In September 2008 Nova Scotia's Alcohol Ignition Interlock Program was implemented. The overall objective of the Program was to improve road safety and reduce the number of road traffic crashes and fatalities that may occur due to impaired driving. This report describes the outcome evaluation of Nova Scotia's interlock program. The Traffic Injury Research Foundation (TIRF) conducted this outcome evaluation as part of a large-scale evaluation of this safety measure. The main objective of the outcome evaluation was to examine the impact of Nova Scotia's interlock program on participants and to help identify areas for improvement. More precisely, the goals of the outcome evaluation were: * To determine the effectiveness of the program to reduce drink driving when combined with counselling and other Addiction Services components provided to the offender; * To identify potential improvements to the program or implementation of the program; * To determine the use of the program, e.g., participation rates and attrition. The outcome evaluation addressed the following questions: 1. How many participants re-offend, and how often, while enrolled in the program? a. How many were caught and convicted of drink driving while in the program? How many were arrested but not convicted; how many were caught for other driving-related offences? b. How many self-reported that they drove while drinking (or within an hour of drinking) while in the program? 2. How many failed attempts were logged on the interlock device? a. What were the reasons for the failed attempts? b. What was the BAC level of these failed attempts? 3. How many times did participants use the interlock device while in the program? What was the mileage driven during participation? 4. How many drove a non-interlock vehicle while in the program (based on self-reported data and conviction data)? 5. How many re-offend after they finished the program? a. How many are caught and convicted of drinking and driving? b. How many self-reported that they drove while drinking (or within an hour of drinking)? 6. What is the impact of the various aspects of the program, for example, voluntary versus mandatory participation? 7. Have participants' knowledge, attitudes and behaviours changed as a result of the program and in what ways? The outcome evaluation also addressed interlock component-related research questions as discussed in the Process Evaluation Report (Robertson et al. 2010): 1. What is the distribution of participants in the program over time? 2. What is the attrition rate? 3. How do behavioural patterns among interlocked offenders change over time, more precisely with respect to blowing fails, violations and breath alcohol concentration (BAC) levels? 4. Is there a learning curve among participants on the device and does it change over time? 5. Is there a subpopulation that seems to be immune to the typical learning curve? 6. Is there a subpopulation that shows persistent and even deteriorating behaviour over time? Different types of data were used in this evaluation: conviction and crash records of individual participants, self-administered questionnaires to measure specific attitudes and behaviour, monthly counts of charges, convictions and crashes, and interlock logged events. For each type of experimental data (alcohol-related/interlock participants) except for the logged events, control data (no alcohol-related/no interlock participants) were also used to better support the findings. For the individual data analyses there were four different groups: two experimental interlock groups (voluntary and mandatory interlock offenders) and two control non-interlock groups (offenders that had the option to participate in the interlock program and declined, and a retrospective control group consisting of offenders that would have been mandated into an interlock program had one existed). The data were analysed using five different methods: 1. Several descriptive sub-analyses were conducted to investigate demographic characteristics and other features to determine whether and how much participants in the control groups differed from participants in the experimental groups with respect to a variety of dimensions. This provided important contextual information to ensure groups were sufficiently similar as well as to properly interpret results from any of the data analyses. 2. To provide insight into the effectiveness of the program in terms of recidivism, the longitudinal data from the experimental and control groups that were tracked over time were analysed using a variety of survival analysis techniques. These techniques allowed the comparison of time to recidivate or crash across participants in each of the groups. 3. To bolster the findings from the survival analyses and to make the conclusions more robust, time series analyses techniques were used to study monthly counts of crashes, convictions and charges. This made it possible to study any potential effect of the implementation of Nova Scotia's interlock program on these counts. 4. Changes in attitudes and opinions regarding the interlock program, drinking behaviour, and drink driving behaviour, as measured by surveys, were investigated separately using regression analysis. 