Risk factors as causes of accidents: Criterion of causality, logical structure of relationship to accidents and completeness of explanations

The causes of accidents are studied in the belief that by finding causes, accidents can be prevented by removing or controlling their causes. It follows that the risk factors that have traditionally been regarded as contributing to accidents can only be regarded as causes if it is possible to alter them by means of one or more road safety measures. Risk factors are causes if their relationship to accidents can be changed by implementing one or more road safety measures influencing the risk factors. Hence, road safety measures that could have been implemented to change risk factors identified as contributing to an accident, but have not, are also causes of accidents. Many of the human factors that have traditionally been identified as risk factors for accidents, like age, gender, driving experience, expectations or involuntary inattention are not causes of accidents, because they cannot be changed by means of any realistic road safety measure. What cannot be changed (could not have been different) is not a cause. It is possible, both in case studies and in statistical analyses, to determine when a set of factors precipitating or contributing to accidents is complete. A list of road safety measures that could have been implemented is only limited by our creativity and imagination and will therefore never be complete.