Roundabout practices
By: Alek Pochowski, Andy Paul, and Lee A. Rodegerdts
Contributors: Paul, Andy, author; Rodegerdts, Lee A. (Lee August), 1970- author; National Research Council (U.S.). Transportation Research Board; National Cooperative Highway Research Program; American Association of State Highway and Transportation Officials; United States. Federal Highway Administration
Series: NCHRP synthesis -- 488; Synthesis of highway practice -- no. 488.
Publisher: Transportation Research Board
Published: 2016
Place of publication: Washington, D.C
Language: eng
Number of pages: 81
ISBN-13: 9780309272087; 9781523108848
Subjects: Traffic circles; Roads; Interchanges and intersections; Carrefours giratoires; Routes; Entretien et réparations
Description: As of 2013, there were an estimated 3,200 roundabouts in use throughout the country. This synthesis documents and summarizes roundabout policies, guidance, and practices in place within state departments of transportation (DOTs) as of 2015. The primary focus of the synthesis is on roundabout selection and design with a secondary focus on performance analysis. Information used in this study was gathered through a literature review and a survey of state DOTs. Personnel from seven states were interviewed to create case examples and more specific information. Among the findings, the primary reason cited for the selection of roundabouts is improved safety performance compared with other intersection options, followed by shorter vehicular delays and higher capacity. Planning-level cost estimates (screening or feasibility level estimates) for mini-, single-lane, and multilane roundabouts ranged from $249,000 to $2.05 million. The majority of reporting states have developed some public education materials to support roundabout projects, such as websites, videos, and flyers and/or pamphlets. To analyze roundabout performance, about three-quarters of the reporting states use some form of the Highway Capacity Manual 2010 model and SIDRA's Standard Model. Most of the reporting states analyze safety performance at roundabouts, using crash modification factors, crash reduction factors, and/or the Highway Safety Manual predictive methodology. Most states use a design life of 20 years when developing the ultimate roundabout design. However, the majority uses a phased implementation approach.
Notes: At head of title: National Cooperative Highway Research Program.

"A synthesis of highway practice."

Includes bibliographical references (pages 34-37).

Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Adminisitration! Project 20-05, topic 46-02

"TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 488: Roundabout Practices summarizes roundabout policies, guidance, and practices within state departments of transportation (DOTs) as of 2015. The synthesis may be used as a reference for state agencies that are creating or updating their roundabout and intersection control policies.-- Publisher's description
Table of contents: title: Summary; title: chapter 1. Introduction; title: chapter 2. Literature review; title: chapter 3. Survey results; title: chapter 4. Case examples of roundabout practices; title: chapter 5. Conclusions and suggestions.