An evaluation of Nova Scotia’s alcohol ignition interlock program

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Highlights

  • Nova Scotia’s alcohol ignition interlock program was evaluated.

  • Methods used include survival, time series and logistic regression analysis.

  • Data show a reduction in recidivism of up to 90%.

  • There was a significant decrease in alcohol-related serious and fatal crashes.

  • Program violations decreased over time suggesting learning behavior.

Abstract

Alcohol ignition interlock programs for offenders aim to reduce recidivism among convicted drink drivers. This study presents an evaluation of Nova Scotia’s interlock program implemented in 2008 in order to assess its effectiveness to reduce impaired driving and to help identify areas for improvement. Data used include conviction and crash records of individual participants; provincial monthly counts of alcohol-related charges, convictions and fatal and serious crashes; and interlock logged events. Methods used include descriptive statistics, survival analysis, time series and logistic regression analysis. With respect to specific deterrence (i.e., preventing recidivism) there was a 90% reduction in recidivism among voluntary participants since participation in the interlock program and a 79% reduction after these participants exited from the program. With respect to general deterrence (i.e., referring to a preventative effect on the entire population of drivers in Nova Scotia) there were temporary decreases in the numbers of alcohol-related charges (13.32%) and convictions (9.93%) and a small significant decrease in the number of fatal and serious injury alcohol-related crashes, following the implementation of the program. The evidence suggests the interlock program was better at preventing harm due to alcohol-impaired driving than the alternative of not using the interlock program. Recommendations were formulated supporting the continuation of the interlock program in Nova Scotia.

Introduction

An alcohol interlock device is meant to prevent drivers from starting their vehicles if they have been drinking. The device requires the driver to blow into a breath alcohol testing device connected to the starter or other on-board computer system in order to start the vehicle and also requires repeated breath tests while the vehicle is in use to ensure the driver continues to remain sober.

Research has demonstrated that alcohol ignition interlocks can be very effective to combat alcohol-impaired driving (e.g., Marques et al., 2010, Rauch et al., 2011, Zador et al., 2011). A systematic review of 15 scientific studies conducted by the Centers for Disease Control and Prevention (CDC) found that while interlocks were installed, the re-arrest rate of offenders decreased by 67% compared to groups that did not have the device installed (Elder et al., 2011). A meta-analysis of interlock program evaluations found an average reduction of recidivism of 64% (Willis et al., 2004). Regarding the impact of interlocks on crashes, the systematic review of the literature conducted for the CDC (Elder et al., 2011) revealed limited evidence that alcohol-related crashes decrease while the interlock device is installed. McCartt et al. (2013) reported an 8.3% reduction in single-vehicle late-night crash risk (a proxy for alcohol-related crashes) associated to a change in the law in Washington State in 2004 that extended the interlock order requirement to first time offenders with blood alcohol concentrations (BACs) below 0.15%. More recently, Kaufman and Wiebe (2016) investigated the impact of state ignition interlock laws on alcohol-involved crash deaths in the U.S. using data from 1999 to 2013 and found that requiring ignition interlocks for all drunk-driving convictions was associated with 15% fewer alcohol-involved crash deaths, compared to states with less-stringent requirements.

Compliance with the interlock device tends to be low at the beginning of Alcohol Ignition Interlock Program (AIIP) participation when offenders often try to circumvent the alcohol interlock or fail to provide the required level for the breath test. However, research indicates that the non-compliance decreases over time as the offender becomes more used to the device and gains an understanding of the sophisticated technology involved and the futility of trying to circumvent the device (Vanlaar et al., 2010, Vanlaar et al., 2013). Zador et al. (2011) found that non-compliance could be reduced through close supervision, installation of a data logger, the provision of thorough interlock training at the time of device installation, and the provision of information to offenders regarding the consequences of circumvention, refusals, and failed breath tests.

