Any time there are reductions in accidents, advocates of any particular position are quick to claim that it is their "effect" that has improved safety performance. The work in this paper focuses on interpreting a traffic system's performance with respect to a specifictype of accident by attributing a change in the number of accidentsto the relative contribution of three effects: the activity effect, the safety content effect, and the structure effect. A method is developed and applied to the data sets of pedestrian fatalities that occurred in Greece during the period of 1965-1989. The relative contribution of the effects as well as the pattern changes turn out to have a decisive influence. The possible uses and extensions of the method are also discussed. (A)
Abstract