Citation

Robinson B, Rodegerdts L. Transp. Res. Circular 2000; (E-C018): 422-433.

Copyright

(Copyright © 2000, U.S. National Academy of Sciences Transportation Research Board)

DOI

unavailable

PMID

unavailable

Abstract

The U.S. Federal Highway Administration (FHWA) publication, "Roundabouts: An Informational Guide," presents a comprehensive discussion of roundabout planning, performance analysis, and design. One of its features is the definition of six categories of roundabouts, ranging from small, urban mini-roundabouts to relatively large, rural double-lane roundabouts. Distinctions have been made between the various categories in terms of characteristics, planning procedures, operational analysis, and design treatments. This paper presents the various elements of operational analysis included in the guide, including measures of capacity and performance analysis, and provides a discussion of many of the decisions made during the development of the guide. The paper presents capacity curves for urban compact roundabouts, single-lane roundabouts, and double-lane roundabouts, as well as adjustment factors to account for the effect of short lanes (flaring). The paper also presents the methodologies and recommended practices for determining degree of saturation, delay, and queuing.