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ii Table of Contents Author Acknowledgments ................................................................................................................... 1 Executive Summary.............................................................................................................................. 2 Background and Objectives ............................................................................................................ 2 Study Methodology .......................................................................................................................... 2 Discussion of Results ........................................................................................................................ 3 In conclusion..................................................................................................................................... 4 1. Chapter 1 Introduction ............................................................................................................... 5 2. Chapter 2 Literature Review ...................................................................................................... 7 2.1. Pavement Marking and Marker Materials....................................................................... 8 2.1.1. Waterborne Paints........................................................................................................ 9 2.1.2. Conventional Solvent Paints ...................................................................................... 10 2.1.3. Thermoplastic............................................................................................................. 10 2.1.4. Tape............................................................................................................................ 11 2.1.5. Epoxy.......................................................................................................................... 11 2.1.6. Methyl Methacrylate................................................................................................... 12 2.1.7. Polyester..................................................................................................................... 13 2.1.8. Polyurea ..................................................................................................................... 13 2.2. Visibility and Retroreflectivity......................................................................................... 13 2.2.1. Contrast ...................................................................................................................... 16 2.2.2. Effect of the Color of Pavement Markings on Contrast and Retroreflectivity ........... 17 2.2.3. NTPEP Testing Facility Data..................................................................................... 18 2.2.4. Retroreflectivity Performance Testing ....................................................................... 26 2.2.5. Retroreflectivity Modeling.......................................................................................... 28 2.2.6. Retroreflectivity Performance Requirements ............................................................. 31 2.2.7. The Effects of Weather on the Performance of Pavement Markings.......................... 40 2.2.8. Snow-Removal Policy................................................................................................. 42 2.2.9. Pavement Surface Influence on Pavement Marking and Marker Visibility ............... 45 2.2.10. Summary of Visibility and Retroreflectivity ............................................................... 46 2.3. Human Factors.................................................................................................................. 46 2.3.1. Driver Behavior on Curves ........................................................................................ 47 2.3.2. Edgelines and Speed................................................................................................... 48 2.4. Safety Impact..................................................................................................................... 49 2.4.1. Driver Response, Delineation and Safety Effects....................................................... 60 2.4.2. Climatological Information and Wet Pavement ......................................................... 64 2.5. State of Art in Materials Research and Development ................................................... 66 2.5.1. Profiled Pavement Markings...................................................................................... 66 2.5.2. Contrast Pavement Markings ..................................................................................... 67
iii 2.6. Survey of Relevant Practices............................................................................................ 68 2.6.1. Installation/Application Policies and Procedures...................................................... 68 2.6.2. Pavement Marking and Marker Management Systems .............................................. 70 2.6.3. Performance Measures for Reapplication.................................................................. 71 2.6.4. Performance Evaluation............................................................................................. 73 2.7. Summary of the Relevant Findings from the Literature Review ................................. 79 3. Chapter 3 Study Methodology.................................................................................................. 82 3.1. Vision of the Research Study ........................................................................................... 82 3.2. Methodology Outline ........................................................................................................ 84 3.3. Study Enhanced Methodology ......................................................................................... 86 3.3.1. Focus on the Relationship Between Visibility and Safety........................................... 86 3.3.2. Focus upon Materials in Common Use ...................................................................... 86 3.3.3. Focus on Safety Over Time ........................................................................................ 87 3.4. Methodology for Modeling Retroreflectivity.................................................................. 87 3.5. Methodology for Examining the Relationship Between Safety and Retroreflectivity 88 3.6. Homogeneous Segments ................................................................................................... 94 3.7. Data Requirements - Simulation...................................................................................... 