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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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Suggested Citation:"Contents." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
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v C O N T E N T S SUMMARY ......................................................................................................................................................... 1  APPLICATION OF CRASH MODIFICATION FACTORS FOR ACCESS MANAGEMENT .......................................................................... 1  Background .......................................................................................................................................................... 1  Objectives ............................................................................................................................................................. 1  Approach .............................................................................................................................................................. 1  Results .................................................................................................................................................................. 3  CHAPTER 1 ......................................................................................................................................................... 5  INTRODUCTION .............................................................................................................................................................. 5  Background .......................................................................................................................................................... 5  Overall Study Objective ........................................................................................................................................ 6  Overview of Approach .......................................................................................................................................... 7  Scope of Final Report ............................................................................................................................................ 8  Chapter 1 References ........................................................................................................................................... 8  CHAPTER 2 ......................................................................................................................................................... 9  LITERATURE REVIEW ....................................................................................................................................................... 9  Introduction .......................................................................................................................................................... 9  Alternative Intersection and Interchange Design ............................................................................................... 11  Control Driveway Design Elements .................................................................................................................... 13  Convert Two‐Way Streets to One‐Way Operation ............................................................................................. 15  Establish Corner Clearance Criteria .................................................................................................................... 16  Improve Cross‐Connectivity ................................................................................................................................ 19  Install Non‐Traversable Medians, and Accommodate Left‐Turns and U‐Turns ................................................. 19  Install TWLTL on Undivided Highway ................................................................................................................. 24  Install Service or Frontage Roads ....................................................................................................................... 26  Install Traversable Medians ............................................................................................................................... 27  Left‐Turn Treatment ........................................................................................................................................... 28  Manage Location and Spacing of Unsignalized Access ...................................................................................... 29  Manage Spacing of Traffic Signals ..................................................................................................................... 32  Manage the Location, Spacing, and Design of Median Openings and Crossovers ............................................. 35  Manage the Spacing of Signalized and Unsignalized Access on Crossroads in the Vicinity of Freeway  Interchanges ....................................................................................................................................................... 36  Provide Adequate Sight Distance at Access Points ............................................................................................. 38  Right‐Turn Treatment......................................................................................................................................... 39  Summary ............................................................................................................................................................ 40  Chapter 2 References ......................................................................................................................................... 44  CHAPTER 3 ........................................................................................................................................................ 47  DATA RECONNAISSANCE AND ASSESSMENT ....................................................................................................................... 47  Introduction ........................................................................................................................................................ 47  Survey ................................................................................................................................................................. 47  Data Reconnaissance ......................................................................................................................................... 58 

vi CHAPTER 4 ........................................................................................................................................................ 66  GAP ANALYSIS ............................................................................................................................................................. 66  Introduction ........................................................................................................................................................ 66  Summary of Gap Analysis and Possible Data Sources ........................................................................................ 66  Prioritization of NCHRP 17‐74 Research ............................................................................................................. 70  CHAPTER 5 ........................................................................................................................................................ 78  STUDY DESIGN ............................................................................................................................................................ 78  Introduction ........................................................................................................................................................ 