How to compare structurally different territories? The analysis of the evolution of road safety in a territory, and more particularly its mortality, is often delicate because the reduced number of accidents is subject to statistical uncertainties. Thus, accidents in the French departments and territories can vary significantly from one year to the next. The analyses most often cover periods of 3 to 5 years, either by looking at the number of victims or, in order to draw comparisons between territories, by using ratios. The most commonly used indicator is the ratio of the number of fatalities per population.