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REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number:  FHWA-HRT-14-065    Date:  February 2015
Publication Number: FHWA-HRT-14-065
Date: February 2015

 

Evaluation of Pavement Safety Performance

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Page i, TECHNICAL REPORT
DOCUMENTATION PAGE,
Item 15 for Supplementary Notes
FHWA Contract Task Managers:
Roya Amjadi, Office of Safety Research and Development, and
Jim Sherwood, Office of Infrastructure Research and Development
at Turner-Fairbank Highway Research Center,
6300 Georgetown Pike McLean VA 22101
/publications/research/safety/14065/index.cfm#errata01

 

FOREWORD

The research documented in this report was conducted as part of Phase VI of the Federal Highway Administration (FHWA) Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI–PFS). The FHWA established this pooled fund study in 2005 to conduct research on the effectiveness of the safety improvements identified by the National Cooperative Highway Research Program Report 500 Guides as part of the implementation of the American Association of State Highway and Transportation Officials Strategic Highway Safety Plan. The ELCSI-PFS studies provide a crash modification factor (CMF) and benefit-cost (BC) economic analysis for each of the targeted safety strategies identified as priorities by the pooled fund member states.

The intent of the study was to isolate the effects of various low cost pavement treatments on roadway safety. This was a retrospective study for pavement safety performance, looking back at crash data both before and after treatments were installed. Both flexible and rigid pavement treatments were analyzed, with the majority typically used for pavement preservation or minor rehabilitation purposes. Although state highway agencies recognize that most of these treatments generally improve pavement friction, they are not typically installed explicitly for safety improvement. The one exception is high friction surfacing, which is typically applied as a spot safety treatment. Under this effort, CMFs and BC ratios were developed for various low-cost pavement treatments.

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-14-065

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

Evaluation of Pavement Safety Performance

5. Report Date

February 2015

6. Performing Organization Code
7. Author(s)

David K. Merritt, Craig A. Lyon, Bhagwant N. Persaud

8. Performing Organization Report No.

No.

9. Performing Organization Name and Address

The Transtec Group, Inc.
6111 Balcones Dr.
Austin, TX 78731

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-10-D-0027-T-11004

12. Sponsoring Agency Name and Address

U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue SE, HIPT-20
Washington, DC 20590

13. Type of Report and Period Covered

Final Report
September 2011-November 2013

14. Sponsoring Agency Code

HIPT-20

15. Supplementary Notes

Contracting Officer’s Technical Representative: Roya Amjadi, Turner-Fairbank Highway Research Center, Office of Safety Research and Development, 6300 Georgetown Pike McLean VA 22101; E-Mail: roya.amjadi@dot.gov; Phone: 202-493-3383

FHWA Contract Task Managers:
Roya Amjadi, Office of Safety Research and Development, and
Jim Sherwood, Office of Infrastructure Research and Development
at Turner-Fairbank Highway Research Center,
6300 Georgetown Pike McLean VA 22101
.

16. Abstract

The intent of this study was to isolate the effects of various low-cost pavement treatments on roadway safety. This was a retrospective study of pavement safety performance, looking back at crash data before and after treatments were installed. Both flexible and rigid pavement treatments were analyzed, with the majority typically used for pavement preservation or minor rehabilitation purposes. Although State highway agencies recognize that most of these treatments generally improve pavement friction, they are not typically installed explicitly for safety improvement, with one exception, high-friction surfacing, which is typically applied as a spot safety treatment.

 

The research was conducted as part of Phase VI of the Federal Highway Administration Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS). This pooled fund study (PFS) was established to conduct research on the effectiveness of the safety improvements identified by the National Cooperative Highway Research Program Report 500 guides as part of implementation of the American Association of State Highway and Transportation Officials Strategic Highway Safety Plan. The intent of the work conducted under the various phases of the ELCSI-PFS is to provide a crash modification factor (CMF) and benefit-cost (BC) economic analysis for each of the targeted safety strategies identified as priorities by the PFS States. Under the effort described herein, CMFs and BC ratios were developed for various low-cost pavement treatments.

