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Publication Number: FHWA-HRT-10-024
Date: April 2010

Development of a Speeding-Related Crash Typology

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FOREWORD

The overall goal of the Federal Highway Administration's (FHWA) Speed Management Strategic Initiative and the FHWA Speed Management Program is to improve the safety of the Nation's highways through the reduction of speeding and speed–related (SR) crashes.

This report summarizes a detailed examination of crash data and the development of an SR crash typology. This typology is intended to help identify the crash, vehicle, and driver characteristics that are associated with SR crashes. The goal was to determine several variables associated with SR crashes–such as what, where, when, and who–in order to aid in the development of new treatments/countermeasures and to more effectively target existing treatments. Two large national databases (the Fatality Analysis Reporting System (FARS) and the National Automotive Sampling System General Estimates System (NASS GES)) and two State databases (North Carolina and Ohio) were analyzed using single–variable table analysis and classification and regression tree (CART) analyses.

This document will be useful to traffic engineers as well as city, State, and local officials who are responsible for highway design and public safety.

Monique 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.

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–10–024

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

Development of a Speeding-Related Crash Typology

5. Report Date

April 2010

6. Performing Organization Code

N/A

7. Author(s)

Forrest M. Council, Martine Reurings, Raghavan Srinivasan, Scott Masten, and Daniel Carter

8. Performing Organization Report No.

N/A

9. Performing Organization Name and Address

The University of North Carolina
Highway Safety Research Center
730 Martin Luther King, Jr. Blvd.
Chapel Hill, NC 27599–3430

10. Work Unit No. (TRAIS)

N/A

11. Contract or Grant No.

DTFH61–06–C–00013

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 Task Report,

September 2006–September 2008

14. Sponsoring Agency Code
15. Supplementary Notes

The Contracting Officer's Technical Representative (COTR) was Carol Tan, HRDS–06.

16. Abstract

Speeding, the driver behavior of exceeding the posted speed limit or driving too fast for conditions, has consistently been estimated to be a contributing factor to a significant percentage of fatal and nonfatal crashes. The U.S. Department of Transportation has instituted the Speed Management Strategic Initiative to seek more effective ways to manage the crash–related effects of speeding. In support of this initiative, this study conducted a detailed examination of recent crash data through the development of a speeding–related (SR) crash typology to help define the crash, vehicle, and driver characteristics that appear to result in a higher probability of SR crashes. Thus, the goal is to determine variables associated with SR crashes–such as what, where, when, and who–in order to provide guidance to the future development of new treatments and to more effectively target new and existing treatments. Recent Fatality Analysis Reporting System (FARS) and National Automotive Sampling System General Estimates System (NASS GES) data were used to answer these questions. Because these national databases only allow the use of a definition of SR that combines both exceeding the speed limit and too fast for conditions, two State databases (North Carolina and Ohio) were used to determine if different findings resulted from using the combined definition versus the exceeding the speed limit definition.

Two analysis methodologies were used: (1) single–variable table analysis and (2) classification and regression tree (CART). In the first, for a series of both crash–related and vehicle/driver–related variables (e.g., crash type and age of driver), individual codes within each variable were examined to determine which showed an overrepresentation of SR crashes or SR vehicles/drivers (e.g., rear–end crashes for 16–19–year–old drivers). The second method involved CART analyses which automatically define which factors/variables are the most critical with regard to SR crashes or drivers and which combinations of variables/codes are the most important. Similar single–variable and CART analyses were also conducted for five high–priority subsets of the data (e.g., pedestrian crashes and intersection crashes). As might be expected, the results differed between fatal and total crashes, national and State, and among States. Few differences were seen in the results based on the two definitions. The single–variable table results were consistent with two earlier studies in indicating higher SR percentages in single–vehicle crashes, rural crashes, crashes on curves, nighttime crashes, motorcycle crashes, as well as crashes involving young drivers, male drivers, drivers not using restraints, and drivers under the influence of alcohol. No consistent pattern of speeding was seen in either pedestrian or bicycle crashes or in work zone crashes. The CART results from the different databases were less consistent and more difficult to interpret. The crash–based results consistently identified single–vehicle crashes during adverse weather as a high–priority subgroup. The vehicle–based findings indicated almost no consistency across databases, with young male showing up more than other descriptors.

