Introduction of the Dual–System Urban Interchange Design

The new unconventional dual-system urban interchange (DSUI) design has the potential to improve interchange operations and provide additional access capacity to barrier-separated general purpose (GP) and managed-lane systems. Servicing both GP and managed-lane systems at one cross-street interchange location by using conventional interchange design has been viewed as difficult to construct geometrically, and conventional design also introduces undesirable operational issues. The DSUI design includes a system of one-way frontage roads parallel to the freeway facility that is used to manage traffic flows through a series of coordinated signalized intersections. Ramps to and from these frontage roads serve both the GP and managed-lane systems, providing both systems with either direct or indirect interchange access to a common cross street. The DSUI design was developed for a particular interchange location as part of a managed-lane project in Atlanta, Georgia, and has been viewed as a win–win solution by both the corridor design team and community stakeholders. The design has been shown to improve travel time and mobility measures of effectiveness for the corridor compared with other interchange alternatives, and it provides acceptable traffic operations through the project design-year life. To date, the DSUI design concept has been shown to be a viable interchange alternative that could be considered in other managed-lane corridor studies where managed-lane and GP lane access is desired at the same cross street.