Priority System for Multimodal Traffic Signal Control

There are many users of signalized traffic intersections including passenger vehicles, commercial vehicles/trucks, pedestrians, bicycles, transit buses, light rail vehicles, snowplows, and emergency vehicles such as fire trucks and ambulances. North American approaches to traffic signal control are centered on general vehicles with either accommodations for other modes or exceptions for special considerations such as emergency vehicles. This paper presents a unified decision framework for multi-modal traffic signal control that simultaneously considers the needs of different modal users based on wireless communications, as well as traditional detection methods. This framework is based on a mathematical optimization model where each modal traveler can request service using priority requests. The mathematical programming framework allows multiple priority requests to be considered simultaneously based on a hierarchical control policy. In addition to modal users, system-operating principles such as coordination are included as priority requests within the decision framework. The system has been developed and tested using both microscopic traffic simulation and in a live network of six intersections in Anthem, Arizona using emerging technology developments in Connected Vehicle systems. The responsible operating agency must establish a policy for each equipped section of traffic signals that determines the relative importance of different modes of travel. For example, one section might be selected to be pedestrian and transit friendly and another section might be selected to be truck friendly. This priority policy would impact how the signal timing is adapted to accommodate the multiple active requests for priority. This paper explores the ability of the section priority policy within the unified priority control decision framework for multi-modal travelers to provide improved quality of service for each mode within the structure of the priority policy.