17. Key Words

Speed, Speeding, Crash typology, Traffic safety, HSIS

18. Distribution Statement

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

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

107

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

 


SI* (MODERN METRIC) CONVERSION FACTORS


TABLE OF CONTENTS

INTRODUCTION

PRIOR STUDIES

DATA USED

DEFINITION OF SR CRASHES

OVERVIEW OF ANALYSIS METHODOLOGY

INTERPRETATION OF RESULTS

RESULTS FOR SINGLE–VARIABLE ANALYSES

RESULTS OF CART ANALYSES

SUMMARY AND CONCLUSIONS

APPENDIX: IDENTIFICATION OF CRITICAL FACTORS USING CLASSIFICATION TREES

REFERENCES

 


LIST OF FIGURES

Figure 1. Graph. Frequency of fatal crashes and percentage of total fatal crashes that are SR

Figure 2. Chart. CART SR output for 2005 FARS crashes

Figure 3. Chart. CART SR output for 2005 GES crashes

Figure 4. Chart. CART results for North Carolina crash-based variables using the combined SR definition (2002–2004)

Figure 5. Chart. CART results for North Carolina crash-based variables using the over speed limit SR definition (2002–2004)

Figure 6. Chart. CART results for Ohio crash-based variables using the combined SR definition (2003–2005)

Figure 7. Chart. CART results for Ohio crash-based variables using the over speed limit SR definition (2003–2005)

Figure 8. Chart. CART SR output for 2005 FARS vehicles/drivers

Figure 9. Chart. CART SR output for 2005 GES vehicles/drivers

Figure 10. Chart. CART results for North Carolina vehicle-based variables using the combined SR definition (2002–2004)

Figure 11. Chart. CART results for North Carolina vehicle-based variables using the over speed limit SR definition (2002–2004)

Figure 12. Chart. CART results for Ohio vehicle-based variables using the combined SR definition (2003–2005)

Figure 13. Chart. CART results for Ohio vehicle-based variables using the over speed limit SR definition (2003–2005)

Figure 14. Chart. CART results for FARS pedestrian subset using limited crash–based variables

Figure 15. Chart. CART results for FARS intersection subset using limited crash–based variables

Figure 16. Chart. CART results for GES intersection subset using limited crash–based variables

Figure 17. Chart. CART results for FARS lane departure subset using limited crash–based variables

Figure 18. Chart. CART results for GES lane departure subset using limited crash–based variables

 


LIST OF TABLES

Table 1. The number and percentage of SR and non-SR crashes in GES and FARS (2005)

Table 2. The number and percentage of SR and non-SR crashes in North Carolina (2002–2004) and Ohio (2003–2005)

Table 3. Frequency and number/percentage of SR crashes regarding crash severity in GES

Table 4. Frequency and number/percentage of SR crashes regarding crash severity in North Carolina

Table 5. Frequency and number/percentage of SR crashes regarding crash severity in Ohio

Table 6. Frequency and number/percentage of SR crashes regarding crash location

Table 7. Frequency and number/percentage of SR crashes regarding type of collision

Table 8. Frequency and number/percentage of SR crashes regarding type of collision in North Carolina

Table 9. Frequency and number/percentage of SR crashes regarding type of collision in Ohio

Table 10. Frequency and number/percentage of SR crashes regarding first harmful events

Table 11. Frequency and number/percentage of SR crashes regarding first harmful events in North Carolina

Table 12. Frequency and number/percentage of SR crashes regarding first harmful events in Ohio

Table 13. Frequency and number/percentage of SR crashes regarding nonmotorist involvement

Table 14. Frequency and number/percentage of SR crashes regarding nonmotorist involvement in North Carolina

Table 15. Frequency and number/percentage of SR crashes regarding nonmotorist involvement in Ohio

Table 16. Frequency and number/percentage of SR crashes regarding the location of the first harmful event

Table 17. Frequency and number/percentage of SR crashes regarding the location of the first harmful event in North Carolina

Table 18. Frequency and number/percentage of SR crashes regarding the location of the first harmful event in Ohio

Table 19. Frequency and number/percentage of SR crashes regarding the relationship to the junction

Table 20. Frequency and number/percentage of SR crashes regarding the relationship to the junction in North Carolina

Table 21. Frequency and number/percentage of SR crashes regarding the relationship to the junction in Ohio

Table 22. Frequency and number/percentage of SR crashes regarding functional class

Table 23. Frequency and number/percentage of SR crashes regarding functional class in North Carolina

Table 24. Frequency and number/percentage of SR crashes regarding functional class in Ohio

Table 25. Frequency and number/percentage of SR crashes regarding to speed limit

Table 26. Frequency and number/percentage of SR crashes regarding speed limit in North Carolina

Table 27. Frequency and number/percentage of SR crashes regarding speed limit in Ohio

Table 28. Frequency and number/percentage of SR crashes regarding number of travel lanes

Table 29. Frequency and number/percentage of SR crashes regarding number of travel lanes in North Carolina

Table 30. Frequency and number/percentage of SR crashes regarding number of travel lanes in Ohio

Table 31. Frequency and number/percentage of SR crashes regarding AADT per lane in North Carolina

Table 32. Frequency and number/percentage of SR crashes regarding AADT per lane in Ohio

Table 33. Frequency and number/percentage of SR crashes regarding roadway alignment

Table 34. Frequency and number/percentage of SR crashes regarding roadway alignment in North Carolina

Table 35. Frequency and number/percentage of SR crashes regarding roadway alignment in Ohio

