Design and analysis of roundabouts

The authors note that Victorian roundabouts have been operating under a priority rule for many years, that is entering drivers give way to circulating drivers. This paper demonstrates that for Australian roundabouts (or at least Victorian roundabouts) capacity can be suitably estimated using a gap acceptance theory; they need not be large to achieve high capacities; they generally have operating characteristics superior to conventional alternatives; and their geometry should be devised to assist the driver performing the gap acceptance task. The paper contains suggestions relating to layout, and line marking and details the capacity analysis of two roundabout designs which are superior to signalised intersection alternatives.