Evaluation of Triangabout as Alternative for Intersection with Nonthrough Arterial Movement

Abstract

At the majority of signalized intersections along an arterial, the mainline movement passes straight through the intersection. At four-leg intersections where the major arterial movement is not a through movement (i.e., an L-shaped corridor vertex), the intersection can sometimes experience more congestion than adjacent intersections along the corridor because the two minor approaches, which are adjacent conflicting movements, must be served in a split-phase fashion. A new, unconventional intersection design, referred to as a “triangabout,” is proposed to improve mobility and enhance safety for such intersections. The two approaches that are the mainline arterial form two legs of a triangle and a new diagonal section of roadway connecting those two legs is the hypotenuse. Flow within the triangabout is one-way counterclockwise, similar to a roundabout. The three intersections at the vertices of the triangle are signalized to provide a dedicated right-of-way. A case study is performed for the intersection of Van Voorhis Road and Chestnut Ridge Road in Morgantown, West Virginia, along the WV-705 corridor. Simulation results from VISSIM show that the triangabout design can reduce travel delay by 50% compared with the existing configuration. Also, the number of conflict points compared with a conventional intersection is reduced by 34%. There are a number of qualitative benefits of this design compared with conventional intersections at an L-shaped corridor vertex.