Previous research has suggested that existing signal analysis software and guidelines are deficient in their analysis of closely-spaced, or paired, intersections. In particular, the phenomenon of downstream queues interfering with upstream movement discharge has not been incorporated. This paper presents a methodology, which specifically takes into account the effects of blocking, for determining the capacities of movements at simple paired intersections. The underlying assumption of the model is that discharge of a movement at an upstream intersection will continue at saturation flow rate until a downstream queue extends back to the upstream intersection. This assumption leads to a simple graphical technique for determining movement capacities based on parameters easily measured in the field or estimated using elementary formulae. Many features of paired intersections, such as multiple upstream movements and multiple upstream and downstream green periods, can be analysed using the model. Some results of a comparison of the model estimates with output from a microscopic simulation program are presented. The model is also applied to a staggered T-intersection in Sydney, Australia. (A)
Samenvatting