On-line decisions about permitted/protected left-hand turns in distributed traffic signal control

Abstract

A long-term project was started some time ago, using a distributed and knowledge-based methodology for realtime, traffic-adaptive control for streets and highway ramps. In this paper, it is argued that the traffic scenarios fully determine whether a protected or a permitted left-hand turn is needed. A flexible and inexpensive on-line decision methodology is described, concerning the phasing regime at an intersection. Simulation experiments have shown that this integrated Intersection Analyzer, coupled with a signaling (phasing and timing) system, performs better than the empirical “50,000 rule” described by McShane and Roess (Traffic Engineering, Prentice Hall, Englewood Cliffs, NJ, 1990) in all configurations and traffic densities. While some of the expert systems described in the literature may approximate the quality of the new system in some instances, they lack the flexibility and generality of the approach described in this paper.