Table 36. Frequency and number/percentage of SR crashes regarding roadway profile

Table 37. Frequency and number/percentage of SR crashes regarding roadway profile in North Carolina

Table 38. Frequency and number/percentage of SR crashes regarding roadway profile in Ohio

Table 39. Frequency and number/percentage of SR crashes regarding work zone

Table 40. Frequency and number/percentage of SR crashes regarding work zone in North Carolina

Table 41. Frequency and number/percentage of SR crashes regarding work zone in Ohio

Table 42. Frequency and number/percentage of SR crashes regarding light condition

Table 43. Frequency and number/percentage of SR crashes regarding light condition in North Carolina

Table 44. Frequency and number/percentage of SR crashes regarding light condition in Ohio

Table 45. Frequency and number/percentage of SR crashes regarding surface condition

Table 46. Frequency and number/percentage of SR crashes regarding surface condition in North Carolina

Table 47. Frequency and number/percentage of SR crashes regarding surface condition in Ohio

Table 48. Frequency and number/percentage of SR crashes regarding weather

Table 49. Frequency and number/percentage of SR crashes regarding weather in North Carolina

Table 50. Frequency and number/percentage of SR crashes regarding weather in Ohio

Table 51. Frequency and number/percentage of SR crashes regarding season

Table 52. Frequency and number/percentage of SR crashes regarding season in North Carolina

Table 53. Frequency and number/percentage of SR crashes regarding season in Ohio

Table 54. Frequency and number/percentage of SR crashes regarding day of the week

Table 55. Frequency and number/percentage of SR crashes regarding day of the week in North Carolina

Table 56. Frequency and number/percentage of SR crashes regarding day of the week in Ohio

Table 57. Frequency and number/percentage of SR crashes regarding driver age

Table 58. Frequency and number/percentage of SR crashes regarding driver age in North Carolina

Table 59. Frequency and number/percentage of SR crashes in relation to driver age in Ohio

Table 60. Frequency and number/percentage of SR crashes regarding drive gender

Table 61. Frequency and number/percentage of SR crashes regarding drive gender in North Carolina

Table 62. Frequency and number/percentage of SR crashes regarding drive gender in Ohio

Table 63. Frequency and number/percentage of SR crashes regarding driver restraint

Table 64. Frequency and number/percentage of SR crashes regarding driver restraint in North Carolina

Table 65. Frequency and number/percentage of SR crashes regarding driver restraint in Ohio

Table 66. Frequency and number/percentage of SR crashes regarding driver distraction

Table 67. Frequency and number/percentage of SR crashes regarding driver distraction in North Carolina

Table 68. Frequency and number/percentage of SR crashes regarding driver distraction in Ohio

Table 69. Frequency and number/percentage of SR crashes regarding driver physical impairment

Table 70. Frequency and number/percentage of SR crashes regarding driver physical impairment in North Carolina

Table 71. Frequency and number/percentage of SR crashes regarding driver physical impairment in Ohio

Table 72. Frequency and number/percentage of SR crashes regarding driver alcohol use

Table 73. Frequency and number/percentage of SR crashes regarding driver alcohol use in North Carolina

Table 74. Frequency and number/percentage of SR crashes regarding driver alcohol use in Ohio

Table 75. Frequency and number/percentage of SR crashes regarding driver drug use

Table 76. Frequency and number/percentage of SR crashes regarding driver drug use in North Carolina

Table 77. Frequency and number/percentage of SR crashes regarding driver drug use in Ohio

Table 78. Frequency and number/percentage of SR crashes regarding prior speeding convictions

Table 79. Frequency and number/percentage of SR crashes regarding license type

Table 80. Frequency and number/percentage of SR crashes regarding license restriction compliance

Table 81. Frequency and number/percentage of SR crashes regarding vehicle type

Table 82. Frequency and number/percentage of SR crashes regarding vehicle type in North Carolina

Table 83. Frequency and number/percentage of SR crashes regarding vehicle type in Ohio

Table 84. Frequency and number/percentage of SR crashes regarding hazardous cargo

Table 85. Frequency and number/percentage of SR crashes regarding hazardous cargo in North Carolina

Table 86. Frequency and number/percentage of SR crashes regarding hazardous cargo in Ohio

Table 87. Characteristics of SR pedestrian crashes

Table 88. Characteristics of SR intersection crashes

Table 89. Characteristics of SR lane departure crashes

Table 90. Characteristics of fatal SR crashes by area type (rural/urban)

 


ABBREVIATIONS

AADT Annual average daily traffic

CART Classification and regression tree

FARS Fatality Analysis Reporting System

FHWA Federal Highway Administration

HSIS Highway Safety Information System

NASS CDS National Automotive Sampling System Crashworthiness Data System

NASS GES National Automotive Sampling System General Estimates System

SR Speeding-related

UDA Unsafe driving act

 

FHWA-HRT-10-024

 

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