96 4. Chapter 4 Data Collection and Preparation.......................................................................... 100 4.1. Data Collection ................................................................................................................ 100 4.1.1. Retroreflectivity ........................................................................................................ 100 4.1.2. Pavement Marking and Marker Installation ............................................................ 101 4.1.3. Capital Pavement Projects ....................................................................................... 103 4.1.4. Roadway Inventory, Traffic Volume, and Crash Variables...................................... 103 4.1.5. Climate Region ......................................................................................................... 104 4.1.6. Historical Snowfall................................................................................................... 105 4.2. Data Preparation............................................................................................................. 106 4.2.1. Quality Control......................................................................................................... 106 4.2.2. Retroreflectivity Data Building ................................................................................ 107 4.2.3. Database Linking ..................................................................................................... 111 4.2.4. Database Manipulation............................................................................................ 112 4.3. Summary of the Retroreflectivity-Safety Database ..................................................... 116 5. Chapter 5 Retroreflectivity Modeling and Safety Analysis ................................................. 117 5.1. Retroreflectivity Modeling ............................................................................................. 117 5.1.1. Retroreflectivity Prediction Modeling of Pavement Markings................................. 117 5.1.2. Retroreflectivity Modeling of Pavement Markers .................................................... 135 5.1.3. Retroreflectivity Prediction Beyond 25 Months ....................................................... 141 5.1.4. Example Calculation of Retroreflectivity ................................................................. 148 5.1.5. Retroreflectivity Modeling Summary........................................................................ 150 5.2. Retroreflectivity-Safety Data Summary ....................................................................... 151
iv 5.3. Safety Analysis................................................................................................................. 154 5.3.1. Retroreflectivity Bin Ranges..................................................................................... 155 5.3.2. Safety Effect by Crash Severity................................................................................. 157 5.3.3. Safety Effect on Total Non-daylight, Non-intersection Crashes............................... 158 5.3.4. Effect of the First Full Month of New Stripping....................................................... 165 5.3.5. Sensitivity Analysis ................................................................................................... 167 6. Chapter 6 Discussion of Study Results................................................................................... 170 6.1. How do We Know the Methodology is Correct?.......................................................... 171 6.2. What if the Retroreflectivity Models are Inaccurate?................................................. 172 6.3. How Small Might the Safety Effect of Pavement Markings be?................................. 172 6.4. Limitations of the Study ................................................................................................. 173 7. Chapter 7 Conclusions and Recommendations..................................................................... 174 7.1. Recommended Future Research.................................................................................... 175 References ......................................................................................................................................... 177 Appendix A. Retroreflectivity Look-up Tables for Markings and Markers ........................... 187
v List of Figures Figure 1. Non-linear relationship between retroreflectivity and participant ratings, from Parker and Meja (17)...................................................................................................................................... 15 Figure 2. Non-linear relationship between retroreflectivity and participant ratings, from Loetterle, Beck and Carlson (16) ................................................................................................................. 16 Figure 3. Screenshot from the NTPEP website (23). ........................................................................... 19 Figure 4. Typical set-up for field tests using test decks. (24)............................................................... 20 Figure 5. ASTM D713 field test for pavement marking material (24)................................................. 21 Figure 6. Retroreflectivity measurements on the left wheel path and centerline(25)........................... 22 Figure 7. Four waterborne pavement markings retroreflectivity skip readings on asphalt for a 12 month period, from NTPEP (23). ................................................................................................ 23 Figure 8. Four waterborne pavement markings retroreflectivity skip readings on concrete for a 12 month period from NTPEP (23). ................................................................................................. 24 Figure 9. Left-wheel retroreflectivity pavement markings readings of the four markings in Figure 8, from NTPEP (23)......................................................................................................................... 25 Figure 10. Entrance and observation angles for 30-meter geometry, from the Highway Innovative Technology Center (26) ............................................................................................................... 27 Figure 11. Retroreflectivity degradation pattern of new (A), established (B), pavement markings, and degradation due to snowplowing (C), from Thamizharasan et al. (14) ....................................... 30 Figure 12. Mean curve recognition distances, from Molino et al. (34). ............................................... 