Coordinated Optimization Model for Signal Timings of Full Continuous Flow Intersections

Abstract

The continuous flow intersection (CFI) was invented by Francisco Mier to improve traffic operation in intersections that suffer from traffic problems caused by high numbers of left-turn movements. Although the CFI has been developed for 25 years and some built CFIs have achieved good results, it lacks a general model of signal timings and offsets. This paper (a) describes the main relationships needed to develop a CFI model; (b) builds a detailed model for optimization of phase sequence scheme, length of cycle, phase durations, and offsets between successive signals; and (c) compares the computing results of minimum cycle, capacity, and average delay of CFIs with those of conventional intersections. The results show that CFI has a clear advantage and a wide range of application. In the proposed model and algorithm, the location of the subintersection as a design parameter need not be input, but it is affected by offset and queue length. The solving process and algorithms of all critical features, such as average delay, are provided. The simplified solving process makes this model easy to apply; the computation is not onerous and can be made with the help of a simple procedure running on a personal computer.