Roundabouts

Roundabouts are circular intersections. Roundabouts reduce traffic conflicts (for example, left turns) that are frequent causes of crashes at traditional intersections. Unlike a traffic circle or a rotary, a roundabout's incoming traffic yields to the circulating traffic.

Technical Implementation & Tools
Research
Resources

Technical Implementation & Tools

Mini-Roundabouts: Technical Summary | Presentation
This technical summary is designed as a reference for State and local transportation officials, Federal Highway Administration (FHWA) Division Safety Engineers, and other professionals who may be involved in the design, selection, and implementation of mini-roundabout intersections.
NCHRP Report 572: Roundabouts in the United States, Transportation Research Board, The National Academies, 2007. [PDF 4.33 MB]
Based on a comprehensive evaluation of roundabouts in the United States, the report presents methods of estimating the safety and operational impacts of roundabouts and updates design criteria for them. The report will be useful to geometric designers and traffic engineers considering improvements to an intersection.
NCHRP Report 674: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities, PDF (8.3 MB)
This report is intended to provide practitioners with useful information related to establishing safe crossings at roundabouts and channelized turn lanes for pedestrians with vision disabilities. The results of this research will be useful to engineers, the accessibility community, policy makers, and the general public to aid in understanding the specific challenges experienced at these facilities by pedestrians with vision disabilities.
Non-visual gap detection at roundabouts by pedestrians who are blind: A summary of the Baltimore roundabouts study
The Access Board Report is a summary of a research project conducted in the Baltimore, Maryland metropolitan area in April, 2000. The study was the first of a series of research projects to be conducted to evaluate access to modern roundabouts by pedestrians who are blind.
Pedestrian Access to Modern Roundabouts: Design and Operational Issues for Pedestrians who are Blind
The proposed description is "Research sponsored by the Access Board, the National Eye Institute, and the American Council of the Blind suggests that some roundabouts can present significant accessibility challenges and risks to the blind user. This report summarizes orientation and mobility techniques used by pedestrians who are blind in traveling independently across streets; highlights key differences between roundabouts and traditional intersections with respect to these techniques; suggests approaches that may improve the accessibility of roundabouts to blind pedestrians; and encourages transportation engineers and planners to implement and test design features to improve roundabout accessibility.
Pedestrian Access to Roundabouts: Assessment of Motorists’ Yielding to Visually Impaired Pedestrians and Potential Treatments To Improve Access, FHWA-HRT-05-080, May 2006. [HTML, PDF 1.14 MB]
NEW Proven Safety Countermeasures
Roundabouts are featured as one of the nine Proven Safety Countermeasures that are the subject of the 2012 Guidance Memorandum on Promoting the Implementation of Proven Safety Countermeasures.
Roundability Accessibility Summit, 2002.
The Roundabout Accessibility Summit brought together stakeholders to address accessibility issues within roundabouts as input to the U.S. Access Board Draft Public Rights of Way Accessibility Guidelines.
Roundabout Fact Sheet, FHWA, CRT, Corporate Research & Technology. Roundabouts are a proven safety solution that prevent and reduce the severity of intersection crashes. Roundabouts are designed to meet the needs of all road users—drivers, pedestrians, pedestrians with disabilities, and bicyclists. A roundabout eliminates some of the conflicting traffic, such as left turns, which cause crashes at traditional intersections. Because roundabout traffic enters or exits only through right turns, the occurrence of severe crashes is substantially reduced. [PDF 59 KB]
Roundabout Outreach and Education Toolbox
This Toolbox is designed to be a highly useable, online reference that connects transportation professionals with outreach resources from across the country to help them obtain public support for roundabouts.
Roundabouts: An Informational Guide, FHWA-RD-00-67, June 2000 [HTML, PDF 344 KB]
Roundabouts: An Informational Guide, Second Edition, PDF (25 MB) | NHI Workshop
Published as NCHRP Report 672, the 2010 edition of the Roundabouts Informational Guide is now available for free download from the TRB website or for purchase from the TRB bookstore (http://books.trbbookstore.org/). The Second Edition was jointly funded by FHWA and NCHRP, and replaces the First Edition as a comprehensive guide to roundabouts planning, design, analysis and operation, now based on more than a decade of U.S. experience. Also, the FHWA National Highway Institute workshop Modern Roundabouts: Intersections Designed for Safety has been updated to reflect the new Guide; please visit the NHI website to learn more.
Roundabouts: Technical Summary | Presentation
This technical summary explores the characteristics of modern roundabouts while reinforcing the need to apply a principles-based approach to design.
Summary Report: An Evaluation of Signing for Three-Lane Roundabouts, March 2010
Signing and marking strategies are important for all types of roundabouts, but the complexities of three-lane roundabouts necessitate additional research and examination of in order to achieve desired lane use confidence and discipline by drivers. The objectives of this study were to identify signing and marking strategies that result in higher levels of comprehension and compliance in lane selection on the approach to roundabouts and to examine the effects of these strategies on lane use after an approach lane has been selected.

