Abstract
The positive effects of active mobility on mental and physical health as well as on air quality are widely acknowledged. Increasing the share of active travel is therefore an aim in many countries. Providing bicycle-safe infrastructure is one way to promote cycling. Roundabouts are a common traffic infrastructure and are supposed to facilitate safe and smooth traffic flow. However, data on road traffic accidents indicate an over-proportional involvement of cyclists in accidents at roundabouts. In the present study, the influence of roundabout geometry and traffic flow on bicycle accident occurrence was investigated using a logistic regression approach on twelve parameters of N = 294 mostly small- and mini-sized single-lane roundabouts in the Canton of Berne, Switzerland. Average weekday motorized traffic was identified as a major factor in explaining bicycle accident occurrence at roundabouts. Further, the radius of the central island, the location of the roundabout (in town vs. out of town) and the number of legs were significantly related to bicycle accident occurrence. While these results are in general agreement with findings from similar studies, the findings regarding the central island’s radius and the number of legs underpin the need for roundabout type-specific studies: Some parameters may not prove relevant in intermediate- to large-sized roundabouts, but become critical in small or mini roundabouts, which are common in Switzerland and numerous in the present sample.
Highlights
In Switzerland, the construction of roundabouts, in addition to, or to replace regular intersections, started in the 1980s [1]
By contrast, inscribed circle radius (ICR), circulatory roadway width (WIDTH), minimum sector angle, maximum eccentricity of the legs’ axes (MAX_ECC), presence of pedestrian crossings (ZEBRA) or bicycle lanes (BIKE) on the legs, view across the central island (VIEW) and motorized traffic load distribution (LOAD) are not significantly associated with bicycle accident occurrence
This paper details results from a logistic regression analysis of roundabout design and bicycle accident occurrence on a sample of N = 294 single-lane roundabouts in Switzerland
Summary
In Switzerland, the construction of roundabouts, in addition to, or to replace regular intersections, started in the 1980s [1]. While considerable attention has been given to the formulation of safety guidelines for roundabout design [1,5,10,11] and management [12,13], as well as analysis of bicycle accident occurrence at roundabouts [8,9,11], extensive structural analyses of operating facilities with respect to the identified risks for cyclists are still missing for Switzerland c.f. [1,8,13]: Early on, the influence of a large number of geometric properties on general roundabout safety was studied on a relatively small sample of roundabouts in Switzerland (N = 32) [1].
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