35 Figure 13. Mean curve recognition distances from Molino et al. (36). ................................................ 37 Figure 14. Depiction of optic flow, for a straight segment and a curve, from Mestre (37).................. 37 Figure 15. Mean curve recognition distance for edgeline tradeoffs from Molino et al. (35). .............. 40 Figure 16. Detection distance versus retroreflectivity of marking, from Aktan and Schnell (39) ....... 41 Figure 17. 90-degree curve showing the trajectory drivers actually drive. .......................................... 48 Figure 18. Retroreflectivity requirements by vehicle speed, from Zwahlen and Schnell (55)............. 49 Figure 19. Screenshot of National Climatic Data Center (http://www.ncdc.noaa.gov/oa/ncdc.html).. 65 Figure 20. Full range of experimental conditions................................................................................. 85 Figure 21. Excerpt of capital pavement projects listing in California ................................................ 103 Figure 22. Marking age versus retroreflectivity (Source: NTPEP data)............................................. 118 Figure 23. Average marking age versus retroreflectivity (Source: NTPEP data) .............................. 119 Figure 24. Marking age versus average retroreflectivity by color (Source: NTPEP data) ................. 120 Figure 25. Observed and predicted average retroreflectivity for white and yellow waterborne and corresponding CURE plots (Source: NTPEP data).................................................................... 122 Figure 26. Observed and predicted average retroreflectivity for white and yellow epoxy and corresponding CURE plots (Source: NTPEP data).................................................................... 123 Figure 27. Observed and predicted average retroreflectivity for white and yellow thermoplastic and corresponding CURE plots (Source: NTPEP data).................................................................... 123 Figure 28. Observed and predicted average retroreflectivity for white and yellow methyl methacrylate and corresponding CURE plots (Source: NTPEP data)............................................................. 124
vi Figure 29. Observed and predicted average retroreflectivity for white and yellow permanent tape and corresponding CURE plots (Source: NTPEP data).................................................................... 124 Figure 30. Observed and predicted average retroreflectivity for white and yellow solvent and corresponding CURE plots (Source: NTPEP data).................................................................... 125 Figure 31. Distribution of AADT for white and yellow epoxy and solvent (Source: NTPEP data) .. 127 Figure 32. Distribution of AADT for white and yellow waterborne and thermoplastic (Source: NTPEP data) .............................................................................................................................. 128 Figure 33. Marking age by pavement surface for white and yellow waterborne and thermoplastic (Source: NTPEP data)................................................................................................................ 129 Figure 34. Marking age versus average retroreflectivity by white and yellow thermoplastic mixed humid and corresponding CURE plots (Source: NTPEP data).................................................. 131 Figure 35. Marking age versus average retroreflectivity for white and yellow waterborne mixed humid and corresponding CURE plots (Source: NTPEP data).................................................. 131 Figure 36. Marking age versus average retroreflectivity for white and yellow thermoplastic hot dry and corresponding CURE plots (Source: NTPEP data)............................................................. 132 Figure 37. Pavement marking age for white and yellow waterborne by heavy snow removal (Source: NTPEP data) .............................................................................................................................. 133 Figure 38. Pavement marking age for white and yellow thermoplastic by heavy snow removal (Source: NTPEP data)................................................................................................................ 134 Figure 39. Pavement marking age for white and yellow waterborne by low to medium snow removal (Source: NTPEP data)................................................................................................................ 134 Figure 40. Pavement marking age for white and yellow thermoplastic by low to medium snow removal (Source: NTPEP data).................................................................................................. 135 Figure 41. Marker age versus retroreflectivity (Source: NTPEP data)............................................... 136 Figure 42. Distribution of marker type (Source: NTPEP data) .......................................................... 137 Figure 43. Observed and predicted average retroreflectivity for plowable and non-plowable markers and corresponding CURE plots (Source: NTPEP data)............................................................. 138 Figure 44. Distribution of pavement surface (Source: NTPEP data) ................................................. 139 Figure 45. Distribution of snow removal (Source: NTPEP data) ....................................................... 140 Figure 46. Distribution of AADT (Source: NTPEP data) .................................................................. 141 Figure 47. Predicted average retroreflectivity for epoxy, methyl methacrylate, permanent tape and solvent........................................................................................................................................ 143 Figure 48. Predicted average retroreflectivity for thermoplastic by climate region........................... 144 Figure 49. Predicted average retroreflectivity for waterborne for mixed humid climate region........ 144 Figure 50. Predicted average retroreflectivity for white and yellow thermoplastic under heavy and low to medium snow removal........................................................................................................... 145 Figure 51. Predicted average retroreflectivity for waterborne by snow removal ............................... 146 Figure 52. Predicted average retroreflectivity for plowable and non-plowable markers ................... 147 Figure 53. Predicted average retroreflectivity for white waterborne heavy snow removal................ 149 Figure 54. Predicted average retroreflectivity for plowable markers ................................................. 150 Figure 55. Change in safety with change in number of crashes for multilane highways ................... 169
