The aim of the presentation is to convey a methodological problem which is fairly well-known in the field of safety research, but which still lacks a proper solution. Accidents can be defined as the product of risk and exposure. Risk is generally expressed as a rate and a number of community, used rates are given in Figure 1. What do we need and use rates for? (Figure 2). We require rates when making comparisons, because the absolute numbers of fatalities or casualties are meaningless, or for monitoring trends over time. Some examples appear in Figures 3, 4. The use of rates, especially the travel-risk rate -- defined as casualties or fatalities per unit distance travelled, is very widespread. The problems associated with the use of this rate are described in Figures 5 and 6. (A)
Abstract