Author Sara Rahman
Published August 2022
Report Type Bureau Brief No. BB160
Subject Alcohol; Driving offences
Keywords logistic regression, alcohol, interlock program, driving offences



The Mandatory Alcohol Interlock Program (MAIP) was introduced in February 2015 for offenders convicted of refusing a breath test, high range drink driving and repeat drink driving. After serving an initial disqualification, offenders can choose to:
• drive with an interlock device in their vehicle, which requires a negative breath test to start the vehicle; or
• serve out the remainder of a 5 year automatic disqualification period.
We obtained a dataset of 10,209 interlock orders from Transport for NSW that had an initial disqualification period ending on or before 20 April 2019 and linked these with the NSW Bureau of Crime Statistics and Research’s Re-offending Database (ROD). We used logistic regression to examine factors associated with: a) starting MAIP (for the entire sample); and b) completing MAIP (using 2,860 interlock orders where a person had installed an interlock device and could have completed the program by 20 April 2019). We measured the performance of our models using the Area Under the Curve (AUC).

Key findings

Interlock devices were installed by offenders in 68.7% of orders in our sample. Offenders were less likely to start MAIP if they were:
• already disqualified at the time of the offence (15 percentage points less likely to start);
• aged 55 years and above (20 percentage points less likely to start the program than 18-24 year olds);
• Aboriginal (12 percentage points less likely than non-Aboriginal offenders and 15 percentage points compared to those with unknown Aboriginality); or
• sentenced to imprisonment at the index contact (15 percentage points less likely to start).
Most offenders who started MAIP completed the program (91%).


Criminal and operational factors can predict interlock installation moderately well. Given that most of those who commence the interlock program complete it, improving commencement rates should be prioritised.