To establish the biggest problems we analyse existing databases with crash data and establish which problems occur most frequently. For example, it could be the many casualties among car occupants or among pedestrians in case of truck collisions. However, we might decide not to consider absolute casualty numbers but to compare the number of casualties to the distance travelled by specific groups, to establish the traffic risk. Then it may turn out, for instance, that young and novice drivers run a relatively high risk. We might also decide not to analyse a specific period but to consider trends over time. The risks for motorcyclists, cyclists and pedestrians in the UK are much higher than in both other countries.