Roundabouts are a popular choice for intersection control around New Zealand, particularly for replacing priority controlled intersections where traffic volumes are high and safety has deteriorated. However, safety problems can occur at poorly designed roundabouts, particularly where speed is not managed well and where cycle volumes are high.
Despite their generally good record, safety deficient roundabout designs have received considerable attention from safety auditors over the last 10 or so years. This culminated in the publication of the guide The ins and outs of roundabouts. This guide lists problems encountered in 50 safety audit reports. The guide lists visibility and geometric design features, particularly inadequate deflection and marking, as problem areas. The guide states that ‘the safe and efficient movement of traffic relies on good unobstructed lines of sight’. The provision of good visibility at roundabouts follows the guidance in the Austroads Guide to traffic engineering practice part 6: roundabouts. This practice, which occurs in New Zealand and Australia, differs to practice in other parts of the world, particularly Europe, where visibility is often restricted to reduce speeds and improve safety. This discrepancy was a major motivator for this research project.