This paper describes the accident study on the Marginal Road between Alges and Cascais in Portugal. The aim of this study was to produce a philosophy for a strategy to select the best safety measures out of several which had already been proposed. The general point of departure in this philosophy is the relation between the function of a road-connection, its layout, and the resulting behaviour of road users. It appears that the blocks with a length of 8 km have 80% of the registered accidents on the "Marginal". The uneven distribution of accidents cannot be explained by differences in traffic volume. The functional inhomogeneity of the road layout is considered to be one of the main causes of accidents on the "Marginal". On the one hand, the lack of safety cannot be related either to road user bad behaviour or to bad vehicle or road maintenance. On the other hand, it is supposed that some safety improvements in these fields can be achieved. The construction of a new motorway from Lisbon to Estoril is an important condition for the recommendations. For the selection of, for instance, the appropriate measures more information is needed on: (1) the environmental planning of the area around the "Marginal"; and (2) the environment where junctions and bends have to be improved due to the high demands of the traffic flow function.
Abstract