Traffic Signal Phase Truncation in Event of Traffic Flow Restriction

Abstract

This paper proposes an improvement to traffic signal controller logic. The concept consists of truncating a phase on which there is demand but with zero or minimal flow owing to a restriction of traffic. Flow restrictions occur for a variety of reasons including queue spillback, stalled vehicles, and railroad blockages. The logic presented in this paper recognizes such a flow restriction and, consequently, terminates the phase in favor of a conflicting call for service. The theory of the concept is addressed, and methods of implementation are explored. Although this research focuses on phase truncation, terminating a phase may not always be the most strategic decision; other priorities can override tactical detection of minimal flow. Therefore, this research considers the feasibility and potential benefit of including phase truncation logic as one component of a more intelligent and strategic controller algorithm. A limited experimental analysis was conducted to qualify the benefit of the phase truncation concept. This analysis was conducted with VISSIM simulation software in conjunction with a hardware-in-the-loop configuration. On the basis of the results of this analysis, which was limited in scope, it was concluded that the phase truncation concept could result in reduced vehicle delay under at least one traffic scenario.