Many grade separated intersection forms are in service today across North Carolina. Traditionally, in busy urban and suburban environments with heavy traffic demands on mainline and side street arterial movements, grade separation has taken the form of partial and full cloverleaf designs. This often results in unnecessarily expensive infrastructure being constructed in an arterial environment not meant to provide the free flowing movements you would expect to find in a freeway environment. Current ongoing research by this team is investigating a host of options that could be considered as an alternative to these more traditional designs – designs that very often require a smaller footprint, are likely to be cheaper to construct, and fit within the context of the intersecting roadways. It is anticipated that the results of this ongoing research effort will yield a handful of promising design alternatives the profession can consider under varying traffic demands and right-of-way constraints in a more urbanized environment where two arterials cross.
The findings that will come from this ongoing research effort will be groundbreaking. It is anticipated that many of the designs that will show promise have never been considered or designed in most states. With the vast majority of these designs being so new and atypical, it is anticipated that the NCDOT and practitioners who are asked to sign and mark these sites will have the near impossible task of doing so with little-to-no guidance. Case studies from other states are often hard to track down and are often based on speculation and little, if any, follow-up evaluation. Guidebooks don’t exist on these specific facility types because of the lack of sites. Instead, the engineer more often has to rely on their gut instincts based on similar roadway design features that exist in current, more prominent designs.
This research project aims to take the next step toward designing and constructing at-grade intersections in North Carolina. The objectives of this project are two-fold: 1) provide roadway marking and signing recommendations for unconventional at-grade intersections considered as feasible options based on current ongoing research and 2) determine if any of the sites currently being considered cannot be reasonably signed and/or marked to provide safe passage of motorist, pairing the list down further from the initial sites showing promise from an operational and safety standpoint.