Effect of Upstream Signal on Nonpriority Movement Capacity and Delay

Abstract

A methodology is described for estimating the capacity of and the delay to nonpriority movements at a two-way stop-controlled (TWSC) intersection in the presence of an upstream signalized intersection. The methodology is centered around the capacity of and the delay to the major-street left-turn movement; however, it is also directly applicable to the minor-street right-turn movement. With some adjustment, the methodology can also be applied to minor-street left and through movements. The findings indicate that upstream signals have a significant effect on the capacity and delay of nonpriority movements at TWSC intersections. Specifically, the traffic platoons formed by the signals tend to increase capacity and decrease delay. The magnitude of the effect of the upstream signal is dependent on the amount of platoon dispersion that takes place as the platoon travels down the street. Several factors affect the rate of platoon dispersion, including travel distance, level of driveway activity, and the arterial cross section. A rationale is presented for inclusion of a minimum, nonzero capacity for nonpriority movements. This minimum capacity approximately accounts for behavior of drivers confronted with lengthy delays and in the presence of platooned traffic flows. The minimum capacity value providing the best fit to the simulation data was 165 vehicles per hour.