Operational Effects of Signalized Superstreets in North Carolina

Arterials across the United States are operating inefficiently and are becoming increasingly congested because of growing traffic demand. Agencies tasked with improving these arterials are running out of good solutions. Superstreets, called restricted crossing U-turns by FHWA, are part of a menu of unconventional arterial designs that may provide promising solutions. Up to this point, little valid information exists on the operational effects of superstreets because study results have been from macroscopic analyses and simulations of hypothetical arterials. The purpose of this research was to determine the operational effects of the superstreet treatment on existing signalized arterials in North Carolina. The operational analysis involved calibrating and validating VISSIM models of three existing signalized superstreets in North Carolina; two isolated intersections and one five-intersection superstreet corridor. After some adjustments, the team produced VISSIM models that provided travel times within an acceptable range of the field data collected. Results from the three calibrated VISSIM models were compared with results from models of equivalent conventional sites at various volume levels with travel time as the primary measure of effectiveness. The superstreet outperformed the conventional design at each location studied and reduced the overall average travel time per vehicle traveling through the intersection. The travel time savings and extra capacity at higher volumes can buy agencies more years of acceptable operation before intersection improvements, or even interchanges, are necessary.