Extensions of theoretical capacity models to account for special effects of two-stage gap acceptance; flared minor-street approach; upstream signals; pedestrian crossings; and delay to major-street through vehicles.

The computational procedures used to analyse two-way stop-controlled intersections were extended in the National Co-operative Highway Research Project 3-46 to account for a number of effects commonly observed at actual unsignalised intersections. A summary of theoretical extensions that can account for commonly observed phenomena, such as two-stage gap acceptance when median storage is available; right-turn "sneakers" at flared minor-street approaches; non-random arrivals caused by upstream signals; impedance due to pedestrian crossings; and delay to major-street through vehicles using shared left-turn and through lanes is summarised. The individual effects are then combined into an analytical framework suitable for inclusion in the unsignalised Intersections procedures in the 1997 Highway Capacity Manual. (A)