Most appropriate exposure measures

The most appropriate measures of exposure appear to be vehicle- and passenger-kilometres of travel, because they are closer to the theoretical concept of exposure and can be available, in theory, to a satisfactory level of detail.

The number of vehicle kilometres is probably the most often preferred exposure measure. One important practical advantage of the use of vehicle kilometres (over road length, fuel consumption, driver population and vehicle fleet) is that, in theory, it may be available to a significant level of desegregation: time, vehicle type, road type, or driver characteristics. None of the other exposure measures can usually allow for this level of detail. For that reason it is probably the best measure (alongside person kilometres) to capture the regional and temporal variations in the accident process. It is also useful for analyses on specific features of the road safety problem.

The number of person kilometres is probably the second most often preferred exposure measure. Its application is mostly geared towards casualties' counts. However, due to the fact that the person- and vehicle-kilometres estimates are often obtained though the same data source (e.g. travel surveys, traffic counts etc.) person kilometres can be derived from vehicle kilometres and vice versa. Moreover, driver kilometres, which are sometimes used to substitute vehicle kilometres, can often be derived from person kilometres.

A first classification of the EU member states on availability, compatibility and usability of exposure and risk data.