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TRB’s National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide – Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts.

This report updates the U.S. Federal Highway Administration’s Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.


Equation 6-3 on page 6-58 incorrectly contains an addition sign (+) as an operator. The correct operator should be a subtraction sign (-).

Errata #2

Exhibit 5-23 on page 5-29 of NCHRP Report 672 contains an incorrect calculation of estimated injury crashes.

There is a summary document, Paths to Practice, available.

Suggested Citation

National Academies of Sciences, Engineering, and Medicine. 2010. Roundabouts: An Informational Guide – Second Edition. Washington, DC: The National Academies Press.

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Publication Info

396 pages |  8.5 x 11 |  DOI:

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