The Alternative Intersection and Interchange Informational Report (AIIR) First Edition was published in 2010 by the Federal Highway Administration. It was the first national, public-sector, comprehensive guidebook on the alternative designs which were starting to be built in many states and some other countries. The AIIR contained operational data from simulation experiments and suggested methodologies for planners and engineers to evaluate alternative designs during project processes.
Although it is now considered out of date by many agencies, the AIIR First Edition has been employed by various agencies as a valuable resource for planning and designing AIIs. In North Carolina, the NCDOT has given freedom to transportation professionals to explore new alternatives to conventional roadway designs, and many more AII designs have emerged since 2010. These new AII designs may involve different traffic patterns, which may introduce confusion and create safety hazards for drivers. In addition, it is anticipated that with more AIIs being installed in the central business areas in the near future, there is a need of incorporating methodologies to assess the pedestrian and bicycle quality of service and safety performance at AII designs.
The primary objective of this research is to initiate the process of compiling the AIIR Second Edition that covers a wider range of alternative intersection and interchange (AII) designs, including three facility categories: at-grade intersection, grade-separated intersections, and service interchanges. This report crafted an annotated outline for the forthcoming AIIR second edition based on a state-of-the-practice literature review and expert interviews on AII designs. Specifically, for each AII design, this report presented high-level descriptive information in a standardized format, including salient geometric design features, operational and safety issues, access management, costs, construction sequencing, environmental benefits, and applicability. Finally, this report features a collection of case studies that illustrate the utilization of diverse AII designs in the context of mobility enhancement or safety improvement projects across different land-use scenarios.
