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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

Procedures for Setting Advisory Speeds on Curves

fhwasa1122.pdf (2.53 MB)

June 2011




The contents of this handbook reflect the views of the authors, who are responsible for the facts and the accuracy of the data published herein. The contents do not necessarily reflect the official view or policies of the Federal Highway Administration (FHWA). This handbook does not constitute a standard, specification, or regulation. It is not intended for construction, bidding, or permit purposes. The engineer in charge of the project was Robert Milstead, P.E. #17172 (Maryland).


The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this handbook.


The report that led to the development of this handbook was sponsored by the Texas Department of Transportation and the Federal Highway Administration. The research report was written by Dr. James Bonneson, Mr. Michael Pratt, Mr. Jeff Miles, and Dr. Paul Carlson (1). These researchers are employees with the Texas Transportation Institute (TTI).

1. Report No.


2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Procedures for Setting Advisory Speeds on Curves

5. Report Date

June 2011

6. Performing Organization Code

7. Author(s)

R. Milstead, X. Qin, B. Katz, J. Bonneson, M. Pratt, J. Miles, and P. Carlson

8. Performing Organization Report No.

9. Performing Organization Name and Address

Brudis & Associates, Inc.
Science Applications International Corporation
Texas Transportation Institute

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

US Department of Transportation - Federal Highway Administration
FHWA Office of Safety
1200 New Jersey Avenue, SE
Washington DC 20590

13. Type of Report and Period Covered

October 2009 – June 2011

14. Sponsoring Agency Code

15. Supplementary Notes

Project performed for the Federal Highway Administration
Project Title: Curve Advisory Speed Workshops and Demonstrations
Project Manager: Guan Xu
FHWA Technical Panel: Ed Rice, Richard Knoblauch, Kevin J. Sylvester, Joseph Cheung

16. Abstract

Horizontal curves are a necessary component of the highway alignment; however, they tend to be associated with a disproportionate number of severe crashes. Warning signs are intended to improve curve safety by alerting the driver to a change in geometry that may not be apparent or expected. However, several research projects conducted in the last 20 years have consistently shown that drivers are not responding to curve warning signs or complying with the Advisory Speed plaque. It is estimated that half of all speeding related roadway departure crashes occur on curves. One of the reasons that curves are overrepresented in speeding related fatalities is due, in part, to advisory speeds that are not consistent, and therefore, not credible.

A project by Texas Transportation Institute (TTI), Texas Research Project 0-5439 "Identifying and Testing Effective Advisory Speed Setting Procedures", exemplifies how current procedures for setting advisory speed on curves are not reliable, and has developed new criteria and a new procedure that are more consistent with driver expectation. The new procedure involves the use of an Excel spreadsheet and a handbook for applying the new criteria.
The procedures described in the handbook are intended to improve consistency in advisory speed signing and, hopefully, driver compliance with the advisory speed. The handbook describes; 1) guidelines for determining when an advisory speed is needed; 2) criteria for identifying the appropriate advisory speed; 3) an engineering study method for determining the advisory speed; and 4) guidelines for selecting other curve related traffic control devices.

17. Key Words

Traffic Control Devices, Warning Signs, Speed Signs, Highway Curves, Speed Measurement, Trucks, Traffic Speed

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.