This paper presents a simple whole-junction model, which incorporates a relation between speed and accident risk that has recently been established for urban road links. The proposed model offers a unified explanation of several features of priority junctions, that were previously described by various empirical relations. Such relations are explained, in terms of speed changes on the major road. A speed-dependent mathematical model is formulated. Predictions are made from the model for: (1) isolated junctions; (2) a series of junctions along a route; and (3) a staggered crossroads. The following testable hypotheses can be derived: (1) accidents vary as the square of traffic speeds; (2) accident rates per vehicle (2) accident rates per vehicle on major or minor roads are constant at low flows; (3) accident totals along the road are relatively independent of the number of junctions, if the junctions are not close enough to interact; (4) replacing crossroads by T-junctions has rather a small effect; and (5) staggered crossroads reduce accidents substantially, even at higher flows. The simple model seems to be reasonably general.
Samenvatting