Analysis of Saturation Flow at Signalized Intersections

The accuracy of saturation flow values is of prime importance when determining the capacity of signalized intersections. The objective of this study was to collect a large sample of field measurements so that reliable saturation flow values could be obtained and the factors affecting saturation flow could be identified. The results identified several factors which had significant influence on saturation flow. A formula was recommended for use in estimating an appropriate saturation flow value for a specific lane on an approach to an intersection. Adjustment factors were applied to a "base'' saturation flow value. Adjustments were developed for the following factors; location in city, city population, vehicle type and turning maneuver, gradient, width of lane, turning radius (jar right-turning vehicles), pedestrian activity, type of lane, speed limit, and light condition.