Roundabouts : some remarks on the safety and capacity of roundabouts and roundabout priority systems. Contribution to discussions, in CEMT/CCRS and CSR meetings on 9 - 11 September 1986.

This report considers what contribution roundabouts and roundabout priority systems can make to the safety and capacity of intersections. Conclusions drawn are: (1) the use of roundabouts merits greater consideration, both as an alternative to traffic lights at busy intersections and as a means of reducing speed at quieter junctions. Careful consideration should be given to the use of roundabouts on roads carrying fast traffic outside built-up areas. (2) the capacity range of roundabouts is very large, up to some 4000 vehicles an hour provided traffic on the roundabout has priority. (3) the priority system for roundabouts should be standardized, not only nationally but also internationally. The system where traffic on the roundabout has priority would seem to be the best choice at the moment. Roundabouts should be designed with this in mind, eg with radial approaches and a suitable radius of curvature. (4) research should be carried out into the desirability of roundabouts in situations with a lot of slow traffic and the position of slow vehicles on roundabouts; in built-up areas there would seem to be some advantage at the moment in having cycles and mopeds use the roundabout. There is no indication that roundabouts are less safe for slow vehicles than are other types of intersection.