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FHWA Highway Safety Programs

Methods and Practices for Setting Speed Limits: An Informational Report

fhwasa12004.pdf (7.27 MB)

(Note: This document has been converted from the original publication to 508-compliant HTML. The formatting has been adjusted for 508 compliance, but all the original text content is included, plus additional text descriptions for the images, photos and/or diagrams have been provided below.)

Cover artwork. Please see Extended Text Description below.

(Extended Text Description: Cover artwork for the publication "Methods and Practices for Setting Speed Limits: An Informational Report." The cover includes photos in the center of the design, depicting various speed limit signs in different environments. The first photo (on the left, center, and larger than the other photos) has a speed limit sign that reads "Speed Limit 30", next to a two-lane road running through a forest in the fall. The second photo shows a "Speed Limit 45" sign with a blue sky and a few clouds behind it. The third photo shows "Speed Limit 25" next to a road in a suburban area with green trees and grass. Under the photos is the text "FHWA Safety Program." At the bottom of the cover design are three logos, from left to right: The US Department of Transportation - Federal Highway Administration logo, the ITE - Institute of Transportation Engineers logo, and the Safe Roads for a Safer Future - Investment in roadway safety saves lives logo. In the bottom left corner is the text "FHWA-SA-12-004" and in the bottom right corer is the website link http://safety.fhwa.dot.gov.)

Disclaimer

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.

Notice

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.

Acknowledgments

Gerald J. Forbes (F) served as the ITE Project Consultant and the overall technical editor for this report. He was responsible for the technical content and developing the case studies.

This report was based on a draft report, Best Practices for Setting Rational Speed Limits, prepared by Vanasse Hangen Brustlin, Inc. for the Federal Highway Administration, Office of Safety in May, 2009. Westat and Raghavan Srinivasan assisted in the development of the FHWA draft report.

ITE would like to acknowledge the following individuals who supplied information or provided comments in the development of this informational report:

Tony S. Abbo (M)
Richard F. Beaubien (F)
Leanna M. Belluz (M)
Robert Bucholc
Harry A. Campbell (F)
Tom Carmody
Christopher J. Dack (F)
Chris C. Day (M)
Andrew W. Edgar (M)
James W. Ellison (F)
John E. Fisher (F)
Kay Fitzpatrick (F)
Jenny L. Grote (F)
Abdullah J. Habibzai
Lawrence T. Hagen (F)
Wen Hu (M)
Kenton R. Jones
Arash Khoshghalb (M)
Chris King
Ryan C. Kump (M)
Greg M. Laragan (F)
Matthew P. Lawrie (M)
Mark A. Madden (M)
Sean P. Merrell (M)
Rock E. Miller (F)
Craig S. Neustaedter (F)
Michael D. Nichols (M)
Kwabena Ofosu (M)
Martin R. Parker Jr. (M)
Veronica Pelkey
Eduardo A. Petil (M)
William B. Raffensperger (M)
Lawrence E. Sefcik
Douglas A. Skowronek (M)
Harry W. Thompson (F)
Blair Turner
Elia Twigg
David C. Woodin (F)
Peter J. Yauch (F)
Erik H. Zandvliet (M)

ITE would like to acknowledge the ITE Traffic Engineering Council technical committee members who reviewed and provided comments on this report:

Gerald J. Forbes (F), Chair
Geni B. Bahar (M)
Marcus A. Brewer (M)
Wen Cheng (M)
John A. Davis (F)
Melisa D. Finley (M)
Paul Mackey (M)
Richard J. Porter (M)
Keith B. Rohling (M)
Kelly I. Schmid (M)
Rick J. Staigle (M)
James E. Tobaben (F)
John W. Van Winkle (M)

ITE would also like to acknowledge the Federal Highway Administration staff that reviewed and provided comments on this report:

Guan Xu (M), FHWA Project Manager
Craig Allred
James E. (Eric) Ferron (M)
Michael S. Griffith (M)

Note: Letters in parentheses indicate ITE member grade: M—Member, F—Fellow.

 

Technical Report Documentation Page

1. Report No.

FHWA-SA-12-004

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Methods and Practices for Setting Speed Limits: An Informational Report

5. Report Date

April 2012

6. Performing Organization Code

7. Authors

Gerald J. Forbes, P.Eng.
Teresa Gardner, P.E.
Hugh McGee, P.E., Ph.D.
Raghavan Srinivasan, Ph.D.