17. Key Words

pavement safety, low-cost treatment, pavement friction, pavement texture, pavement treatment

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
http://www.ntis.gov

19. Security Classification
(of this report)

Unclassified

20. Security Classification
(of this page)

Unclassified

21. No. of Pages

154

22. Price
Form DOT F 1700.7 Reproduction of completed page authorized

 

SI* (Modern Metric) Conversion Factors

 

TABLE OF CONTENTS

LIST OF FIGURES

Figure 1. Illustration. Key mechanisms of pavement-tire friction
Figure 2. Graph. Pavement texture categories and their effect on surface characteristics (adapted from Henry)
Figure 3. Photo. Microtexture provided by aggregates on an asphalt pavement
Figure 4. Photo. Macrotexture for an asphalt pavement surface (left) and concrete surface from tining (right).
Figure 5. Photo. Placement of thin asphalt overlay (top) and surface texture of new (bottom left) and worn (bottom right) dense graded asphalt surfaces.
Figure 6. Photo. Surface texture of OGFC
Figure 7. Placement of an UTBWC using a self-priming paver (top) and surface texture of an UTBWC (bottom)
Figure 8. Photo. Placement of a chip seal (top) and surface texture of a single layer chip seal (bottom)
Figure 9. Photo. Placement of a slurry seal (top) and surface texture of a cured slurry seal (bottom)
Figure 10. Microsurfacing placement (top) and surface texture of cured microsurfacing treatment (bottom)
Figure 11. Photo. Diamond ground concrete pavement surface.
Figure 12. Photo. Grooved concrete pavement surface (top) and Next Generation Concrete Surface (bottom)
Figure 13. Photo. Micro-milled asphalt pavement surface
Figure 14. Photo. Shotblast asphalt pavement (top) and concrete pavement (bottom)
Figure 15. Photo. Emulsion material is scrubbed into the pavement surface for a scrub seal surface treatment
Figure 16. Photo. Installation of HFS (top) and finished surfaces (bottom)
Figure 17. Equation. Change in safety for a given crash type at a treated site.
Figure 18. Equation. Estimate of the expected number of crashes before treatment
Figure 19. Equation. Estimate of weight
Figure 20. Equation. Estimate of the index of safety effectiveness
Figure 21. Equation. Standard deviation of the estimated index of safety effectiveness
Figure 22. Equation. Model form for Pennsylvania SPFs
Figure 23. Equation. Model form for North Carolina SPFs
Figure 24. Equation. Model form for California SPFs
Figure 25. Equation. Model form for Minnesota SPFs
Figure 26. Photo. Example of wear in wheelpaths over time for chip seal treatments, reducing surface texture and friction
Figure 27. Equation. Estimated number of crashes that would have occurred in the after period with no treatment in the naïve study
Figure 28. Equation. Estimated variance of B in the naïve study
Figure 29. Equation. Estimated CMF in the naïve study.
Figure 30. Equation. Estimated CMF variance in the naïve study
Figure 31. Equation. Estimated number of crashes that would have occurred in the after period with no treatment in the C-G study
Figure 32. Equation. Estimated variance of B in the C-G study
Figure 33. Equation. Estimated CMF in the C-G study
Figure 34. Equation. Estimated CMF variance in the C-G study.
Figure 35. Equation. Annualized cost pavement treatment.
Figure 36. Equation. Model estimated for total crashes on thin HMA treatments on freeways.
Figure 37. Equation. Model estimated for total crashes on OGFC treatments on two-lane roads.
Figure 38. Equation. Model estimated for total crashes on diamond grinding treatments on freeways

