Authors: Xianfeng Yang, Yao Cheng and Gang-Len Chang
Journal: Journal of the Transportation Research Board (TRR),2015
Unconventional Design: Asymmetric Two-leg CFI
Purpose: Developed a signal optimization model for asymmetric Two-leg CFI by concurrently optimizing both the phase sequence and offsets.
Despite the increasing implementation of Continuous Flow Intersection (CFI) in practice, the development of reliable guidelines for its operational analysis and signal design remains at the infancy stage, especially for the popular two-leg asymmetric CFI design due to its relative low cost and desirable efficiency. To best utilize the capacity of such a CFI design, this paper presents a signal optimization model that can serve as an effective tool for engineers to design the cycle length, phase duration and sequences, and offsets for both its primary and sub intersections. 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 the queue spillover on left turn bays, and offer concurrent progression for both the through and left-turn flows. To ensure the applicability and effectiveness of the proposed model, this study has further used 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, offering concurrent progression to both through and left-turning flows and preventing any queue from spilling over its designated bay.