vii List of Tables Table 1. Degree of use of pavement marking materials by type, from Migletz and Graham (8)........... 8 Table 2. Degree of usage of retroreflectometers, from Migletz and Graham (8) ................................. 27 Table 3. Degree of usage of various subjective evaluations, from Migletz and Graham (8) ............... 28 Table 4. Experimental design used by Molino et al. (34)..................................................................... 34 Table 5. Experimental design used by Molino et al. (36)..................................................................... 36 Table 6. Experimental design used by Molino et al. (35)..................................................................... 39 Table 7. Minimum required retroreflectivity levels (RL), from Aktan and Schnell (39)..................... 42 Table 8. Minnesota snow and ice removal performance targets (43)................................................... 43 Table 9. Summary of Potters Industries (58) findings of the safety effect of MUTCD marking guidelines for edgelines and centerlines, ..................................................................................... 51 Table 10. Estimated service life by roadway type, pavement marking material, and color for sites without roadway lighting and permanent raised pavement markers, from Migletz et al. (2) ...... 59 Table 11. Experimental design used by Johnston (54). ........................................................................ 63 Table 12. WETTIME model from Harwood et al. (64)........................................................................ 66 Table 13. PRPM guidelines based on traffic volume for Illinois, Indiana, and Kansas ....................... 70 Table 14. PRPM replacement cycle for Indiana, from Bahar et al. (75) .............................................. 73 Table 15. PRPM system maintenance schedule for Texas, nighttime inspections from Bahar et al. (75) ..................................................................................................................................................... 73 Table 16. Suggested replacement cycles for raised pavement markers for Texas from Bahar et al. (75) ..................................................................................................................................................... 73 Table 17. Summary of objective and subjective evaluations of pavement markings........................... 75 Table 18. Minimum pavement marking retroreflectivity specifications .............................................. 76 Table 19. Minimum in-service retroreflectivity guidelines for pavement marking materials recommended by the FHWA (mcd/m2/lux) ................................................................................. 78 Table 20. Minimum in-service retroreflectivity guidelines for pavement marking materials recommended by state, county, and city agencies (mcd/m2/lux) ................................................. 79 Table 21. Example retroreflectivity bin ranges and numbers............................................................... 90 Table 22. Illustration of retroreflectivity table for analysis (months of remarking in bold)................. 91 Table 23. Illustration of retroreflectivity bins ...................................................................................... 93 Table 24. Variables: road identification ............................................................................................... 94 Table 25. Variables: pavement material type ....................................................................................... 95 Table 26. Variables: traffic volume...................................................................................................... 95 Table 27. Variables: marker installation dates ..................................................................................... 95 Table 28. Variables marking restriping dates ....................................................................................... 96 Table 29. Number of total target crashes required by road type .......................................................... 97 Table 30. HSIS volume and crash information for six states, and the values used in the simulation .. 98 Table 31. Number years and miles of road per year required by road type.......................................... 99 Table 32: Data sources and status ...................................................................................................... 100
viii Table 33. Excerpt of Californiaâs statewide MMS database, the older management system............. 102 Table 34. Roadway inventory, traffic volume, and crash variables ................................................... 104 Table 35. California climate regions .................................................................................................. 105 Table 36. NTPEP retroreflectivity database structure ........................................................................ 108 Table 37: Table 11 from NTPEP Report 98 (98) showing an outlier................................................. 109 Table 38. Marker retroreflectivity database structure ........................................................................ 110 Table 39. The look-up table used for linking counties in the retroreflectivity-safety database.......... 111 Table 40. Marker age based upon installation date ............................................................................ 113 Table 41. Detailed illustration of 12 marker age columns.................................................................. 113 Table 42. Detailed illustration of 12 marker luminance columns ...................................................... 114 Table 43. Retroreflectivity-safety database format and column headings.......................................... 115 Table 44. Total number of NTPEP observations by material type..................................................... 120 Table 45. Summary of model parameters by color and material type for all climate regions and snow removal ...................................................................................................................................... 121 Table 46. Number of observations by AADT for markings in NTPEP data ...................................... 126 Table 47. Number of NTPEP observations by climate region and material type............................... 130 Table 48. Summary of revised model parameters for color, material, climate region and age models ................................................................................................................................................... 