On the Radar: an evaluation of a police letter campaign among prolific traffic offenders in the Netherlands

This study examines the effectiveness of a police intervention aimed at reducing recidivism among prolific traffic offenders in the Netherlands. Selected offenders received a formal letter intended to raise awareness of driving behavior and deter future violations through increased perceived surveillance. The letter incorporated elements of focused deterrence and procedural justice theory. The evaluation consisted of two phases. The first phase (2024) used a quasi-experimental difference-in-differences design, comparing letter recipients with a comparable group of offenders who did not receive the letter. The second phase (2025) employed an RCT, with eligible offenders randomly assigned to a treatment (receiving the letter) or a control group (no letter). A negative binomial regression model was used to analyze the second phase. Recidivism was measured for nine months in each phase. Both phases showed no statistically significant differences between treatment and control groups, indicating that the intervention did not reduce recidivism.