Most of the studies have used interrupted time series analytical methods, although the designs vary in formality and sophistication. The research on the subject of drunk driving is favored by relatively good measures, such as fatal crashes, and the possibility of relatively strong quasi-experimental designs, since the independent variable changes abruptly at a single point in time. The Scandinavian-type laws adopted in Scandinavia, Great Britain, France, the Netherlands, Canada, the United States, New Zealand, and Australia prohibit driving with a blood alcohol concentration above an arbitrary standard. Breath and blood tests determine the blood alcohol concentration. The laws also provide for relatively severe punishments, such as loss of license and prison sentences. Some countries have reinforced the laws through enforcement campaigns accompanied by publicity. Some jurisdictions also substantially increased the penalties for alcohol-impaired driving without accompanying increases in enforcement. These activities have produced important deterrent effects usually have proved to be temporary. The interventions were successful because they temporarily increased the perceived certainty of punishment. Interrupted time-series analysis is valuable for studying drunk driving laws and holds potential for the study of many other types of legal innovations. Figures and a list of 30 references are provided.