BACKGROUND: Since its publication in 2010, NCHRP Report 672: Roundabouts: An Informational Guide, Second Edition, has served as a national guide on the different aspects of roundabouts, including planning, analysis, design, and construction. Also during this period, technology changes have taken place, substantial research on the different aspects of roundabouts has been performed, and many roundabouts have been constructed. This research and experience gained from these projects has produced many relevant findings and lessons learned. However, additional research is needed to address the gaps in available roundabout guidance and incorporate the relevant technology, the findings of the new and earlier research, and the lessons learned from the constructed projects into a guide for roundabouts. This guide will provide updated information and guidance on all aspects of roundabouts and help highway agencies and other organizations address relevant issues when considering the planning and implementation of roundabouts.
OBJECTIVE: The objective of this research is to develop a guide that will serve as the primary source for guidance on all aspects of roundabouts. The guide will supersede NCHRP Report 672: Roundabouts: An Informational Guide, and other available guidance on roundabouts.
Phase I: (1) Identify and critically review information relevant to the different aspects of roundabouts (e.g., planning, geometric design, construction, and maintenance). This information may be obtained from published and unpublished sources and contacts with practitioners. (2) Identify and prioritize the weaknesses and gaps in available roundabout guidance based on input from practitioners and other sources. (3) Based on the information gathered in Tasks 1 and 2, propose an updated research plan to be executed in Phase II to develop a guide that addresses all aspects of roundabouts and serves as the primary source for guidance on roundabouts. The plan shall also describe the research proposed to address the gaps identified in Task 2 and include a tentative outline of the proposed guide. Consideration should be given to including case studies demonstrating the performance of roundabouts for different contexts and conditions.
(4) Prepare an interim report that documents the research performed in Phase I and includes the updated research plan for Phase II. Following review of the interim report by the panel, the research team will meet with the project panel. Work on Phase II of the project will not begin until the interim report and the Phase II research plan are approved by the NCHRP.
Phase II: (5) Perform the research approved in Task 4. Prepare a technical memorandum that describes this research and documents the findings that will be incorporated into the guide. Also, update the plan for developing the guide based on these findings. Review comments from NCHRP on this plan shall be incorporated into Task 6. (6) Execute the plan for developing the guide, as modified in Task 5. Based on the results of this work, develop the guide. Also, identify inconsistencies with relevant documents. (e.g., A Policy on Geometric Design of Highways and Streets published by AASHTO and Manual on Uniform Traffic Control Devices published by FHWA). (7) Submit a final deliverable that documents the entire research effort and includes (1) a research report documenting the work performed in the project and used to develop the guide and (2) a stand-alone guide for roundabouts.
TATUS: Research in progress but substantially behind schedule.