Extensions of theoretical capacity models to account for special conditions

The computational procedures used to analyze two-way stop-controlled inters ections were extended in the National Cooperative Highway Research Project 3-46 to account for a number of effects commonly observed at actual unsigna lized intersections. This paper presents theoretical extensions that can ac count for commonly observed phenomena, such as two-stage gap acceptance whe n 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 s hared left-turn and through lanes. The individual effects are then combined into an analytical framework suitable for inclusion in the Unsignalized In tersections procedures of the 1997 "Highway Capacity Manual". (C) 1999 Else vier Science Ltd. All rights reserved.