New alternative intersection and interchange (AII) designs are being built across the United States to address a myriad of traffic congestion issues.
The National Cooperative Highway Research Program (NCHRP) has begun conducting research studies to understand how these AII’s will impact traffic flow and safety. These new designs sometimes involve reversing traffic lanes from their traditional directions, which may introduce confusion and create safety issues for pedestrians and bicyclists. Pedestrian paths and bicycle facilities may cross through islands or take different routes than expected. These new designs are likely to require additional information for drivers, cyclists, and pedestrians as well as better accommodations for pedestrians and bicyclists, including pedestrians with disabilities.
The objective of NCHRP’s 07-25 research study is to develop a guide for transportation practitioners to improve and integrate pedestrian and bicycle safety considerations at AIIs through planning, design, and operational treatments. Kittelson & Associates recently led a pedestrian and bicycle safety assessment for the North Carolina Department of Transportation (NCDOT) Transportation Mobility and Safety Division (TMSD), in which they applied the NCHRP 07-25 methodology to multiple active projects in the design phase, putting this new guidance into action for North Carolina interchanges and intersections.
The “20 Flag” Method was used to conduct this project. This quantitative analysis method presented in NCHRP Research Report 948 is built around 20 design flags. These flags highlight design characteristics that impact safety and quality of service for people walking and biking regardless of the intersection or interchange type.
Each of the 20 flags includes thresholds for a yellow flag and for a red flag at a given intersection or interchange. A yellow flag is generally associated with user comfort and a red flag with safety. The list is meant to be used both as a comparison tool when selecting between various intersection alternatives as well as guide for practitioners in the design process, highlighting areas of concern. The flags can also be used to indicate where safety countermeasures would be appropriate.
After summarizing the percentage of red flags and percentage of yellow flags of proposed designs, NCDOT was able to raise awareness and identify design recommendations to enhance multimodal safety at several intersections. For at least one project, the quantitative assessment of multiple alternatives helped move forward a design that maximizes multimodal safety.
Throughout April and May of 2022, Quality Counts (QC) worked with the University of North Carolina’s Highway Safety Research Center (HSRC) to collect 26 hours of video over two days at 100 intersections across all corners of North Carolina as part of the research study ‘Validating the NCHRP 7-25 Pedestrian and Bicyclist Quality of Service “20-Flags” Method with Crash Data', awarded through the North Carolina Department of Transportation.
This project presented some challenges for QC. Our team worked with members of the HSRC to collect counts avoiding high school spring breaks, local colleges being release for summer, holidays, and road construction. Robert Berryhill, QC’s Raleigh Operations Manager, worked diligently to ensure the footage delivered provided clear pictures of roadway operations, was filmed during the correct times and was annotated with all the information HSRC needed to fully understand the video they were working with. The video captured will be used by HSRC to perform traffic and pedestrian counts and to be available for further research by the University.
