Intersection lay-out, priority rules and traffic safety.

This paper reports on the accident research carried out as part of a large project on priority rules at unsignalized intersections, started in 1983 at the SWOV Institute for Road Safety Research at Leidschendam in the Netherlands. An inventory was made of a large number of intersections, for which layout features, accident data, and traffic volumes were recorded. Detailed traffic counts were made at a subset of these intersections. The paper discusses the preparations for this activity, its analysis, and its results. It was found that intersections in built-up areas cannot be classified into groups on the basis of layout characteristics or traffic volumes; the accidents occurring there involved a wide variety of vehicle types and manoeuvres. Nevertheless, some characteristic patterns were found in the distributions of accident types for T-junctions and crossroads, with and without a priority rule. Some of the hypotheses extracted from the interpretations of the accidents may be checked or investigated further in other parts of the project. Not only is further research needed, but also the data already collected during the project provide many opportunities for new analyses.