Turboroundabouts Multicriterion Assessment of Intersection Capacity, Safety, and Emissions

A turboroundabout is a variation of the conventional multilane roundabout in which spiral road markings and raised lane dividers force drivers to follow a specific path according to their intended destination. This geometry eliminates weaving and cut-in conflicts by guiding drivers continuously from entry to exit. Turboroundabouts were conceived with the main aim of improving safety, but their practical benefits are relatively unknown. Likewise, the few existing studies on turboroundabouts do not allow definitive conclusions to be drawn about the delay and emissions performance characteristics of turboroundabouts; further research is needed. This research focused on the use of appropriate modeling methodologies to understand the effects of turboroundabouts on capacity, safety, and emissions in comparison with the effects of conventional single-lane and double-lane roundabouts. The results indicate that turboroundabouts have capacity levels comparable to those of two-lane roundabouts but are less robust concerning the directional split of the entry traffic; turboroundabouts lead to fewer traffic conflicts, but the traffic conflicts that do occur are more severe. The results also show that the implementation of turboroundabouts provides no advantages for emissions when the main concerns are carbon dioxide and oxides of nitrogen.