In Autumn 1991, experts at a workshop in Padova, Italy, discussed methodological issues in drugs and driving. The primary purpose was to review three major papers that would form the core of a manual on drugs and driving methodology, to encourage consistency and standardisation between countries and research institutes. This paper summarises the chapter of the manual on epidemiological methods in the study of drugs and driving. It aims to: (1) identify key methodological problems in surveys designed to determine the influence and role of drugs in road crashes; (2) recommend standardised methods of data capture and analysis to overcome, or at least minimise, these problems, thus increasing the comparability of findings from studies worldwide. The paper offers a guide rather than a cookbook. Most of the general methodological issues come under sample selection and data collection. The two major types of surveys used are surveys of drug use in the general population and in the driving population. Surveys of arrested drivers and clinical populations are important, as they represent high-risk groups. Surveys of fatally injured drivers require methodological consistency, to allow meaningful comparisons. Relevant aspects include: (1) sample characteristics; (2) drug determinations; (3) reporting results; and (4) the interpretation of findings.
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