National Academies Press: OpenBook

Precision Estimates of AASHTO T 242 (2009)

Chapter: Front Matter

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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Page iii
Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Page vi
Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Page vii
Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2009. Precision Estimates of AASHTO T 242. Washington, DC: The National Academies Press. doi: 10.17226/23017.
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ACKNOWLEDGMENT This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration, and was conducted in the National Cooperative Highway Research Program (NCHRP), which is administered by the Transportation Research Board (TRB) of the National Academies. COPYRIGHT PERMISSION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinion and conclusions expressed or implied in the report are those of the research agency. They are not necessarily those of the TRB, the National Research Council, AASHTO, or the U.S. Government. This report has not been edited by TRB.

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 iii TABLE OF CONTENTS LIST OF TABLES ...................................................................................................................................... v  LIST OF FIGURES ................................................................................................................................... vi  ACKNOWLEDGMENTS ........................................................................................................................ vii  ABSTRACT…… ...................................................................................................................................... viii  CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH ..................................................... 1  1.1  INTRODUCTION ................................................................................................................... 1  1.2  PROBLEM STATEMENT ...................................................................................................... 1  1.3  RESEARCH OBJECTIVE ...................................................................................................... 2  1.4  SCOPE OF STUDY ................................................................................................................. 2  1.5  DATA USED IN STUDY ........................................................................................................ 2  1.5.1  TTI Friction Data ........................................................................................................ 2  1.5.2  TRC Friction Data ....................................................................................................... 3  CHAPTER 2- RESULTS OF ANALYSIS AND ESTIMATES OF PRECISION ................................ 4  2.1  METHOD OF ANALYSIS ...................................................................................................... 4  2.2  ANALYSIS OF TTI FRICTION DATA ................................................................................. 4  2.2.1  Analysis of Initial State System Measurements .......................................................... 4  2.2.2  Analysis of Final State System Measurements ........................................................... 5  2.2.3  Comparison of TTI Initial and Final Precisions .......................................................... 6  2.2.4  Selection of Form of Precision Estimates ................................................................... 6  2.3  ANALYSIS OF TRC FRICTION DATA .............................................................................. 13  2.3.1  Analysis of Arrival State System Measurements ...................................................... 13  2.3.2  Analysis of Departure State System Measurements ................................................. 17  2.3.3  Comparison of TRC Arrival and Departure Precisions ............................................ 25  2.3.4  Selection of Form of Precision Estimates ................................................................. 25  2.4  COMPARISON OF TTI AND TRC PRECISIONS .............................................................. 28  2.5  PRECISION ESTIMATES FOR AASHTO T 242 ................................................................ 29  2.6  COMPARISON WITH CURRENT PRECISION ESTIMATE IN AASHTO T 242 ........... 29  CHAPTER 3- CONCLUSIONS AND RECOMMENDATIONS ......................................................... 30  3.1  CONCLUSIONS .................................................................................................................... 30  3.2  RECOMMENDATIONS ....................................................................................................... 31  3.3  PRECISION STATEMENT FOR AASHTO T 242 .............................................................. 32  REFERENCES …………………………………………………………………………………………..33  APPENDIX A- TTI INITIAL STATE SYSTEM MEASUREMENTS AND THE CORRESPONDING STATISTICS ............................................................................. 34 

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 iv APPENDIX B- TTI FINAL STATE SYSTEM FRICTION MEASUREMENTS AND THE CORRESPONDING STATISTICS ............................................................................. 37  APPENDIX C- TRC ARRIVAL STATE SYSTEM MEASUREMENTS AND THE CORRESPONDING STATISTICS ............................................................................. 47  APPENDIX D- TRC DEPARTURE STATE SYSTEM FRICTION MEASUREMENTS USING 501 TIRE AND THE CORRESPONDING STATISTICS ........................................ 54  APPENDIX E- TRC DEPARTURE STATE SYSTEM FRICTION MEASUREMENTS USING 524 TIRE AND THE CORRESPONDING STATISTICS ........................................ 73 

