Road safety problems can be approached by `top down' methods which concentrate on symptoms and describe accidents in terms of variables representing the road traffic system, or by `bottom up' methods which make use of explanatory variables such as friction, road user behaviour etc. A case study is a hybrid of these two approaches since it concentrates on accidents which have actually occurred but analyses these in terms of accident generation models. The case study method makes possible the collection of a large body of data from a small number of accidents. Case studies have the character of interdisciplinary in-depth studies. In studies of conflicts between vehicles and cyclists at road junctions, the method junctions, the method concentrates on the pre-crash phase. The results of a case study relate to only one accident and cannot be generalised. Further investigation must be made on the basis of the case study to find whether there are any factors which are of general significance. For comments on this paper, see C 6521 and C 6522.
Abstract