Self-Organizing Control Logic for Oversaturated Arterials

Abstract

Decentralized, actuated traffic signal control has many advantages, but it lacks mechanisms for coordinating with other signals along an arterial. When an intersection along an arterial is near or at oversaturation, coordination can play an important role in preserving and utilizing capacity by preventing spillback and starvation. Rules that can be added to a base of decentralized, clock-free actuated control are proposed for managing queues during periods of oversaturation. These rules are part of a larger framework for developing logic that will make arterial traffic signals self-organizing rather than organized around a common signal cycle. Features of the proposed logic include green truncation in case of intersection spillback, early green and double realization for left-turn phases prone to pocket spillback resulting from a limited turn-bay length, and dynamic coordination for groups of signals spaced too close together to hold a normal cycle's queue. With dynamic coordination, green waves are scheduled for each cycle following the critical intersection's critical arterial through phase, with noncritical intersections adjusting offsets based on queue counts and a logic. The proposed dynamic coordination logic allows temporary spillback at upstream intersections to prevent starvation at the critical intersection and temporary starvation at downstream intersections to prevent spillback at the critical intersection. Simulation tests using a benchmark network showed 45% less delay than standard coordinated control and 4% less than an optimizing control method designed for oversaturated arterials. Simulation tests on two realistic networks also showed delay reductions of 8% and 35% compared with coordinated control.