An Improved Method for Estimating Sign-Controlled Intersection Capacity

This paper discusses the gap acceptance parameters recommended by the Austroads Road Design and Traffic Management Guides and the US Highway Capacity Manual, and describes a new method developed for the SIDRA INTERSECTION software for determining the critical gap and follow-up headway parameters for two-way stop and give-way sign controlled intersections as a function of intersection geometry, control and flow conditions. The method allows for the relationship between driver gap acceptance parameters and intersection geometry (number of lanes on the major road, one-way major road, T-intersection), minor road grade, reduced gap acceptance parameters for two stages of a staged crossing movement, special consideration of U-turn movements, differences in driver gap acceptance behaviour between give-way and stop sign control, decreases in critical gap and follow-up headway values with increased opposing flow rate, and the effect of movement classes (light vehicles, heavy vehicles, buses, bicycles, and so on). An example is given to demonstrate significant differences that may occur in gap acceptance parameters and the corresponding capacity and performance results under different geometry and control scenarios.