5. Finally, the interlock data were also analysed without comparing these data to a control group to study behavioural trends of interlocked offenders. The descriptive analyses revealed that in general there were no significant differences between the respective experimental and control groups at the beginning of the study period, meaning that these groups were well-matched and highly similar. In terms of alcohol-related charges, the control-voluntary group exhibited a recidivism rate of 8.9% during the study period, while the interlock-voluntary and interlock-mandatory had recidivism rates of 0.9% and 3% respectively after the installation of the interlock device. The recidivism rates for the interlock groups increased to 1.9% (voluntary group) and 3.7% (mandatory group) after the devices were removed from the vehicle, but they were still smaller than the rate for the control-voluntary group. This means that interlock participants were less likely to recidivate, even once the device was removed. In terms of alcohol-related crashes the control-voluntary group exhibited a recidivism rate of 1.6% during the study period, while the interlock-voluntary and interlock-mandatory groups had a 0.6% and 0.8% rate respectively. These differences in terms of crashes were not statistically significant. Survival analysis. The results from the survival analyses demonstrated that: * The interlock program was associated with a positive impact on reducing the risk for alcohol-related convictions of participants while driving. * There seemed to be no difference between mandatory and voluntary participants in terms of risk for alcohol-related convictions. * With respect to crashes, the analysis did not show a statistically significant difference between any of the studied groups. Time series analysis. The results from the time series analyses suggested that: * There were no permanent effects on the number of alcohol-related charges and convictions in the province as a whole associated with the implementation of the program. * There were significant, albeit temporary effects in the first and seventh month after the program was implemented. These effects included: » a 13.32% decrease in the number of alcohol-related charges in September 2008; and, » a 9.93% decrease in the number of alcohol-related convictions in March 2009. * With respect to crashes, time series analyses suggested that: » At the 5% level of statistical significance, there were no significant effects associated with the implementation of the program on the number of alcohol-related crashes with fatal and serious injuries. » There was a permanent effect at the 10% level of significance that represented a decrease of 0.0025 in the number of alcohol-related crashes every month since June 2009 (tenth month after the beginning of the program). Statistically speaking, this represented a small decrease (one fatal or serious alcohol-related crash in approximately 33 years). This was not unexpected as, to date most studies have not yet been able to definitively demonstrate a positive impact on crashes due to the small sample sizes and lack of sufficient data. The small amount of data gathered from the questionnaires at exit and follow-up were insufficient to draw statistically significant conclusions and establish significant comparisons among groups with respect to changes in attitudes and opinions regarding the interlock program, drinking behaviour and drink driving behaviour. However, an interesting reported fact was that there was some evidence showing that a small proportion of interlock participants (in the mandatory group) drove a non-interlocked vehicle while in the program. This evidence should be considered in light of existing evidence about the alternative to interlocks, i.e., licence suspension, and which shows that many suspended drivers may drive anyway. While this finding may not be very surprising, it does speak to the importance of good monitoring of offenders while they are on the interlock, e.g., by tracking their mileage to help detect potential instances of driving non-interlocked vehicles. The analysis of the interlock data suggested that there were learning curves which illustrated that offenders were more likely to violate at the beginning of program participation, but over time these violations decreased as offenders supposedly learned about, or experienced the consequences of program violations and the nuances associated with the functioning of, and compliance with, devices. In general, the curves were steepest at the beginning of program participation until approximately month 10, indicating that the learning effect may decrease or stop after a period of time. There were no large differences between male and female participants but there were clear differences between mandatory and voluntary participants. Although both groups revealed a learning effect, the effect was more pronounced for voluntary participants. In addition, clear differences were found between participants with condition 37 (condition on driver’s license requiring a zero BAC) and participants without this condition. Although both groups revealed a learning effect, the effect was more pronounced for the participants without the condition. In conclusion, with respect to specific deterrence (i.e., referring to preventing recidivism) there was strong evidence to suggest that participation in the interlock program reduced the risk of alcohol related charges for the participants during the program. With respect to general deterrence (i.e., referring to a preventative effect on the entire population of drivers in Nova Scotia) there was a temporary decrease in the number of alcohol-related charges and convictions in the first and seventh month respectively following the implementation of the program. There was also some weaker evidence (i.e., at the 10% level of statistical significance) that there was a permanent decrease in the number of alcohol-related crashes with fatal and serious injuries every month since the tenth month after the beginning of the program. 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 are also some promising indications to suggest a decrease in the number of alcohol-related road traffic crashes and fatalities due to the interlock program, although this finding should be confirmed with more data (crash data was available only until 2010). In sum, 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. Several recommendations were formulated based on the evidence from this study. These recommendations are: * Continue the use of the interlock program in Nova Scotia; * Consider the systematic use of a performance-based exit in the interlock program; * Consider further strengthening of monitoring in the interlock program; * Consider focusing on levels of risk in relation to non-compliance; * Consider the continued monitoring of crash data. (Author/publisher)
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