78  Methodology ...................................................................................................................................................... 79  Chapter 5 References ......................................................................................................................................... 83  CHAPTER 6 ........................................................................................................................................................ 84  DATA COLLECTION ....................................................................................................................................................... 84  Introduction ........................................................................................................................................................ 84  Existing Datasets Used ....................................................................................................................................... 84  Data Collection Process ...................................................................................................................................... 85  Summary Statistics ............................................................................................................................................. 90  CHAPTER 7 ........................................................................................................................................................ 97  ANALYSIS RESULTS ....................................................................................................................................................... 97  Introduction ........................................................................................................................................................ 97  Intersections ....................................................................................................................................................... 97  Segments .......................................................................................................................................................... 103  CHAPTER 8 ...................................................................................................................................................... 184  PRACTITIONER GUIDE ................................................................................................................................................. 184  Introduction ...................................................................................................................................................... 184  Objective of the Guide ...................................................................................................................................... 184  Benefits of Using the Guide .............................................................................................................................. 184  Chapter 1: Introduction .................................................................................................................................... 184  Chapter 2: Definitions for Quantitative Safety Analysis ................................................................................... 185  Chapter 3: Safety Effects of Access Management ............................................................................................ 185  Chapter 4: Segment‐ and Intersection‐Level Analysis ...................................................................................... 186  Chapter 5: Corridor‐Level Analysis ................................................................................................................... 186  Chapter 6: Communicating Results .................................................................................................................. 187  CHAPTER 9 ...................................................................................................................................................... 188  FOCUS GROUP .......................................................................................................................................................... 188  Introduction ...................................................................................................................................................... 188  Focus Group Meetings...................................................................................................................................... 189  Chapter 9 References ....................................................................................................................................... 191  CHAPTER 10 .................................................................................................................................................... 192  IMPLEMENTATION PLAN .............................................................................................................................................. 192  Dissemination ................................................................................................................................................... 192  Implementation ................................................................................................................................................ 193  Evaluation ........................................................................................................................................................ 195  CHAPTER 11 .................................................................................................................................................... 196  CONCLUSIONS ........................................................................................................................................................... 196 

vii ABBREVIATIONS, ACRONYMS, INITIALISMS, AND SYMBOLS ............................................................................. 199  APPENDIX A .................................................................................................................................................... A‐1  SURVEY QUESTIONS ................................................................................................................................................... A‐1  APPENDIX B .................................................................................................................................................... B‐1  COMMENTS ON SURVEY RESPONSES .............................................................................................................................. B‐1  APPENDIX C .................................................................................................................................................... C‐1  OVERVIEW OF GOODNESS‐OF‐FIT MEASURES ................................................................................................................. C‐1  Appendix C References ..................................................................................................................................... C‐7 

