This paper discusses the gap acceptance methods of evaluating the capacity of unsignalised intersections, including roundabouts, which are described in the Australian State Road Authorities' two intersection design guides. It compares these methods with those in the 1985 Highway Capacity Manual; most of the mathematical techniques used have been based on Tanner's results. It assesses some recent Australian researches on traffic on unsignalised intersections, which cover the following aspects: (1) gap acceptance parameters and the distribution of accepted and rejected gaps; (2) absorption capacity for two levels of priority; (3) absorption capacity for three levels of priority; (4) average values for the delay before a vehicle can cross an intersection; (5) crossing with shared priority. Finally, there is a discussion of possible future Australian research on unsignalised intersections; more work is needed on gap acceptance parameters and on flow and headway distributions along road links, under Australian road traffic conditions.
Abstract