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Abstract
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BACKGROUND
The Mandatory Alcohol Interlock Program (MAIP) was introduced in February 2015 and applies to 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.
To evaluate the impact of the program, we used a dataset of 98,501 proven drink driving and refuse to provide a breath sample offences committed between 1 February 2012 and 30 April 2018, linked to Transport for NSW datasets on MAIP orders and crashes. We compared outcomes for first-time offenders who took up MAIP and who recorded a Blood Alcohol Concentration (BAC) just above the 0.15 threshold, with outcomes for first-time offenders just below the threshold who were likely to have taken the program up were it available. To estimate the program's overall impact, we also compared outcomes for offenders who committed MAIP-eligible offences with offenders who committed first time mid-, low- or special-range drink driving offences, before and after MAIP was introduced.
AIM
To evaluate the impact of the first phase of the Mandatory Alcohol Interlock Program (MAIP), introduced in NSW in February 2015, on repeat drink-driving, driving while disqualified, traffic infringements, and crash outcomes.
METHOD
We use a dataset of 98,501 observations involving offenders with a proven 'exceed the prescribed concentration of alcohol' (PCA) offence or a 'refuse to provide a breath sample' offence finalised in a NSW court between 1 June 2012 and 30 April 2018. We identify the impact of taking up an alcohol interlock on reoffending and road crashes using a regression discontinuity design. This analysis compares outcomes for first-time PCA offenders in a small bandwidth on either side of the high range blood alcohol concentration (BAC) threshold of.15. We also estimate the overall impact of the introduction of MAIP on drink driving and road crashes using a difference-in-differences approach. This compares outcomes for eligible and ineligible offenders before and after the introduction of the program. We implement a range of robustness checks and analyse outcomes for various groups of offenders, including those receiving different interlock periods, and those with different demographic characteristics and criminal histories.
RESULTS
MAIP reduced the likelihood of drink driving during the interlock period for first-time high range PCA offenders who start the program by 11 percentage points (p.p.; a reduction of 86%) compared to mid range offenders just below the high range PCA threshold. We also observe reductions in PCA offending within 36 months of finalisation (of 3.4 p.p.; 43%) and within 60 months of finalisation (of 6.0 p.p.; 43%) among all eligible offenders compared to offenders committing eligible offences before the program's introduction. The program reduces traffic infringements committed after court finalisation, but these effects are concentrated among repeat low range PCA drink drivers. We do not find significant effects of the program on reducing the likelihood of involvement in an alcohol-related crash nor on crashes resulting in injuries and fatalities. The reductions in PCA offending are particularly large for offenders convicted of the most severe offences (i.e., repeat high range drink driving and repeat refuse to provide a breath sample offenders), those residing in disadvantaged areas, and to a lesser extent, those residing outside major cities.
CONCLUSION
Alcohol interlocks significantly reduce drink driving while interlocks are active and (to a modest extent) following their removal.
Available:
http://www.bocsar.nsw.gov.au/Publications/CJB/CJB251-Report-Effectiveness-of-MAIP-in-reducing-drink-driving.pdf
See also Appendix:
https://www.bocsar.nsw.gov.au/Publication%20Supporting%20Documents/CJB/CJB251-Appendix-Effectiveness-of-MAIP-in-reducing-drink-driving.pdf
Language: en |