U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content
FacebookYouTubeTwitterFlickrLinkedIn

Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

 
REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number:  FHWA-HRT-13-077    Date:  January 2014
Publication Number: FHWA-HRT-13-077
Date: January 2014

 

Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways

PDF Version (1.89 MB)

HTML Version of Errata for FHWA-HRT-13-077

PDF version of Errata

PDF files can be viewed with the Acrobat® Reader®

The following changes were made to the document after publication:

Location Corrected Values URL
Page i, Block 21 68 /publications/research/safety/13077/index.cfm#errata01
Page 4, SAFETY EFFECTS OF HORIZONTAL ALIGNMENT, Paragraph 1, Sentence 1, Line 2 shown in figure 2 /publications/research/safety/13077/002.cfm#errata02
Page 4, SAFETY EFFECTS OF HORIZONTAL ALIGNMENT, Paragraph 1, Sentence 1, Figure 2 N = [1.55 (LC)(V) + 0.014(D)(V) − 0.012(S)(V)](0.978)W − 30 /publications/research/safety/13077/002.cfm#errata03
Page 5, Paragraph 3, Sentence 2 shown in figure 3: /publications/research/safety/13077/002.cfm#errata04
Page 5, Paragraph 6, Sentence 1 as shown in figure 4: /publications/research/safety/13077/002.cfm#errata05
Page 8, Paragraph 1, Sentence 10 [A = abs(G1 – G2 )] /publications/research/safety/13077/003.cfm#errata06
Page 9, DESCRIPTIVE STATISTICS, Paragraph 1, Sentence 1 [million vehicle miles traveled in the 6-year period (MVMT)] /publications/research/safety/13077/003.cfm#errata07
Page 14, Paragraph 2, Bullet 2 [this is a standard analysis of variance (ANOVA) using an NB distribution and a log link] /publications/research/safety/13077/004.cfm#errata08
Page 16, Paragraph 2, Sentence 1 shown in figure 6 and figure 7 /publications/research/safety/13077/004.cfm#errata09
Page 16, Paragraph 4, Bullet 1,Sentence 2 shown in figure 8 /publications/research/safety/13077/004.cfm#errata10
Page 17, Horizontal Curves and Tangents on Straight Grades, Paragraph 1,Sentence 1, Bullet 1 [number of roadway segments (N) = 8,095 and total roadway length = 595 mi] /publications/research/safety/13077/004.cfm#errata11
Page 17, Horizontal Curves and Tangents on Straight Grades, Paragraph1, Sentence 1 (i.e., number of roadway sections; total roadway length; and minimum, maximum, mean, and median values for specific parameters) /publications/research/safety/13077/004.cfm#errata12
Page 18, Paragraph 1, Sentence 1 shown in figure 10 and figure 11 /publications/research/safety/13077/004.cfm#errata13
Page 20, Paragraph 5, Sentence 1 shown in figure 12, figure 13, and figure 14 /publications/research/safety/13077/004.cfm#errata14
Page 23, Paragraph 1, Sentence 1 shown in figure 16 and figure 17 /publications/research/safety/13077/004.cfm#errata15
Page 25, Paragraph 2, Sentence 1 shown in figure 18 and figure 19 /publications/research/safety/13077/004.cfm#errata16
Page 26, Paragraph 1, Sentence 2 shown in figure 20 and figure 21 /publications/research/safety/13077/004.cfm#errata17
Page 28, Paragraph 1, Sentence 1 shown in figure 23 and figure 24 /publications/research/safety/13077/004.cfm#errata18
Page 29, Paragraph 5, Sentence 1 shown in figure 25 and figure 26 /publications/research/safety/13077/004.cfm#errata19
Page 30, Paragraph 2, Sentence 3 shown in figure 27 and figure 28 /publications/research/safety/13077/004.cfm#errata20
Page 32, Paragraph 1, Sentence 1 shown in figure 30 and figure 31 /publications/research/safety/13077/004.cfm#errata21
Page 33, Paragraph 4, Sentence 1 shown in figure 32 and figure 33 /publications/research/safety/13077/004.cfm#errata22
Page 36, Paragraph 1, Sentence 1 shown in figure 35 and figure 36 /publications/research/safety/13077/004.cfm#errata23
Page 37, Paragraph 4, Sentence 1 shown in figure 37 and figure 38 /publications/research/safety/13077/004.cfm#errata24
Page 39, HORIZONTAL CURVES AND TANGENTS ON STRAIGHT GRADES, Paragraph 1, Sentence 1 shown in figure 39 and figure 40 /publications/research/safety/13077/005.cfm#errata25
Page 42, HORIZONTAL CURVES AND TANGENTS AT TYPE 1 CREST VERTICAL CURVES, Paragraph 1, Sentence 1 shown in figure 43 and figure 44 /publications/research/safety/13077/005.cfm#errata26
Page 44, HORIZONTAL CURVES AND TANGENTS AT TYPE 1 SAG VERTICAL CURVES, Paragraph 1, Sentence 1 shown in figure 47 and figure 48 /publications/research/safety/13077/005.cfm#errata27
Page 46, HORIZONTAL CURVES AND TANGENTS AT TYPE 2 CREST VERTICAL CURVES, Paragraph 1, Sentence 1 shown in figure 51 and figure 52 /publications/research/safety/13077/005.cfm#errata28
Page 48, HORIZONTAL CURVES AND TANGENTS AT TYPE 2 SAG VERTICAL CURVES, Paragraph 1, Sentence 1 shown in figure 55 and figure 56 /publications/research/safety/13077/005.cfm#errata29
Page 50, CMFs FOR COMBINED CRASH SEVERITY LEVELS, Paragraph 1, Sentence 3 shown in figure 59 /publications/research/safety/13077/005.cfm#errata30

