The purpose of quantitative accident analyses is often to show relationships between accidents or accident risk (rate) and different road or external factors. These are often difficult to explain at the macro level, but might serve as a basis for hypotheses about different aspects of driver behaviour. Two examples are investigations of accident rate variation with: a) pavement surface wear, and b) the amount of rainfall. One shows that traffic safety is higher on roads with worn surfaces. The other indicates that although heavy rainfall increases the accident risk, small amounts of rain might actually decrease the accident rate compared to dry conditions. These results are not satisfactorily explained by differences in speed. Most likely there are other aspects of driver behaviour that are important as well, such as - those related to driver vision and behaviour.
Abstract