LIST OF TABLES

Table 1. Summary of results from NYSDOT skid-accident reduction program analysis
Table 2. Flexible and concrete pavement treatment strategies considered in Phase VI
Table 3. Typical macrotexture depth for various pavement treatments
Table 4. List of potential data collected for treatment sites.
Table 5. Treatment strategies and quantities provided, by State, for asphalt pavements.
Table 6. Treatment strategies and quantities provided, by state, for concrete pavements
Table 7. Summary statistics for Pennsylvania treatment site geometry
Table 8. Summary statistics for Pennsylvania treatment site AADT and crashes
Table 9. Summary statistics for Pennsylvania reference sites.
Table 10. Summary statistics for North Carolina treatment site geometry
Table 11. Summary statistics for North Carolina treatment site AADT and crashes.
Table 12. Summary statistics for North Carolina reference sites
Table 13. Summary statistics for California treatment site geometry
Table 14. Summary statistics for California treatment site AADT and crashes.
Table 15. Summary statistics for California reference sites
Table 16. Summary statistics for Minnesota treatment site geometry
Table 17. Summary statistics for Minnesota treatment site AADT and crashes
Table 18. Summary statistics for Minnesota reference sites
Table 19. SPF parameter estimates and standard errors for Pennsylvania treatment sites.
Table 20. SPF parameter estimates and standard errors for North Carolina treatment sites
Table 21. SPF parameter estimates and standard errors for California treatment sites.
Table 22. SPF parameter estimates and standard errors for Minnesota treatment sites
Table 23. Summary of pilot test results of including climatic data
Table 24. Estimates of CMFs for chip seal treatment
Table 25. Estimates of CMFs for diamond grinding treatment
Table 26. Estimates of CMFs for thin HMA treatment.
Table 27. Estimates of CMFs for open OGFC treatment
Table 28. Estimates of CMFs for grooving treatment
Table 29. Estimates of CMFs for microsurfacing treatment
Table 30. Estimates of CMFs for slurry seal treatment
Table 31. Estimates of CMFs for UTBWC treatment
Table 32. Estimates of CMFs for chip seal treatment for wet-road crashes on two-lane roads by period after treatment.
Table 33. Estimates of CMFs for single and multi-layer chip seal treatment for wet-road crashes (NC and PA only) by period after treatment.
Table 34. Estimates of CMFs for diamond grinding treatment for wet-road crashes on freeways by period after treatment
Table 35. Estimates of CMFs for OGFC treatment for wet-road crashes on freeways and two-lane roads by period after treatment
Table 36. Summary statistics of HFS treatment site data collected
Table 37. Summary statistics of HFS comparison site data collected.
Table 38. Results for the naïve before-after study based on all sites.
Table 39. Results for the before-after C-G study for treatment sites for which comparison sites were available
Table 40. Results of BC analysis for conventional treatment groups with statistically significant crash reductions
Table 41. Results for model for total crashes on thin HMA treatments on freeways
Table 42. Results for model for total crashes on OGFC treatments on two-lane roads
Table 43. Results for model for total crashes on diamond grinding treatments on freeways.
Table 44. Treatment sites by State, part 1
Table 45. Treatment site by State, part 2.

LIST OF ABBREVIATIONS

AADT Average Annual Daily Traffic
AASHTO American Association of State Highway and Transportation
BC Benefit-Cost
Caltrans California Department of Transportation
CDOT Colorado Department of Transportation
C-G Comparison Group (study)
CMF Crash Modification Factor
CMFunction Crash Modification Function
CPI Consumer Price Index
EB Empirical Bayes
ELCSI-PFS Evaluation of Low-Cost Safety Improvements Pooled Fund Study
FHWA Federal Highway Administration
GLM Generalized Linear Modeling
GP Groove Pavement
HFS High-Friction Surfacing
HIS Highway Information System
HMA Hot Mix Asphalt
HSIS Highway Safety Information System
KDOT Kansas Department of Transportation
KTC Kentucky Transportation Cabinet
MDOT Michigan Department of Transportation
MDT Montana Department of Transportation
MnDOT Minnesota Department of Transportation
NCDC National Climatic Data Center
NCDOT North Carolina Department of Transportation
NCHRP National Cooperative Highway Research Program
NYSDOT New York State Department of Transportation
OGAC Open Graded Asphalt Concrete
OGFC Open-Graded Friction Course
PennDOT Pennsylvania Department of Transportation
R-OGAC Rubberized Open Graded Asphalt Concrete
ROR Run-Off Road
RTM Regression to the Mean
SCDOT South Carolina Department of Transportation
SCRIM Sideway-Force Coefficient Routine Investigation Machine
SEAHC Surface Enhancements at Horizontal Curves
SHRP2 Strategic Highway Research Program 2
SPF Safety Performance Function
TDOT Tennessee Department of Transportation
TRIMS Tennessee Information Management System
UTBWC Ultra-Thin Bonded Wearing Course
WisDOT Wisconsin Department of Transportation

 

 

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