 

Report - FHWA-HRT-13-077 Summary Report - FHWA-HRT-13-078 Excel Calcuator Tool - HRTM 2130

 

FOREWORD

The first edition of the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) provides crash modification factors (CMFs) for the safety effects of horizontal curvature and percent grade on rural two-lane highways.(1) However, the HSM does not provide a method to account for the interactions between these effects. Researchers have always presumed that there are interactions between the safety effects of horizontal and vertical alignment, but this has not been demonstrated for specific alignment combinations in a form useful for safety prediction.

This document is a final report highlighting research undertaken to quantify the safety effects of five specific combinations of horizontal and vertical alignment for rural two-lane highways. The research is based on data from the Federal Highway Administration’s Highway Safety Information System (HSIS) for Washington State, including roadway characteristics, horizontal and vertical alignment, traffic volume, and crashes. The outcome is a set of safety prediction models for fatal and injury and property damage only crashes. CMFs representing safety performance relative to level tangents on rural two-lane highways were developed from the models for each of the five combinations of horizontal and vertical alignment to present the results in a form suitable for incorporation in the HSM. This report should be of interest to safety engineers and planners as well as other AASHTO HSM users.

Monique R. Evans
Director, Office of Safety
Research and Development

 

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

 

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.

FHWA-HRT-13-077

2. Government Accession No. 3 Recipient's Catalog No.
4. Title and Subtitle

Safety Effects of Horizontal Curve and Grade Combinations on Rural Two- Lane Highways

5. Report Date

January 2014

6. Performing Organization Code
7. Author(s)

Karin M. Bauer and Douglas W. Harwood

8. Performing Organization Report No.

110785.01.001

9. Performing Organization Name and Address

MRIGlobal
425 Volker Blvd
Kansas City, MO 64110

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-11-C-00050

12. Sponsoring Agency Name and Address

Federal Highway Administration Office of Safety Research and Development 6300 Georgetown Pike McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report December 2010–August 2012

14. Sponsoring Agency Code

 

15. Supplementary Notes

This work was performed under subcontract with the University of North Carolina (UNC) Highway Safety Research Center for Highway Safety Information System (HSIS) under Master Agreement No. 5-555697 Contract No. DTFH61 06 C 000013 and under subcontract for HSIS under Master Agreement No. 5-55771 Contract No. DTFH61 11 C 00050. The UNC Program Manager was David L. Harkey, and the Federal Highway Administration HSIS Program Manager was Carol Tan, Ph.D.

16. Abstract

This report summarizes the results of research undertaken to quantify the safety effects of five types of horizontal and vertical alignment combinations for rural two-lane highways. The research is based on Federal Highway Administration Highway Safety Information System data for Washington State, including crash records from 2003 to 2008. The outcome is a set of safety prediction models for fatal and injury and property damage only crashes.

 

To present the results in a form suitable for incorporation in the American Association of State Highway and Transportation Officials Highway Safety Manual, crash modification factors representing safety performance relative to level tangents were developed from these models for each of the five combinations of horizontal and vertical alignment—horizontal curves and tangents on straight grades, horizontal curves and tangents at type 1 crest vertical curves, horizontal curves and tangents at type 1 sag vertical curves, horizontal curves and tangents at type 2 crest vertical curves, and horizontal curves and tangents at type 2 sag vertical curves.(1)

17. Key Words

Safety, Horizontal curves, Vertical curves, Grade interaction, Crests, Sags, Rural two-lane highways, Crash modeling, Safety performance function, Crash modification factor

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161

19. Security Classification
(of this report)

Unclassified

20. Security Classification
(of this page)

Unclassified

21. No. of Pages

63 68*

22. Price

N/A

Form DOT F 1700.7 Reproduction of completed page authorized

*Modified on November 16, 2014

SI* (Modern Metric) Conversion Factors

TABLE OF CONTENTS

CHAPTER 1—INTRODUCTION

CHAPTER 2—STATE OF KNOWLEDGE LITERATURE REVIEW

CHAPTER 3—DATABASE DESCRIPTION

CHAPTER 4—STATISTICAL ANALYSIS

CHAPTER 5—CRASH MODIFICATION FACTORS

CHAPTER 6—CONCLUSIONS AND RECOMMENDATIONS

REFERENCES

LIST OF FIGURES

LIST OF TABLES

 

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101