Report 285 Cyclists at roundabouts - the effects of 'Continental' design on predicted safety and capacity

Publication Year

1997

Document Status

Current

Abstract

The purpose of this report is to investigate schemes providing for the safe and convenient movement of cyclists at roundabouts. Roundabouts are becoming increasingly common in Continental Europe. The design of roundabouts in countries where cycling is more prevalent is considered to be more 'cycle friendly'. In particular, the geometry tends to be much 'tighter'. The capacity of this type of roundabout is less than that of an equivalent-size UK design roundabout, but still adequate for peak vehicle inflows of up to 2,500 per hour. This report describes a study which uses the TRL traffic model ARCADY/3 (Assessment of Roundabout Capacity and Delay/Version 3) to assess the potential effects on capacity and accidents of modifying a variety of existing roundabouts to a 'Continental' design. The key features of this Continental design are: arms that are radial, instead of tangential, to the roundabout centre. single lane entry and exists (widths 4-5m) minimal flare on entry. an inner circle (central island) of 15-25m diameter. an external (inscribed circle) diameter of 25-35m. a circulatory carriageway of 5-7m. cycles continue to mix with other traffic and normal priorities are retained.

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