Evaluating the Effectiveness of an Alcohol Ignition Interlock Program

This thesis presents the first comprehensive evaluation of the Dutch Alcohol Ignition Interlock Program (DAIIP), introduced in 2011 to reduce driving under the influence (DUI) and alcohol-related traffic casualties. Alcohol ignition interlocks are internationally used as part of Alcohol Ignition Interlock Programs (AIIPs) and prevent impaired driving by requiring a negative breath test before a vehicle can start. The Dutch DAIIP targeted moderately severe DUI offenders and combined mandatory interlock installation for a minimum of two years with an intensive Monitoring & Support program, including breath-test monitoring, individualized feedback, and educational components aimed at sustained behavioral change. Despite its promising design, the DAIIP was discontinued in 2016 due to legal concerns related to proportionality and the principle of ne bis in idem, rather than because of demonstrated ineffectiveness. Consequently, the program was terminated before its impact could be adequately evaluated, despite the continued prevalence of alcohol-related traffic incidents and growing political and public support for its reinstatement. Against this background, the central aim of this thesis was to assess the effectiveness of the DAIIP in reducing DUI recidivism and to provide empirical evidence to support evidence-informed policymaking. Four research questions were central to the study: (1) the extent to which judicial records can be used to study DUI recidivism; (2) the effectiveness of the DAIIP in reducing short-term recidivism during interlock use; (3) its effectiveness in reducing long-term recidivism after program completion; and (4) whether effects vary across offender subgroups. Methodologically, the thesis used judicial data from the Dutch Offenders Index, supplemented with licensing authority data. Following an initial assessment of the strengths and limitations of judicial records, three large-scale, population-level retrospective cohort studies were conducted using rigorous quasi-experimental designs. Although underreporting is a major issue, judicial data can still be valuable for criminological research. These records provide a comprehensive view of offenders formally held accountable for their risky behavior and can be used in the context of comparative recidivism research to evaluate the effectiveness of measures designed to prevent repeat offenses among known offenders. The evaluation of short-term effects showed that DUI recidivism among DAIIP participants during the interlock period was extremely rare, whereas recidivism among offenders who opted for a five-year license suspension was approximately ten times higher. This highlights the strong incapacitating effect of the interlock device and aligns with international evidence showing that technological prevention is more effective than sanctions relying on voluntary compliance. Importantly, the thesis also found evidence of sustained behavioral change. DAIIP participants exhibited significantly lower long-term DUI recidivism rates than comparable offenders who received only criminal sanctions, corresponding to a relative reduction of more than 50%. This suggests that the combination of technological enforcement and the Monitoring & Support program contributed not only to short-term prevention but also to lasting behavioral change, contrasting with earlier studies reporting limited post-program effects. Subgroup analyses indicated that the DAIIP was effective across most offender groups, including men and women, novice and experienced drivers, and individuals with varying criminal histories. However, no significant benefits were observed for early-onset offenders whose first justice system contact occurred before age 16, suggesting that this high-risk group may require more comprehensive interventions beyond alcohol- and traffic-focused measures. In conclusion, this thesis provides robust empirical evidence that the DAIIP effectively reduces DUI recidivism during and after participation, though not uniformly across all subgroups. It strengthens the program’s legitimacy, contributes to the international AIIP literature, and offers policy recommendations to address proportionality concerns while preserving the core elements essential to improving road safety in the Netherlands.