Operational Analysis and Signal Design for Asymmetric Two-Leg Continuous-Flow Intersection

Abstract

Despite the increasing implementation of the continuous-flow intersection (CFI) in practice, the development of reliable guidelines for its operational analysis and signal design remains in its infancy, especially for the popular two-leg asymmetric CFI design, because of the relatively low cost and desirable efficiency. For best use of the capacity of such a CFI design, a signal optimization model is presented; it can serve as an effective tool for engineers to design the cycle length, phase duration and sequences, and offsets for both its primary and subintersections. By accounting for the commonly encountered constraints of short bay length for turning movements and the interrelations between critical flow movements, the proposed model can prevent queue spillover on left-turn bays and offers concurrent progression for both the through and left-turn flows. To ensure the applicability and effectiveness of the proposed model, this study further uses the data from a proposed asymmetric CFI in Maryland for performance evaluation. The results of extensive simulation with field data confirm that the proposed signal optimization with its capability to account for all physical constraints and flow conflicts can indeed perform as expected; that is, it offers concurrent progression to both through and left-turning flows and prevents any queue from spilling over its designated bay.