Similarities and dissimilarities of road accident patterns for chosen types of urban intersections.

In this work a safety research has been undertaken to determine road accident patterns that are typical to accident place. Accident features subjected to investigation were accident type and drivers' behaviour. As features that characterise accident place the following features have been chosen: unsignalised ordinary and channelled intersection and combinations of vehicle relations at these intersections that generate road accidents. Accidents with pedestrians have been excluded from the analysis. Accident patterns identified for the two types of intersections allow coming to some conclusions. The arrangement of accident types according to their frequencies is the same for both ordinary and channelled intersections. The same arrangement can be noticed for these types of intersections in the context of dominant combinations of vehicle relations, i.e. S-S and L-S. The arrangement of drivers' behaviour according to their frequency of occurrence in road accidents is the same for both ordinary and channelled intersections. There are however differences in such arrangement when the combinations of relations of vehicles involving in accidents are considered. In the case of the L-S combination disobeying priority is, in principle, the only cause of accidents at channelled intersections. The geometrical solution of unsignalised intersection with channelled traffic changes accident patterns for the S-S combination of vehicle relations. In this case rear-end collisions occur two times more rarely than side collisions, whereas at ordinary intersections these accident types occur equally often. For channelled intersections the number of accidents with the R-S combination of vehicle relations is much smaller than for ordinary intersections. The most frequent, in relation to accident numbers, S-S combination of vehicle relations is characterised by drivers' behaviour pattern that depends on the type of intersection. At channelled intersections disobeying priority results in accidents two times often than mismatching speed and distance to a traffic situation, whereas at ordinary intersections these causes occur equally often. (A) For the covering abstract of the conference see ITRD no 207828. The reprints are also available at the web - http://www.vti.se/pdf/reports/K18APart1.pdf; http://www.vti.se/pdf/reports/K18APart2.pdf and http://www.vti.se/pdf/reports/K18APart3.pdf.