Alcohol consumption among drivers subject to the Swiss license restriction of zero tolerance when driving.

The restriction of zero tolerance when driving (ZTD) imposed on drivers in Switzerland means that they may drink no alcohol at all before driving and basically consume only moderate amounts of alcohol at any other time. The Institute of Traffic Medicine in Zurich has recently started to confirm this moderate alcohol consumption by analyzing hair samples for ethyl glucuronide (EtG), a metabolite of ethanol. On the basis of the EtG results, this article looks at the alcohol consumption of drivers subject to ZTD restrictions and determines what recommendations can be made in relation to traffic safety. In particular, the behavior of people with alcohol dependence, who are known to have a reduced ability to control their drinking, is looked at in detail. Data from all 250 persons with ZTD restrictions, assessed at our Institute in 2010, were evaluated retrospectively. These drivers included 220 men and 30 women, all aged between 21 and 75 (mean age 41 ± 12 years). At the time of the expert review, 26 (10.4%) had no record of driving under the influence (DUI), 121 (48.4%) had one DUI offense, and the rest had 2 or more drunk driving offenses. The length of time for which ZTD is imposed is determined on an individual basis, depending on the history of use and course of events. EtG hair analysis of all 250 drivers with ZTD restrictions provided the following results: EtG assay was not performed in 16 cases (6%); 126 drivers (50%) did not have any detectable EtG (corresponding to total abstinence); 93 (37%) had an EtG concentration within the limits of social drinking; and the EtG concentration indicated excessive alcohol use by 15 people (6%). EtG was found to be in the range of excessive alcohol consumption in 3 (8%) of the drivers diagnosed as alcohol dependent. It was seen that the majority of those drivers who had previously abstained totally from alcohol continued to do so. None of the drivers with ZTD restrictions committed any drunk driving offenses in 2010. Imposing a ZTD restriction on individuals with moderate alcohol consumption or those with previous alcohol problems who have been stable for some time and now drink little or no alcohol is worthwhile. In addition, total abstinence from alcohol should be made a license restriction for those with serious alcohol dependence, due to the poor long-term prognosis.