Evaluation of Triangabout as Alternative for Intersection with Nonthrough Arterial Movement

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.