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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

Road Diet Informational Guide

rdig.pdf (1.89 MB)

November 2014

Contact: Rebecca Crowe at, 202-507-3699

Technical Report Documentation Page

1. Report No.


2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Road Diet Informational Guide

5. Report Date

November 2014

6. Performing Organization Code

7. Author(s)

Keith Knapp, Brian Chandler, Jennifer Atkinson, Thomas Welch, Heather Rigdon, Richard Retting, Stacey Meekins, Eric Widstrand, and R.J. Porter

8. Performing Organization Report No.

9. Performing Organization Name and Address

11251 Roger Bacon Drive
Reston, VA 20190

Subconsultants: Iowa State University, Sam Schwartz Engineering, University of Utah

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

Contract No. DTFH61-10-D-00024,
Task Order No. T-12-004

12. Sponsoring Agency Name and Address

Federal Highway Administration
Office of Safety
1200 New Jersey Avenue SE
Washington, DC 20590

13. Type of Report and Period Covered

Informational Guide Book
August 2011 to July 2014

14. Sponsoring Agency Code


15. Supplementary Notes

Rebecca Crowe (, Office of Safety Technologies (, served as the Technical Manager for the Federal Highway Administration (FHWA). The following FHWA staff members contributed as technical working group members, reviewers and/or provided input or feedback to the project at various stages: Peter Eun, David Morena, Tamara Redmond, and Jeff Shaw.

16. Abstract

A classic Road Diet converts an existing four-lane undivided roadway segment to a three-lane segment consisting of two through lanes and a center two-way left turn lane (TWLTL). A Road Diet improves safety by including a protected left-turn lane for mid-block left-turning motorists, reducing crossing distance for pedestrians, and reducing travel speeds that decrease crash severity. Additionally, the Road Diet provides an opportunity to allocate excess roadway width to other purposes, including bicycle lanes, on-street parking, or transit stops. This Informational Guide includes safety, operational, and quality of life considerations from research and practice, and guides readers through the decision-making process to determine if Road Diets are a good fit for a certain corridor. It also provides design guidance and encourages post-implementation evaluation.

17. Key Words

Road Diet, four-lane, undivided, three-lane, two-way-leftturn-
lane, cross section, safety, operations,
reconfiguration, queuing.


18. Distribution Statement

No restrictions.

19. Security Classification (of this report)


20. Security Classification (of this page)


21. No of Pages


22. Price


Form DOT F 1700.7 (8-72)
Reproduction of completed page authorized.