Differences between groups of drivers: Offences contrasted with crashes

If an intervention can be shown to affect the number of driving offences, is this also evidence that it has an effect on road crashes? We summarise two recent studies in which we found a difference between groups in respect of driving offences but not in respect of crashes. One study focused on the method of obtaining a driving licence, the other concerned participation in a brief intervention program for young offending drivers. Further, the literature reveals other examples of different effects on offences and crashes. One possible explanation is that there is a closer link between the behaviours targeted by the intervention and being caught offending than between those same behaviours and being involved in a crash. Unfortunately, the question remains open as to whether there is an effect on crashes that is in the same direction as the effect on offences but smaller, or whether there is no effect on crashes because the behaviours that differ between the groups are not relevant to crashes