Part 2. Beyond single-outcome models: Decompositions of aggregate and disaggregate road safety risk

Using these four critical dimensions, we summarize both aggregate and disaggregate model developments, classifying them notably with respect to number of risk outcome levels addressed, severity categories accounted for, mathematical form of their variables and number of classes of explanatory variables put to contribution. For aggregate models, we document evolution from early ones explaining a single damage category for one region to the latest explaining multiple damage categories for many regions, not forgetting intermediate cases. With respect to the disaggregate models, in addition to providing a classification with respect to the same four dimensions, we raise the specific problems of aggregation from individual to population values without which discrete analysis remains of limited relevance, giving disproportionate attention to the landmark by Bolduc et al., available for the first time in English in this issue.