Determination of Capacity at All-Way Stop-Controlled Intersections

Abstract

A new theoretical approach for the determination of capacity at all-way stop-controlled (AWSC) intersections is presented. This approach is based on the addition-conflict-flow method developed from graph theory. The new approach takes all the traffic streams into account, in contrast to existing procedures, which handle only the approaches. It allows a systematic and realistic analysis of the traffic process at AWSC intersections. The new approach can deal with most common lane configurations in the real world. A simple and more practical procedure is recommended. In practice, this simplified procedure can be used for single-lane approaches as well as approaches with separate left-turn traffic lanes. This procedure is verified and calibrated with measured data. For the calculation of capacity at AWSC intersections, general parameters, which are found by calibration, are proposed. The new procedure produces results more precise than the existing ones compared with the measured data. As a result, the maximum total capacities of AWSC intersections with single-lane approaches are found to be between 1,500 and 1,900 passenger cars per hour. The total maximum capacities of AWSC intersections with single-lane approaches and separate left-turn lanes are between 1,800 and 1,950 passenger cars per hour. Furthermore, the procedure shows that additional (left-turn) lanes significantly affect capacity increases only for asymmetric street-flow splits. The present procedure can easily be extended to AWSC intersections with multilane approaches.