Research is ongoing to identify the effective features of AIIPs. A recent study of AIIPs across 28 states in the U.S. shows that requirements which cover more types of offenders, especially first-time offenders, were strongly associated with interlock use increases (Casanova-Powell et al., 2015). The same study found that other key features (monitoring, coordination, uniformity and education) were moderately to strongly related (correlations larger than 0.3) to higher interlock-in-use rates (interlocks in use per 10,000 population, per 100 Driving While Impaired or DWI arrests, and per DWI fatality). Other collaborative initiatives that involve researchers, practitioners and government agencies are beginning to identify much-needed guidelines for programs based on existing knowledge and new experiences (National Highway Traffic Safety Administration, 2013).

In September 2008, Nova Scotia's AIIP was implemented with the objective to improve road safety and reduce the number of road traffic crashes and fatalities that may occur due to alcohol-impaired driving. Prior to enrolling in the AIIP, the DWI offender must register in the Alcohol Rehabilitation Program by Addiction Services of Nova Scotia. In this program, participants attend two days of DWI education in a group setting, complete a bio-psycho-social assessment, complete the Research Institute on Addictions Self-Inventory (RIASI; see Nochajski, 2002) and obtain a risk rating. Nova Scotia's AIIP involves both voluntary and mandatory components. It is voluntary for first-time offenders convicted once of drink driving or of refusing a breathalyzer test, and who were also deemed to be a ‘low' or ‘medium' risk as per Addiction Services’ bio-psycho-social assessment. Mandatory participants are those who are repeat offenders or who are deemed to be a ‘high' risk according to Addiction Services. After entering the program, participants must have an alcohol interlock device installed on their vehicle(s). They then receive an interlock licence and must participate in ongoing rehabilitation counseling sessions throughout the interlock period. During the sessions, a specific treatment plan is tailored to the individual needs of the offender, and a review is conducted of the data log from the interlock device.

In 2010 a process evaluation was finalized to obtain an understanding about how Nova Scotia's AIIP was developed and implemented (Robertson et al., 2010). Overall, the results revealed that the implementation of the AIIP in Nova Scotia proceeded according to the plan. This study presents the results of the outcome evaluation of Nova Scotia’s AIIP. Specifically, the outcome evaluation was conducted to determine the use of the program, its effectiveness to reduce drink driving when combined with counselling and other services provided to the offender, and to identify potential improvements to the program. The results presented here augment the results previously reported (Vanlaar et al., 2014) with an additional year of crash data.

Section snippets

Data

Different types of data were used in this evaluation. First, different groups were formed: two experimental interlock groups (929 voluntary and mandatory interlock offenders) and a control group (326 non-interlock offenders). The interlock participants were recruited among those who entered in the AIIP from March 2010 to December 2012. The non-interlock participants were recruited during the same period among offenders that had the option to participate in the interlock program but declined and

Descriptive analysis

Table 1 shows the percentage of participants in each group (interlock-mandatory, interlock-voluntary and control) that had alcohol-related convictions and crashes during the tracking periods. The tracking period for the participants in the control group was defined from their inclusion date in the study until the end of June 2014. The tracking periods for the interlock groups were: a) since installation of device and b) since removal of device, until the end of June 2014. This allowed examining

Discussion

In terms of specific deterrence with respect to alcohol-related convictions, the control group exhibited a recidivism rate of 8.9% during the study period, while the interlock-voluntary and interlock-mandatory groups had a 0.9% and 3% recidivism rate respectively after the installation of the interlock device. The recidivism rate for the interlock groups increased to 1.9% (voluntary group) and 3.7% (mandatory group) after the device was removed from the vehicle, but they were still

Conclusions

When considering all the evidence combined, it can be argued that the implementation of the interlock program had a positive impact on road safety in Nova Scotia and that it reduced the level of drink driving recidivism in the province. There were also some promising indications to suggest a decrease in the number of alcohol-related fatal and serious crashes due to the AIIP, although this finding should be confirmed with more data (crash data were available only until 2011) to see if there is

Acknowledgements

Funding for this work was provided by the Nova Scotia Department of Transportation and Infrastructure Renewal and the Traffic Injury Research Foundation.

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