Detecting intoxicated drivers in Germany -- estimating the effectiveness of police tests

The most important prerequisite for deterring people from driving while intoxicated is to persuade them of the likelihood of being detected by the police. Detection requires the police (1) to stop intoxicated drivers and (2) to detect the intoxication. The latter is not a simple task in Germany as the police is only allowed to obtain a breath sample when indications of an intoxication are present. The paper estimates the effectiveness of police tests in detecting intoxicated driving by comparing data from the German Roadside Survey and the Unterfranken Accident Study to a study of usual police routine and to official accident statistics. Both the German Roadside Survey and the Unterfranken Accident study were conducted in such a way that breath alcohol testing was carried out for nearly every driver, thus giving an estimate of the number of intoxicated trips and accidents in Germany. Comparing these numbers to the intoxicated trips and accidents detected by the police allows a detailed analysis of different components of detection. From those, suggestions are given for increasing the effectiveness of police work.