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.

研究事故原因的信念是，通过查找原因，可以通过消除或控制其原因来预防事故。因此，传统上被视为导致事故发生的风险因素只有在可以通过一项或多项道路安全措施加以改变的情况下才能被视为原因。如果通过实施一项或多项影响风险因素的道路安全措施可以改变风险因素与事故的关系，那么风险因素就是原因。因此，本来可以采取道路安全措施来改变被确定为导致事故的风险因素，但没有采取的措施，也是事故的原因。许多传统上被认为是事故风险因素的人为因素，如年龄、性别、驾驶经验、期望或不自觉的注意力不集中，并不是事故的原因，因为它们无法通过任何现实的道路安全措施来改变。无法改变的（不可能有所不同）并不是原因。无论是在案例研究还是在统计分析中，都可以确定一组诱发或促成事故的因素何时完成。可以实施的道路安全措施清单仅受我们的创造力和想象力的限制，因此永远不会完整。