Although Zone 30 is being rapidly implemented in Japan to improve pedestrian traffic safety, its impact on the number of traffic accidents over time and its relation to land use is still unclear. This study analyzes changes in the number of traffic accidents in Zone 30 areas before and after implementation. To this end, a time-series analysis of traffic accidents in 10 Japanese prefectures was conducted. The results show that the policy reduces the number of Killed or Seriously Injured (KSI) traffic accidents in a 2-year before-and-after comparison. The study also investigated the relationship between the policy’s impact on an area and its land use. The results indicate that the type of land use in an area affects the change in the number of traffic accidents following the implementation. These findings suggest that observing the target area and understanding its characteristics, such as land use, are necessary for effective regulation.