Accident prediction models for roundabouts.

The management of speed is considered an important safety issue at roundabouts. The approach speed and negotiating speed through roundabouts depends on both the geometric design of the roundabout and sight distance. In New Zealand and in the Australian States the design standards (based on Austroads) recommend long approach sight distance and provision of relatively high design speeds. This is in contrast to European roundabouts where visibility is normally restricted and the geometric design encourages slow approach and negotiation speeds. The earlier flow-only models (models with only flow predictor variables) have been extended to include non-flow variables, such as sight distance, intersection layout and observed speed variables. Models have been produced for the major motor-vehicles only, pedestrian versus motor-vehicles and cyclists versus motor-vehicle accident types.Flow-only models have also been produced for roundabouts on roads with high speed limits. The models have then been used to assess whether a move towards the European design philosophy, of lower speed and reduced sight distance, may lead to lower accident rates for all modes, particularly in areas that have high concentrations of pedestrians and cyclists. (a) For the covering entry of this conference, please see ITRD abstract no. 0612AR242E.