Welcome to the Modern Roundabouts Web site
This Web site serves as one of the definitive sources on Modern Roundabouts and is a complement to the Federal Highway Administration's research project aimed at developing a comprehensive guide to roundabouts design. The results of this project are contained in the book published by FHWA in August 2000; Roundabouts: An Informational Guide.
Roundabouts are a common form of intersection control used throughout the world.
However, many state and local agencies throughout the United States have been hesitant
to install roundabouts due to a lack of objective nationwide guidelines on planning,
performance, and design.
Prior to the development of Roundabouts: An Informational Guide, the few state and local agencies interested in roundabouts had to rely on foreign roundabout design guides, roundabout proponents, or in some states, statewide roundabout design guides. Roundabouts require strict conformance to standard practice to ensure safe, optimal operation, and this scattered approach to design can lead to inconsistencies at a national level which are consequential in terms of driver expectation and safety. To address this national need, the Federal Highway Administration selected a worldwide team of experts to develop Roundabouts: An Informational Guide.
Roundabouts: An Informational Guide addresses the following topics:
- Definition of a roundabout and what distinguishes roundabouts from traffic circles;
- Methodology for identifying appropriate sites for roundabouts and the range of conditions for which roundabouts offer optimal performance;
- Methodology for estimating roundabout capacity and delay;
- Design principles and standards to which roundabouts should conform, including applicable national standards such as the AASHTO Policy on Geometric Design of Highways and Streets and the Manual on Uniform Traffic Control Devices;
- Consideration for all modes, including heavy vehicles, buses, fixed route transit, bicycles, and pedestrians;
- Guidelines for operational features such as signing, pavement markings, illumination, and landscaping;
- Public acceptance and legal issues associated with roundabouts.
- A database of currently operating or planned roundabouts. You can search the current records in the database or add new sites that are not yet listed.
- An outline of Roundabouts: An Informational Guide.
- A listing of other resources on roundabouts, including articles, papers, books, design guides, and videotapes.