Abstract
This paper demonstrates that for Australian roundabouts (a) their capacity can be suitably estimated using a gap-acceptance theory, (b) they need to be larged to achieve high capacities, and generally have operating characteristics superior to conventional alternatives, and (c) their geometry should be devised to assist the driver performing the gap-acceptance task. Suggestion relating to lay-out, line marking and details of capacity analysis of two roundabout designs are appended.