Crash causation, countermeasures, and policy - Editorial.

This editorial is both an introduction to the papers that make up this special issue (on the Relationship between Crash Causation, Countermeasures, and Policy) and an attempt at drawing conclusions. To assist the reader, we begin with a brief description of the subject matter of each paper. As expected, the authors tackle different aspects of this general topic and often differ in their conclusions.

Even correctly specified and well-estimated regression models can mislead.

It should be possible to draw causal conclusions from happenstance data. However, there are many well-known reasons for doubting the causal interpretation of single equation regression models based on such data. Still, hope springs eternal.

Crash causation and prevention.

Knowledge of crash causes is important because it directs the mind to the consideration of potential prevention actions and because knowledge of the frequency with which various causes arise in crashes is necessary for determining the promise of potential prevention actions. Clinical crash causation studies consistently found that in the majority of crashes the road user was the sole cause and that in almost all crashes the road user was one of the causes. This is a 'quasi-finding' which provides false respectability to a style of road safety management that makes the road-user the primary target of prevention actions.

Engineering judgment and road safety.

Decisions that highway and traffic engineers make significantly affect the safety of road users. The documents that guide highway and traffic engineering practice suggest that many of these decisions be made by 'engineering judgment'. One would like this judgment to be informed by evidence-based anticipation of their likely safety consequences and by a professional ability to balance safety against mobility and other dimensions of 'utility'.