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From Tech Transfer Newsletter, Winter 2006
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Resources from the Transportation Library
Roundabouts
By Rita Evans, Reference Librarian
Institute of Transportation Studies Library
Modern roundabouts are not the old-style traffic circles and rotaries
constructed prior to the 1960s. The improved design and operation of modern
roundabouts can improve traffic flow and generally makes them safer for motor
vehicles than conventional intersections. According to the Federal Highway
Administration, roundabouts are circular intersections with specific design and
traffic control features. Those features include yield control, channelized
approaches and geometric curvature that limits travel speed.
Roundabouts: An Informational Guide
www.tfhrc.gov/safety/00068.htm
FHWA-RD-00-67, June 2000. 268 pages.
This guide is the primary source of information on roundabouts from FHWA and
provides information on designs suitable for a variety of traffic situations.
Chapters cover policy considerations and planning, evaluation procedures for
assessing operational and safety performance, design guidelines, landscaping and
system considerations. The guide makes extensive use of drawings, photographs
and diagrams and includes a glossary and lists of references. Individual
chapters can be downloaded as .pdf files.
Roundabouts
www.dot.ca.gov/hq/oppd/dib/dib80-01.htm
Caltrans Design Information Bulletin Number 80-01
This bulletin describes the additions to and deviations from FHWA's
Roundabouts: An Informational Guide that are to be used when
designing roundabouts on the California State Highway system.
Designing and Operating Safer Roundabouts
Institute of Transportation Engineers and Federal Highway Administration
Chapter 8 in Toolbox on Intersection Safety and Design,
September 2004. Pages 133-165.
This toolbox describes safety issues and documents the reduction in motor
vehicle crashes when roundabouts are installed. It addresses capacity, design
elements, signage and markings, and pedestrian and bicyclist accommodations.
Includes references, a glossary and many illustrations.
Roundabout Design: Safety and Capacity Background Paper
www.aaafoundation.org/pdf/Roundabouts.pdf (PDF, 86.5 KB)
AAA Foundation for Traffic Safety
July 25, 2004, 7 pages.
Provides an overview of design considerations, capacity, conflicts and safety
issues.
Bicycle and Pedestrian Considerations at Roundabouts
www.dot.state.fl.us/ research-center/ Completed_Proj/ Summary_SF/ FDOT_824.pdf
(summary) (PDF, 10 KB)
Florida Department of Transportation
September 2000, 114 pages.
The Florida DOT conducted an extensive literature review and then analyzed data
from roundabouts in Florida to assess their effect on bicyclists and
pedestrians. They found that while roundabouts reduced casualty accident rates
by 68 percent, there was an increase in the number of bicycle accidents. When
designing a roundabout, special consideration needs to be given to the movement
of bicyclists and pedestrians, because roundabouts may be inappropriate in a
location with a high volume of bicyclists and pedestrians.
When Roadway Design Options Are Wide Open, Why Not Build a
Roundabout?
www.iihs.org/sr/pdfs/sr4009.pdf (PDF, 968 KB)
Status Report, Nov. 19, 2005. Pages 1-4.
Roundabouts can improve traffic flow and reduce injury crashes by as much as
75%. Researchers at the Insurance Institute for Highway Safety looked at 10
locations where roundabouts could have been constructed but weren't and
concluded that vehicle delays could have been reduced by 62-74%. Communities are
encouraged to construct roundabouts when an area is developed to reduce costs
and avoid initial community opposition. When roundabouts were constructed in
Vail, Colorado and Clearwater, Florida, the public embraced them.
Roundabout Designs That Work
www.betterroads.com/articles/jul04b.htm
Better Roads, July 2004. Pages 62-65.
Describes how roundabouts can be used to slow traffic and move it efficiently
through intersections while improving safety. A sidebar notes that signage is
very important, especially for multiple-lane roundabouts. Redesign of
roundabouts with improved signing and marking has greatly mitigated problems in
earlier designs.
RoundaboutsUSA
www.roundaboutsusa.com
Contains useful links to news items about roundabouts, background information,
and resources for roundabouts.
Roundabouts
www.k-state.edu/roundabouts/research.htm
Kansas State University, Center for Transportation Research & Training
Kansas has implemented roundabouts in a number of locations. This website
contains links to articles, reports and research projects related to
roundabouts.
Crash Reductions Following Installation of Roundabouts in the United
States
www.dot.state.ny.us/ roundabouts/ files/ insurance_report.pdf
(PDF, 525 KB)
Insurance Institute for Highway Safety, March 2000. 15 pages.
This study presents a regression analysis of crash data for roundabouts. It
notes that crash reductions are primarily attributable to reduced traffic speeds
and elimination of specific types of motor vehicle conflicts that frequently
occur at angular intersections. While roundabouts are a good choice in some
locations, they are not always appropriate in locations with significant
pedestrian and bicyclist activity.
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