Abstract
The basic model of traffic operations at signalized intersections is based on the assumption that when a signal changes to green, the flow across the stop line increases rapidly to saturation flow rate, which remains constant until either the queue is exhausted or the green period ends. In recent years, this assumption has been challenged by some field observations in Taiwan and U.S.A. These observations showed marginal increase in queue discharge rate along the queued vehicles’ position. This paper investigates queue discharge behavior at signalized intersections based on video data collected from one of the busiest at-grade intersections. The methods proposed in the HCM (2000) and Australian Road Research Report 123 to estimate saturation flow rates were assessed against field observations. The results from field observations were similar to those observed in Taiwan and U.S.A., whereas the micro-simulation results went against some common perceptions that believed micro-simulation under represents queue discharge rate.
