Vulnerable road user safety at roundabouts: empirical results

Abstract

This paper presents the results of recent research on safety for different types of road users at roundabouts. In general, roundabouts are believed to be safe and smooth intersection types. The conversion of an intersection into a roundabout has been proven to reduce the number of crashes with injuries or fatalities. Nevertheless, some doubts persist about the safety effects for vulnerable road users, in particular for bicyclists. Regression models were developed in order to explain variations in crash counts among roundabouts. Data on injuries, traffic volumes and roundabout geometry were collected. The results show that the variation in accident counts is relatively small and mainly driven by the traffic exposure. Confirmation was found for the existence of a “safety in numbers”-effect for bicyclists, moped riders and – more uncertain – for pedestrians at roundabouts. Vulnerable road users (moped riders, motorcyclists, bicyclists and pedestrians) are more often involved in injury crashes at roundabouts then could be expected based on their presence in traffic. Moped riders and motorcyclists are overrepresented in single-vehicle crashes whereas moped riders and bicyclists are overrepresented in multiple-vehicle crashes. A before-and-after study of injury accidents with bicyclists on 90 roundabouts in Flanders-Belgium was carried out. The study design accounted for effects of general safety trends and regression-tothe-mean. Conversions of intersections into roundabouts turned out to have caused a significant increase of 27% in the number of injury accidents with bicyclists on or nearby the roundabouts. The increase was even higher for accidents involving fatal or serious injuries (41-46%). Roundabouts with cycle lanes close to the roadway appeared to perform significantly worse compared to other design types. Also roundabouts that were replacing signal-controlled intersections had a worse evolution compared to roundabouts on other types of intersections.