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Research

Active Projects

Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities
Roundabouts and channelized turn lanes present challenges different from other intersections for individuals with blindness and visual impairments, because the traffic is most often under yield control as opposed to stop control. Anecdotal evidence indicates that pedestrians with vision impairment sometimes avoid roundabouts and channelized turn lanes by taking a more circuitous route. In addition to determining when to cross the road, pedestrians with vision impairment must identify where to cross, which way to walk during the crossing, and when they have arrived at their destination curb or island. All of these tasks become more difficult for pedestrians with vision impairment at roundabouts and channelized turn lanes. The objective of this research is to recommend a range of geometric designs, traffic control devices, and other treatments that will make pedestrian crossings at roundabouts and channelized turn lanes useable by pedestrians with vision impairment.
Source Organization: National Cooperative Highway Research Program
Project/Contract/Grant Number: 03-78A
Evaluating the Performance and Effectiveness of Roundabouts
The objectives of this project include the following: 1) Determine the impact on crash severity at locations where roundabouts have been installed. 2) Observe roundabout operations including truck maneuvers. 3) Identify the key geometric configurations and site characteristics that influence safety, performance and return on investment.
Source Organization: Michigan Department of Transportation
Project/Contract/Grant Number: 2010-0278 Z2
Evaluating the Performance of Corridors with Roundabouts
Roundabouts are increasingly recognized as an intersection control strategy that can fulfill multiple performance goals related to traffic operation and safety, and meet societal goals related to sustainability, livability, complete streets, context sensitive design, economic development, and others. Some transportation agencies have recently constructed or approved the use of a series of roundabouts on an arterial rather than the traditional solution of coordinated signalized intersections. While there are anecdotal reports suggesting that functionally interdependent roundabouts on a corridor are successful in meeting performance goals, little research has been conducted to determine objectively the efficacy of this alternative as compared to signalized intersections. The performance of traffic signal systems on arterials is well researched and documented, and methods to predict their performance are well established. The objective of this research is to provide traffic engineers, transportation planners, and other practitioners with performance measurement and evaluation methods to evaluate comprehensively the performance of functionally interdependent roundabouts on arterials, thus enabling a comparison with signalized intersections, in order to arrive at a design solution.
Source Organization: National Cooperative Highway Research Program
Project/Contract/Grant Number: 03-100

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Resources

Video

Modern Roundabouts: A Safer Choice, FHWA-SA-10-023 [WMV (109 MB), MOV (510 MB)]
- Transcripts:
  - Audio with speakers
  - Audio without speakers
Note: The Road Commission for Oakland County, Michigan, which contributed footage to this video, was erroneously referenced in the “Acknowledgements” of this DVD as Road Commission of Oakland County, California in an initial version of the DVD that appeared on this website until July 21, 2010. We thank the Road Commission for Oakland County, Michigan for its leadership in improving safety through roundabouts and we apologize for the error. The current version of the DVD is correct.

Presentations

Overview of the Northeast U.S. Roundabouts Peer Exchange
Safety Aspects of Roundabouts
This presentation is on the safety aspects of the modern roundabout.

Publications

State Resources
- A Citizen’s Guide to Roundabouts. (NYSDOT) [PDF 15.26 MB]
- Example Plan Sheets for Typical Single Lane Roundabout. (NYSDOT)
- Kansas Roundabout Guide. A Supplement to FHWA’s Roundabouts: An Informational Guide, October 2003 [PDF 17.71 MB]
  Guide is a supplement to the FHWA document, Roundabouts: An Informational Guide, FHWA-RD-00-067. 2000.
- Interim Reports and (Design) Guidance. (NYSDOT) June 30, 2000. [PDF 136 KB)
- Photograph of Fish Hook Pavement Markings on Approach. (NYSDOT)
- Photograph of View from Multilane Approach Yield Line. (NYSDOT)
- Rodel 1 Interactive Roundabout Design. (NYSDOT) [PDF 1.31 MB]
  RODEL is a fully interactive software program for aiding roundabout design.
- Roundabouts – A Safer Choice (brochure), FHWA-SA-08-006, 2008 [En Español]
- Wisconsin Department of Transportation - Roundabout Guide