The objective of this paper was to model the evolution of road safety as a function of motorization level. The authors completed a country-level as well as a time-dependent analysis focusing on countries for which data were available for a long period of time (1965 to 2009). For the statistical analysis, a function describing road safety trends (decline, turning, improvement) was proposed. Two coefficients in the model were estimated for each country and for each year, and their change over time is discussed. The results showed that the shape of the curve changed over time. In some countries, the decrease in the mortality rate became slower over time; however, a greater potential to improve road safety existed in other countries. Possible reasons for the general positive trends in road safety are the continuous improvement in engineering solutions (better infrastructure, safer cars) as well as road users who are better trained and skilled because of education and experience. In addition to the factors mentioned previously, the increased speed by which safety-related information and knowledge are disseminated contributes to the decrease in the differences in safety levels among countries.