viii List of Figures Figure 1. Illustration of the differences in access management features ...................................................... 6  Figure 2. Intersection physical area. ........................................................................................................... 17  Figure 3. Intersection functional area. ........................................................................................................ 18  Figure 4. Improved access configuration with cross-connectivity. ............................................................. 19  Figure 5. Allowable traffic movements before and after raised median installation. (Gluck et al. 1999) .. 21  Figure 6. Potential frontage road configuration. ......................................................................................... 26  Figure 7. Illustration of unsignalized driveway spacing. ............................................................................ 30  Figure 8. Comparison of uniform and non-uniform signal spacing. (Gluck et al. 1999) ............................ 33  Figure 9. Example CMF for total crashes for changing traffic signal density. ........................................... 33  Figure 10. Example CMF for severe crashes for changing traffic signal density. ...................................... 33  Figure 11. Example CMF for total crashes for changing median opening density. .................................... 35  Figure 12. Example CMFs for ramp terminal spacing. ............................................................................... 37  Figure 13. Distribution and representation of survey respondents. ............................................................ 48  Figure 14. Question 1: Do you quantify the safety effects of access management strategies to support related decisions? ........................................................................................................................................ 49  Figure 15. Question 2: Do you have a policy or procedure for assessing the safety effects of access management strategies? .............................................................................................................................. 50  Figure 16. Question 3: Do you track safety-related performance measures after implementing access management strategies? .............................................................................................................................. 51  Figure 17. Question 4: What is your priority need to estimate the safety effects of access management strategies? .................................................................................................................................................... 52  Figure 18. Question 5: What are your priority needs in terms of the level of analysis? ............................. 53  Figure 19. Equation for computing calibration factor. ................................................................................ 81  Figure 20. Equation for applying calibration factor. ................................................................................... 81  Figure 21. Equation for variance of CMF. .................................................................................................. 82  Figure 22. Equation for modeling crashes. ................................................................................................. 82  Figure 23. Equation for modeling natural log of crashes. ........................................................................... 82  Figure 24. Screenshot of milepost markers in GIS. .................................................................................... 86  Figure 25. Screenshot of a milepost marker in Google Earth. .................................................................... 87  Figure 26. Screenshot of intersection location information from NCHRP 17-62. ...................................... 88  Figure 27. CURE plot 3ST and 4ST fitted values. ...................................................................................... 98  Figure 28. CURE plot 3ST and 4ST distance to ramp terminal. ................................................................. 99  Figure 29. CURE plot 3SG and 4SG fitted values. ..................................................................................... 99  Figure 30. CURE plot 3SG and 4SG distance to ramp terminal. .............................................................. 100  Figure 31. CURE plot Ohio 4D fitted values. ........................................................................................... 104  Figure 32. CURE plot Ohio 4D median opening density. ........................................................................ 104  Figure 33. CURE plot Minnesota 4D fitted values. .................................................................................. 105  Figure 34. CURE plot Minnesota 4D median opening density. ............................................................... 106  Figure 35. CURE plot Minnesota 4D maximum median opening spacing. .............................................. 108  Figure 36. CURE plot Minnesota 4D minimum median opening spacing. .............................................. 108  Figure 37. CURE plot Minnesota 4D number of full median openings. .................................................. 111  Figure 38. CURE plot Minnesota 4D number of one-directional median openings. ................................ 111  Figure 39. CURE plot Minnesota 4D number of two-directional median openings. ................................ 112 

ix Figure 40. CURE plot Minnesota 4D number full median openings with left-turn lane. ......................... 112  Figure 41. CURE plot Minnesota 4D number one directional median openings with left-turn lane. ....... 113  Figure 42. CURE plot Minnesota 4D number two directional median openings with left-turn lanes. ..... 113  Figure 43. CURE plot Ohio 2U minimum corner clearance. .................................................................... 119  Figure 44. CURE plot Ohio 2U maximum corner clearance. ................................................................... 119  Figure 45. CURE plot Ohio 2U average corner clearance. ....................................................................... 120  Figure 46. CURE plot Ohio 3T minimum corner clearance. .................................................................... 120  Figure 47. CURE plot Ohio 3T maximum corner clearance. ................................................................... 121  Figure 48. CURE plot Ohio 3T average corner clearance. ....................................................................... 121  Figure 49. CURE plot Ohio 4D minimum corner clearance. .................................................................... 122  Figure 50. CURE plot Ohio 4D maximum corner clearance. ................................................................... 122  Figure 51. CURE plot Ohio 4D average corner clearance. ....................................................................... 123  Figure 52. CURE plot Ohio 4U minimum corner clearance. .................................................................... 123  Figure 53. CURE plot Ohio 4U maximum corner clearance. ................................................................... 124  Figure 54. CURE plot Ohio 4U average corner clearance. ....................................................................... 124  Figure 55. CURE plot Ohio 5T minimum corner clearance. .................................................................... 125  Figure 56. CURE plot Ohio 5T maximum corner clearance. ................................................................... 125  Figure 57. CURE plot Ohio 5T average corner clearance. ....................................................................... 126  Figure 58. CURE plot Minnesota 2U minimum corner clearance. ........................................................... 127  Figure 59. CURE plot Minnesota 2U maximum corner clearance. .......................................................... 128  Figure 60. CURE plot Minnesota 2U average corner clearance. .............................................................. 128  Figure 61. CURE plot Minnesota 3T minimum corner clearance. ........................................................... 129  Figure 62. CURE plot Minnesota 3T maximum corner clearance. ........................................................... 129  Figure 63. CURE plot Minnesota 3T average corner clearance. .............................................................. 