8. Performing Organization Report No.

9. Performing Organization Name and Address

Institute of Transportation Engineers
1627 Eye Street, NW, Suite 600
Washington, DC 20006

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

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

13. Type of Report and Period Covered

April 2011-April 2012

14. Sponsoring Agency Code

15. Supplementary Notes

FHWA Project Manager: Guan Xu
FHWA Technical Panel: Craig Allred, Eric Ferron, Michael Griffith
ITE Project Manager: Lisa Fontana Tierney

16. Abstract

This informational report describes four primary practices and methodologies that are used in establishing speed limits (engineering approach, expert systems, optimization, and injury minimization). It also reviews the basic legalities of speed limits and presents several case studies for setting speed limits on a variety of roads.

Despite the general acceptance and wide-spread use of speed limits throughout the world, there has been no consensus among practitioners concerning the methods and techniques that should be used to select the most appropriate speed limit for a particular facility. At the current time, it appears unlikely that any consensus will be achieved in the near future. This leaves practitioners without definitive guidance on this important issue, and in search of information to assist them. This report provides the information necessary for practitioners to make informed decisions in selecting a method for setting speed limits in their jurisdiction.

This report presents the procedures that highway agencies can and do use to set speed limits. As an informational report it provides a broad overview of the different speed limit setting methods that are available for use, but it makes no specific policy recommendations or suggestions.

Special situations, such as advisory, school zone, and work zone speeds are discussed. Speed limit enforcement and reevaluation of speed limits are discussed briefly. The design speed for the roadway will not be discussed, except as it may relate to the setting of speed limits. This is because design speed is a characteristic of the roadway that is essentially "built-in" to the road, and is not easily modified.

17. Key Words

Speed Limits, Traffic Control Devices, Speed Signs, Speed Measurement, Speed Study Data Collection, Speed Limit Enforcement, Statutory Speed

18. Distribution Statement

No restrictions.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No of Pages 22. Price

107 N/A

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

 

SI* (Modern Metric) Conversion Factors

Approximate Conversions to SI Units

Symbol

When You Know

Multiply By

To Find

Symbol

Length

in

inches

25.4

millimeters

mm

ft

feet

0.305

meters

m

yd

yards

0.914

meters

m

mi

miles

1.61

kilometers

km

Area

in2

square inches

645.2

square millimeters

mm2

ft2

square feet

0.093

square meters

m2

yd2

square yard

0.836

square meters

m2

ac

acres

0.405

hectares

ha

mi2

square miles

2.59

square kilometers

km2

Volume

fl oz

fluid ounces

29.57

milliliters

mL

gal

gallons

3.785

liters

L

ft3

cubic feet

0.028

cubic meters

m3

yd3

cubic yards

0.765

cubic meters

m3

NOTE: volumes greater than 1000 L shall be shown in m3

Mass

oz

ounces

28.35

grams

g

lb

pounds

0.454

kilograms

kg

T

short tons (2000 lb)

0.907

megagrams (or "metric ton")

Mg (or "t")

Temperature (exact degrees)

oF

Fahrenheit

5 (F-32)/9 or (F-32)/1.8

Celsius

oC

Illumination

fc

foot-candles

10.76

lux

lx

fl

foot-Lamberts

3.426

candela/m2

cd/m2

Force and Pressure or Stress

lbf

pound force

4.45

Newtons

N

lbf/in2

pound force per square inch

6.89

kilopascals

kPa

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.
(Revised March 2003)

 

Approximate Conversions from SI Units

Symbol

When You Know

Multiply By

To Find

Symbol

Length

mm

millimeters

0.039

inches

in

m

meters

3.28

feet

ft

m

meters

1.09

yards

yd

km

kilometers

0.621

miles

mi

Area

mm2

square millimeters

0.0016

square inches

in2

m2

square meters

10.764

square feet

ft2

m2

square meters

1.195

square yards

yd2

ha

hectares

2.47

acres

ac

km2

square kilometers

0.386

square miles

mi2

Volume

mL

milliliters

0.034

fluid ounces

fl oz

L

liters

0.264

gallons

gal

m3

cubic meters

35.314

cubic feet

ft3

m3

cubic meters

1.307

cubic yards

yd3

Mass

g

grams

0.035

ounces

oz

kg

kilograms

2.202

pounds

lb

Mg (or "t")

megagrams (or "metric ton")

1.103

short tons (2000 lb)

T

Temperature (exact degrees)

oC

Celsius

1.8C+32

Fahrenheit

oF

Illumination

lx

lux

0.0929

foot-candles

fc

cd/m2

candela/m2

0.2919

foot-Lamberts

fl

Force and Pressure or Stress

N

Newtons

0.225

pound force

lbf

kPa

kilopascals

0.145

pound force per square inch

lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.
(Revised March 2003)