130 Table 49. Categories for snow removal.............................................................................................. 132 Table 50. Summary of revised parameters for white and yellow waterborne and thermoplastic by snow removal effect................................................................................................................... 133 Table 51. Summary of model parameters by type.............................................................................. 138 Table 52. Categories for snow removal.............................................................................................. 139 Table 53. Number of observations by AADT for markers in NTPEP data ........................................ 141 Table 54. Parameter estimates for color, material type and age models ............................................ 147 Table 55. Parameter estimates for color, material type, age, and climate region models .................. 148 Table 56. Parameter estimates for color, material type, age, and snow removal models ................... 148 Table 57. Parameter estimates for type and age models..................................................................... 148 Table 58. California Manual on Uniform Traffic Control Devices marking summary...................... 152 Table 59. Illustration of age entries by month for one segment. ........................................................ 152 Table 60. Illustration of three segments resulting in an average of 5.75 miles of data per year ........ 153 Table 61. Total average miles per year of road by road type ............................................................. 153 Table 62. Total number of non-daylight, non-intersection crashes by road type ............................... 154 Table 63. Retroreflectivity bins apportioned by crashes and by miles for white markings ............... 156 Table 64. Retroreflectivity bins apportioned by crashes and by miles for yellow markings ............. 156 Table 65. Estimation results of safety effects qr for white markings by non-daylight, non-intersection crash severity ............................................................................................................................. 157 Table 66. Estimation pm results of seasonal effect for white markings by non-daylight, non- intersection crash severity.......................................................................................................... 157
ix Table 67. Safety estimation results for yellow markings by non-daylight, non-intersection crash severity....................................................................................................................................... 158 Table 68. Estimation pm results of seasonal effect for yellow markings by non-daylight, non- intersection crash severity.......................................................................................................... 158 Table 69. Estimation results of safety effects qr for white markings by total non-daylight, non- intersection crashes .................................................................................................................... 159 Table 70. Estimation pm results of seasonal effect for white markings by total non-daylight, non- intersection crashes .................................................................................................................... 160 Table 71. Estimation results of safety effects qr for yellow markings by total non-daylight, non- intersection crashes .................................................................................................................... 160 Table 72. Estimation results pm of seasonal effect for yellow markings by total non-daylight, non- intersection crashes .................................................................................................................... 160 Table 73. Estimation results of safety effects qr for markers by total non-daylight, non-intersection crashes........................................................................................................................................ 162 Table 74. Estimation results pm of seasonal effect for markers by total non-daylight, non-intersection crashes........................................................................................................................................ 162 Table 75. Safety effect estimation results for white and yellow markings combined for multilane freeways for all non-daylight, non-intersection crashes ............................................................ 163 Table 76. Safety effect estimation results for white and yellow markings combined for multilane highways for non-daylight, non-intersection crashes ................................................................ 164 Table 77. Safety effect estimation results for white and yellow markings combined for 2-lane highways for non-daylight, non-intersection crashes with standard error estimates ................. 165 Table 78. Estimation results of seasonal effect for white and yellow markings combined................ 165 Table 79. Retroreflectivity of relevant marking materials on first full month after striping (Age = 1) ................................................................................................................................................... 166 Table 80. Safety effect estimation results for white markings separating the effect of first full month of new stripping for all non-daylight, non-intersection crashes................................................. 166 Table 81. Estimation results pm of seasonal effect for white markings separating the effect of first full month of new stripping for all non-daylight, non-intersection crashes ..................................... 166 Table 82. Estimation results for yellow markings separating the safety effect of first full month of new striping for all non-daylight, non-intersection crashes ....................................................... 167 Table 83. Estimation results pm of seasonal effect for yellow markings separating the effect of first full month of new stripping for non-daylight, non-intersection crashes.................................... 167 Table 84. Safety effect with artificially increased number of crashes on multilane freeways ........... 168 Table 85. New York State seasonal factors from Hauer et al. (92), and California non-daylight hours ................................................................................................................................................... 172 Table 86. Retroreflectivity look up tables for pavement markings .................................................... 187
