Impaired driving is a threat to road-safety. In order to target preventive measures, predictive factors of recidivism are needed.

We aimed to study relapse rates in subjects who were detected with impaired driving between 2000 and 2006 and followed up to the end of 2009.

We aimed to analyse predictive factors of recidivism after impaired driving.

Follow-up of 1787 Swiss residents (89% men, mean age 35), in whom impaired driving was detected by laboratory analysis regarding alcohol, drugs and medications between 2000 and 2006. Criminal records (2009) were used to collect recidivism data. Mean observation time was 4.13 (SD 1.7) years. Kaplan Meier methodology and Cox analyses were conducted to analyse predictors of relapse.

Within the observation period, 605 relapses were detected (33.9%). Men oftener relapsed than women, young oftener relapsed than elderly people. Most relapses were detected after driving under the influence of alcohol with BACs within prescriptive limits (48.5%). Based on Kaplan-Meier analyses the probability of recidivism was about 20% after two years less time driving licence was abstracted. According to Cox analyses, relapses were predicted by driving under the influence of drugs and by previous irregularities.

The present study underlines the importance of socialdemographic characteristics and previous irregularities for recidivism in road traffic. In terms of driving under the influence of alcohol it points out the difficulty of prescriptive limits for BACs and discloses a high risk for recidivism in terms of driving under the influence of alcohol and drugs.