Study of Safety in Roundabouts in Dual Carriageways
By Dan Kashinsky & Dr. Doron Balasha
The Research was financed by The Research Fund on Insurance Matters Affiliated with the Israel Insurance Association (RA)
Abstract
A traffic circle (roundabout, rotary) is a particular kind of traffic arrangement for single-level intersections, differing from regular intersections in its geometry and in its action.
In Israel, as elsewhere in the world, the roundabout-type traffic arrangement is playing an increasing role as the preferred intersection arrangement in certain conditions, and as one that has proved itself in reducing the number of accidents where it is installed.
After proving itself to be effective, planners began, mainly abroad, to implement it at intersections with larger and larger volumes of traffic, leading to the creation of double-lane and even multi-lane roundabouts, both in the approach to the roundabout and in the width of the carriageway encircling it.
However, unlike the single-lane roundabout, where the driver's behavior is dictated in an unambiguous manner, both in the approach to the roundabout and in it, with the multi-lane roundabout the driver follows one of a number of traffic lanes and, other than the road markings, his route, both approaching and on the roundabout, is left to his decision and to his best judgment and driving skill.
Additionally, the dimensions of the roundabout have grown considerably, both in the approach roads and the roundabout itself, resulting in longer pedestrian crossings and more complex cyclist integration, and leading to a higher accident rate at these roundabouts by comparison with those with a single lane.
The question is, therefore, whether or not the safety target is being achieved in full, and if so, to what extent and why this is the case in certain types of roundabout. This is the subject under examination in this paper.
Existing knowledge in leading countries around the world in the field of traffic research on the subject was studied through a comprehensive review of the literature in Israel and around the world, in order to learn the outcome of research studies, existing planning guidelines, and the engineering means for reducing accidents on roundabouts on multi-lane roads.
The situation in Israel was then examined in depth, in two ways:
One, an analysis of the characteristics of accidents taking place on roundabouts chosen for the purpose of the study of multi-lane roads, and classification of the results by the existing types of roundabout.
Two, examination of road-user behavior at these intersections through observations and recording the incidents occurring there. These, too, were classified by characteristics and cross-referenced with the findings regarding accidents.
Finally, recommendations were formulated with regard to adapting the engineering means in order to reduce the scope and severity of accidents at roundabouts on multi-lane roads.
