Operational Effects of Continuous Flow Intersection Geometrics

The continuous flow intersection (CFI), also known as a displaced left-turn (DLT) intersection, increases capacity and reduces delays by eliminating the left-turn traffic signal phase. The geometric layout of the intersection is changed so that left turns cross opposing traffic lanes at a location upstream of the main intersection. Although the installation of CFIs has become more prevalent in the United States, insights into the geometrics of CFIs gained through their application have not yet been dispersed to industry or academia. This paper considers the impacts that geometric design has on the operations of CFIs. The paper presents a deterministic model that considers the effects of the DLT length and other CFI geometrics on traffic operations. Although academic in nature, this model evolved through practical application. The model takes functional and operational insights gained through the analysis, design, and observation of multiple operational CFIs in Utah and articulates them in mathematical terms. The quantitative relationships presented provide transportation professionals and officials more accurate and precise guidance to facilitate better decisions in considering, evaluating, and designing a CFI.