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 v LIST OF TABLES Table 1-1- Number of friction systems operated at different speeds on various surfaces of the TTI test field ............................................................................................................................................. 3 Table 1-2- Number of friction systems operated at different speeds on various surfaces of the TRC field test ............................................................................................................................................... 3 Table 2-1- Number of data sets, averages, and standard deviations for friction numbers using different TTI measurement systems on three surfaces (Pads) at three speeds .......................................... 5 Table 2-2- Coefficients of variations for friction numbers using TTI measurement systems on three surfaces (Pads) at three speeds ................................................................................................... 5 Table 2-3- Computed F- and critical F- values for comparison of precision estimates for different surfaces of TTI measurements .................................................................................................... 7 Table 2-4- Combined standard deviations for friction numbers of different surfaces (Pads) at TTI ............ 7 Table 2-5- Computed F- and critical F- values for comparison of the precision estimates for different speeds of TTI friction measurements.......................................................................................... 8 Table 2-6- Combined repeatability and reproducibility precisions for frictional properties of TTI measurements ............................................................................................................................. 8 Table 2-7- Averages and standard deviations of TRC Arrival friction measurements using 501 tire ........ 13 Table 2-8- Coefficient of variation of TRC Arrival friction measurements using 501 tire ........................ 13 Table 2-9- Statistics of TRC Departure friction measurements for 501 tire ............................................... 17 Table 2-10- Coefficient of variation of TRC Departure friction measurements for 501 tire types ............ 17 Table 2-11- Statistics of TRC Departure friction measurements for 524 tire types.................................... 21 Table 2-12- Coefficient of variations of TRC Departure friction measurements using 524 tire ................ 21 Table 2-13- Pooled repeatability and reproducibility standard deviations of 501 tire Arrival and Departure friction data .............................................................................................................. 25 Table 2-14- Computed F- and critical F- values for comparison of precision estimates of 501 and 524 tires for different speeds .................................................................................................... 26 Table 2-15- Computed F- and critical F- values for comparison of precision estimates of 501 and 524 tires for different surfaces .................................................................................................. 26 Table 2-16- Pooled repeatability and reproducibility standard deviations of 501 and 524 tires ................. 26 Table 2-17- Computed F- and critical F- values for comparison of precision estimates of different speeds ........................................................................................................................................ 27 Table 2-18- Combined standard deviations of the 3 speeds for TRC surfaces ........................................... 27 Table 2-19- Computed F- and critical F- values for comparison of precision estimates of different TRC surfaces ..................................................................................................................................... 28 Table 2-20- Combined repeatability and reproducibility precisions for frictional properties of TRC measurements ........................................................................................................................... 28 Table 2-21- Computed F- and critical F- values for comparison of variances of TTI and TRC friction measurements ........................................................................................................................... 29 Table 2-22- Repeatability and reproducibility precisions for frictional measurements of various pavement surfaces ..................................................................................................................... 29

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 vi LIST OF FIGURES Figure 2-1- Box plots and h and k statistics for friction numbers of TTI Initial State System at 40 mph .... 9 Figure 2-2- Box plots and h and k statistics for friction numbers of TTI Final State System at 30 mph ... 10 Figure 2-3- Box plots and h and k statistics for friction numbers of TTI Final State System at 40 mph ... 11 Figure 2-4- Box plots and h and k statistics for friction numbers of TTI Final State System at 50 mph ... 12 Figure 2-5- Box plots and h and k statistics for friction numbers of TRC Arrival State System at 20 mph ...................................................................................................................................... 14 Figure 2-6- Box plots and h and k statistics for friction numbers of TRC Arrival State System at 40 mph ...................................................................................................................................... 15 Figure 2-7- Box plots and h and k statistics for friction numbers of TRC Arrival State System at 60 mph ...................................................................................................................................... 16 Figure 2-8- Box plots and h and k statistics for friction numbers of TRC Departure State System with 501 tire at 20 mph ..................................................................................................................... 18 Figure 2-9- Box plots and h and k statistics for friction numbers of TRC Departure State System with 501 tire at 40 mph ..................................................................................................................... 19 Figure 2-10- Box plots and h and k statistics for friction numbers of TRC Departure State Systems with 501 tires at 60 mph ........................................................................................................... 20 Figure 2-11- Box plots and h and k statistics for friction numbers of TRC Departure State Systems with 524 tires at 20 mph ........................................................................................................... 22 Figure 2-12- Box plots and h and k statistics for friction numbers of TRC Departure State Systems with 524 tires at 40 mph ........................................................................................................... 23 Figure 2-13- Box plots and h and k statistics for friction numbers of TRC Departure State Systems with 524 tires at 60 mph ........................................................................................................... 24

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 vii ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 9-26A by the AASHTO Materials Reference Laboratory (AMRL). Dr. Haleh Azari and Mr. Robert Lutz were co- principal investigators on the study. Mr. Peter Spellerberg, the former AMRL Manager, played an important supporting role. The authors wish to give special thanks to Mr. Dick Zimmer at the Texas Transportation Institute and Mr. Bill Lyon at the Transportation Research Center who provided the friction data used in this study.

NCHRP Web-Only Document 142: Precision Estimates of AASHTO T 242 viii ABSTRACT This report presents results of the study to prepare precision estimates for AASHTO T 242, “Frictional Properties of Paved Surfaces Using a Full-Scale Tire.” The data used in this study were provided by Texas Transportation Institute (TTI) and Transportation Research Center (TRC) from evaluation of state friction measurement systems that have been calibrated at their field test centers. Two sets of data were analyzed from each test center: “Initial” or “Arrival” and “Final” or “Departure“. The Initial set was collected by state systems as they arrived to each center for calibration. The Final set was collected after adjustments were made to the state systems to put them into compliance with AASHTO T 242. The variability of the friction measurements were examined for both Initial and Final systems to evaluate the effect of calibration on variability of the measurements. Only the Final State System data were used to determine the precision estimates for measuring frictional properties of paved surfaces. A draft precision statement for AASHTO T 242 is proposed and included in this report.

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TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 142: Precision Estimates of AASHTO T 242 examines precision estimates for AASHTO (American Association of State Highway and Transportation Officials) T 242, “Frictional Properties of Paved Surfaces Using a Full-Scale Tire.”

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