Introducing the concept of alternative intersections with three-phase traffic signals

Abstract

At intersections where traffic demand is above capacity, reducing the number of signal phases may help operational performance. Alternative intersections may help achieve the reduction; however, retrofits to alternatives with two-phase signals may be impactful and unpopular. Our study evaluates five alternative signalized intersections with three critical phases, namely partial median U-turn intersection (MUT), partial continuous-flow intersection (CFI), a combination of MUT and CFI (MUT/CFI combo), reverse reduced conflict intersection (reverse RCI), and thru-cut. Three-phase designs may provide better capacity than conventional intersections with fewer impacts than two-phase intersections and, therefore, may be more palatable to stakeholders. A wide range of simulation scenarios were tested to evaluate the performance of the intersections using VISSIM and the Surrogate Safety Assessment Model. Based on the results, all three-phase designs outperformed the conventional design in terms of traffic operation. The partial CFI and MUT/CFI combo yielded the fewest conflicts among the designs evaluated.