cell sensor which detects the amount of alcohol in your breath. The alcohol is oxidised at a catalytic electrode surface to generate an electric current. This current is then measured and converted to an alcohol equivalent reading.

This data is then downloaded from the device supplier on a regular basis and used by VicRoads to decide whether your licence is eligible for an interlock condition. The data is also used to monitor the effectiveness of the program and to identify those who are a high risk of reoffending.

There is evidence that alcohol ignition interlock programmes reduce recidivism (drinking and driving again) in repeat offenders while the device is in use. This is supported by the results of nine non-randomised controlled trials compared to controls. In two of these, the interlock participants had lower recidivism rates than the controls and in six of these, the difference was statistically significant.

A number of questions remain about the effectiveness of this intervention including whether different support services provided during and after use of an interlock device affect recidivism. Further research is needed to address these issues, and to determine if the interlock programme is a successful tool for reducing repeat drunken driving.

In addition, it is unclear whether a device that records failed interlock BAC tests can predict future recidivism. There are many other issues around the use of alcohol ignition interlock programmes, so it is important to continue to review them and investigate their potential impact on a range of areas.

This is particularly important if drink driving related accidents remain a serious problem in Victoria. If a driver who is not using an interlock continues to drive under the influence of alcohol, this can lead to an increase in road fatalities. This can cause an estimated loss of over $1 billion to the community every year.