Barrier-Free Ring Structures and Pedestrian Overlaps in Signalized Intersection Control

Abstract

Compared with the ring-barrier framework used for ring structures (or phasing plans) in signalized control of intersections in the United States, the Dutch framework has no explicit barriers, but only a requirement to respect pairwise conflicts. This paper describes how ring structures can be modeled with pairwise conflicts as a starting point. Modeling techniques were extended to account for offset constraints such as leading pedestrian intervals in which the start or end of one traffic movement was constrained by the start or end of another one that was otherwise compatible. One practical drawback of the more flexible Dutch framework is that it permits so many more possible ring structures that it can be prohibitive to evaluate them all manually. Therefore, this paper describes VRIGEN, an automated method that overcomes this drawback by identifying and evaluating all possible ring structures. Finally, this paper presents several examples in which barrier-free ring designs allow signals to cycle more quickly and efficiently, with improvements in safety and delay for pedestrians and bicyclists. Most of these examples feature pedestrian phases that are allowed to overlap while their parent vehicular phases are not.