This study investigated the efficacy of mandatory seatbelt legislation on traffic injuries and intensity of road traffic injuries (RTIs). We carried out a before-after interventional study. Data regarding road traffic accidents and injuries one year before and one and two years after the implementation of mandatory seatbelt legislation were obtained from the traffic police database. Traffic accident mortality was 13.0% of all RTIs during the year prior to implementation. This decreased to 9.7% and 11.4% during the first and second years after implementation, respectively (p< 0.001). The mortality rate was not consistent for seatbelt use since there was a slight increase in the mortality rate in second year after implementation of mandatory seatbelt use although this level was lower than the pre-implementation rate. Our findings suggest mandatory seatbelt use reduces the intensity of RTIs and reduces the crude number of RTIs.