Safety Performance Indicator for alcohol in road accidents--international comparison, validity and data quality.

Safety Performance Indicators, SPIs, are developed for various areas within road safety such as speed, car occupant protection, alcohol and drugs, vehicle safety, etc. SPIs can be used to indicate the road safety situation and to compare road safety performance between countries and over time and to understand the process leading to accidents, helping to select the measures to reduce them. This article describes an alcohol SPI defined as the percentage of fatalities resulting from accidents involving at least one driver impaired by alcohol. The calculation of the alcohol SPI for 26 European countries shows that the SPI varies from 4.4% in Bulgaria to 72.2% in Italy. These results raise the question if the results reflect the real situation or if there is a methodological explanation. To answer this question three different studies were carried out: comparison with other alcohol SPIs, in-depth studies of data quality in seven selected countries, and a study of correlations between the SPI and influencing factors. These studies indicate clearly that there is a need to improve quality of the data used for the alcohol SPI. Most importantly, the total number of drivers involved in fatal accidents, the number tested for alcohol and the number not tested, should be reported, in addition to the number of alcohol positive and negative drivers among those tested. Until these improvements are made, the validity of this SPI seems poor and comparison of the alcohol SPI results across countries should be made with caution.