Alternative understandings of risk and exposure

The report discusses the probability theoretical foundation for calculating risk in traffic as well as measure of exposure, which is used in road safety research. The report argues that although the events that could result in an accident is theoretically the best exposure measure, there is a risk in some cases to control away important risk factors that create accidents with such a measure of exposure. The report argues that one should choose a measure of exposure that captures traffic participation, yet not very strongly correlated with accidents. Similarly, it is argued that when comparing risk among groups one should be careful when controlling for various risk factors influencing these differences. The report shows estimates of risk with time and distance as a measure of exposure and concludes that the traditional measure of exposure - distance - in many cases is a preferred measure of exposure in risk calculations.