The life cycle of the policy for preventing road accidents: an empirical example of the policy for reducing drunk driving crashes in Taipei

The purpose of this paper is to examine the temporal variation of the effect of preventive policy on reducing traffic accidents. The life cycle theory was introduced to describe the safety effect of the intervening policy over time. Poisson regression models with dummy-based and time-based specifications were used to evaluate the effect of an intervening policy over an observation period following its implementation. The policy of "Criminal sanction for drunk driving (CSFDD)" in Taipei city was evaluated as an empirical example to determine whether the temporal variation of safety effect happened to the CSFDD policy. The study results showed that alcohol consumption, arresting the drunk driving offenders, and the implementation of the CSFDD were the significant factors affecting the rate of occurrence of fatal accidents involving drunk driving. The effect of the CSFDD policy appeared to be a rapid initial response followed by a lower rate of decay. The existence of the life cycle implies that employing different observation periods following the implementation of a specific policy to evaluate its performance may obtain different effects. The results of this study are crucial for policy evaluation. The effects of safety policy should be carefully interpreted in order to avoid misleading the relevant authorities in coming to the wrong conclusions and as such make the wrong decisions.