Archived project

Roundabout Crash Prediction Models

Goal: Development of SPFs/CPMs for roundabouts including cyclists

Date: 1 January 2007 - 1 January 2009

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Project log

Shane Turner
added a research item
The management of speed is considered an important safety issue at roundabouts. The approach speed and negotiating speed through roundabouts depends on the geometric design of the roundabout and sight distance. In New Zealand and in Australia, the design standards recommend long approach sight distances 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. This work, undertaken in 2006, extends previous research by the authors developing crash prediction models at roundabouts to include 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 crash types. Flow-only models have also been produced for roundabouts on roads with high speed limits. The models produced indicate that roundabouts with lower speeds (observed and speed limit), fewer approach lanes and reduced visibility have lower crash rates.
Shane Turner
added 3 research items
Roundabout design in New Zealand generally follows the Austroad guideline for intersection design (Austroads, 2005), which recommends long approach sight distances and provision of relatively high design speeds. This is in contrast to European based design philosophy where visibility is normally restricted and the geometric design encourages slow approach and negotiation speeds. This paper reports on the results of a study that used crash prediction models to investigate how the characteristics of roundabouts influences safety at 104 roundabouts in three centres. Using a dataset that contains pedestrian, cyclist and motor vehicle flows, approach and circulating speeds and sight distances an analysis was carried out for a number of crash types and new crash relationships established. It will be shown that safety benefits can be achieved by a more European based design philosophy.
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 'flow-only' models developed in Turner (2000) have been extended to include 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, is likely to produce lower accident rates for all modes, particularly in areas that have high concentrations of pedestrians and cyclists.
Shane Turner
added a project goal
Development of SPFs/CPMs for roundabouts including cyclists