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.

Adaptive Walk Intervals

“…Those safety requirements, laid out in the Manual on Uniform Traffic Control Devices (1), as well as the Traffic Signal Timing Manual (2), consist mainly of a policy minimum length for the walk interval (W o )-7 s is recommended for W o although 4 s may be used in exceptional cases-and sufficient pedestrian clearance time, the crossing length divided by a low-percentile pedestrian speed, usually taken to be 3.5 ft/s. Recent research on reducing pedestrian delay includes attention given to two-stage pedestrian crossings (3,4), longer permissive intervals for actuated pedestrian phases (5), overlaps involving leading pedestrian intervals that can reduce cycle length requirements (6), and exploring the use of fully actuated versus coordinated control at different levels of vehicular and pedestrian demand (7). Because pedestrians tend to arrive without a coordinated pattern (except at multistage crossings), reducing pedestrian delay is mainly a matter of shortening the signal cycle or lengthening the walk interval, or both (8).…”

“…Recent research on reducing pedestrian delay includes attention given to two-stage pedestrian crossings (3,4), longer permissive intervals for actuated pedestrian phases (5), overlaps involving leading pedestrian intervals that can reduce cycle length requirements (6), and exploring the use of fully actuated versus coordinated control at different levels of vehicular and pedestrian demand (7). Because pedestrians tend to arrive without a coordinated pattern (except at multistage crossings), reducing pedestrian delay is mainly a matter of shortening the signal cycle or lengthening the walk interval, or both (8).…”

Overview and Modeling Capabilities of an Event-Based Signal Controller

“…While the RBC serves as a valuable simplification for typical intersection layouts, it can also be constraining when a movement on one side of a barrier conflicts with some, but not all, of the movements on the other side, creating unnecessary delay to those movements. Evaluations found the use of pedestrian overlaps can significantly reduce pedestrian delays compared to basic traditional signal control [23]. This limitation cannot be addressed within the fundamental structure of RBC unless introducing additional phases and overlap phasing [24].…”

Prioritizing Cyclists at Signalized Intersections Using Observations from Connected Autonomous Vehicles

“…VA control uses information about the current traffic state to control the use of conflict areas, that is, the areas where two conflicting movements meet. The order in which opposing directions receive green is based on a fixed control structure, with stages of nonconflicting movements constructed with the aid of pairwise conflicts ( 5 ). The order of the phases is red–green–yellow, and yellow time is based on the speed of the traffic and the distance within which traffic can choose whether to proceed or stop, the so-called dilemma zone.…”