130  Figure 64. CURE plot Minnesota 4D minimum corner clearance. ........................................................... 130  Figure 65. CURE plot Minnesota 4D maximum corner clearance. .......................................................... 131  Figure 66. CURE plot Minnesota 4D average corner clearance. .............................................................. 131  Figure 67. CURE plot Minnesota 4U minimum corner clearance. ........................................................... 132  Figure 68. CURE plot Minnesota 4U maximum corner clearance. .......................................................... 132  Figure 69. CURE plot Minnesota 4U average corner clearance. .............................................................. 133  Figure 70. CURE plot Minnesota 5T minimum corner clearance. ........................................................... 133  Figure 71. CURE plot Minnesota 5T maximum corner clearance. ........................................................... 134  Figure 72. CURE plot Minnesota 5T average corner clearance. .............................................................. 134  Figure 73. CURE plot Ohio 2U number of signalized intersections. ........................................................ 139  Figure 74. CURE plot Ohio 2U signalized intersection density. .............................................................. 139  Figure 75. CURE plot Ohio 3T number of signalized intersections. ........................................................ 140  Figure 76. CURE plot Ohio 3T signalized intersection density. ............................................................... 140  Figure 77. CURE plot Ohio 4D number of signalized intersections. ........................................................ 141  Figure 78. CURE plot Ohio 4D signalized intersection density. .............................................................. 141  Figure 79. CURE plot Ohio 4U number of signalized intersections. ........................................................ 142  Figure 80. CURE plot Ohio 4U signalized intersection density. .............................................................. 142  Figure 81. CURE plot Ohio 5T number of signalized intersections. ........................................................ 143  Figure 82. CURE plot Ohio 5T signalized intersection density. ............................................................... 143  Figure 83. CURE plot Minnesota 2U fitted values. .................................................................................. 145  Figure 84. CURE plot Minnesota 2U signalized intersection density. ..................................................... 146  Figure 85. CURE plot Minnesota 3T fitted values. .................................................................................. 146  Figure 86. CURE plot Minnesota 3T signalized intersection density. ...................................................... 147  Figure 87. CURE plot Minnesota 4D fitted values. .................................................................................. 147  Figure 88. CURE plot Minnesota 4D signalized intersection density. ..................................................... 148  Figure 89. CURE plot Minnesota 4U fitted values. .................................................................................. 148  Figure 90. CURE plot Minnesota 4U signalized intersection density. ..................................................... 149 

x Figure 91. CURE plot Minnesota 5T fitted values. .................................................................................. 149  Figure 92. CURE plot Minnesota 5T signalized intersection density. ...................................................... 150  Figure 93. CURE plot Minnesota unsignalized intersections fitted values. .............................................. 152  Figure 94. CURE plot Minnesota unsignalized intersections maximum spacing. .................................... 152  Figure 95. CURE plot Minnesota unsignalized intersections minimum spacing. .................................... 153  Figure 96. CURE plot Ohio 2U number of unsignalized intersections. .................................................... 155  Figure 97. CURE plot Ohio 2U unsignalized intersection density. .......................................................... 156  Figure 98. CURE plot Ohio 3T number of unsignalized intersections. .................................................... 156  Figure 99. CURE plot Ohio 3T unsignalized intersection density. ........................................................... 157  Figure 100. CURE plot Ohio 4D number of unsignalized intersections. .................................................. 157  Figure 101. CURE plot Ohio 4D unsignalized intersection density. ........................................................ 158  Figure 102. CURE plot Ohio 4U number of unsignalized intersections. .................................................. 158  Figure 103. CURE plot Ohio 4U unsignalized intersection density. ........................................................ 159  Figure 104. CURE plot Ohio 5T number of unsignalized intersections. .................................................. 159  Figure 105. CURE plot Ohio 5T unsignalized intersection density. ......................................................... 160  Figure 106. CURE plot Minnesota 2U number of unsignalized intersections. ......................................... 162  Figure 107. CURE plot Minnesota 2U unsignalized intersection density. ............................................... 162  Figure 108. CURE plot Minnesota 3T number of unsignalized intersections. ......................................... 163  Figure 109. CURE plot Minnesota 3T unsignalized intersection density. ................................................ 163  Figure 110. CURE plot Minnesota 4D number of unsignalized intersections. ......................................... 164  Figure 111. CURE plot Minnesota 4D unsignalized intersection density. ............................................... 164  Figure 112. CURE plot Minnesota 4U number of unsignalized intersections. ......................................... 165  Figure 113. CURE plot Minnesota 4U unsignalized intersection density. ............................................... 165  Figure 114. CURE plot Minnesota 5T number of unsignalized intersections. ......................................... 166  Figure 115. CURE plot Minnesota 5T unsignalized intersection density. ................................................ 166  Figure 116. CURE plot Ohio 2U number of unsignalized access points. ................................................. 169  Figure 117. CURE plot Ohio 2U unsignalized access density. ................................................................. 169  Figure 118. CURE plot Ohio 3T number of unsignalized access points. ................................................. 170  Figure 119. CURE plot Ohio 3T unsignalized access density. ................................................................. 170  Figure 120. CURE plot Ohio 4D number of unsignalized access points. ................................................. 171  Figure 121. CURE plot Ohio 4D unsignalized access density. ................................................................. 171  Figure 122. CURE plot Ohio 4U number of unsignalized access points. ................................................. 172  Figure 123. CURE plot Ohio 4U unsignalized access density. ................................................................. 172  Figure 124. CURE plot Ohio 5T number of unsignalized access points. ................................................. 173  Figure 125. CURE plot Ohio 5T unsignalized access density. ................................................................. 173  Figure 126. CURE plot Minnesota 2U fitted values. ................................................................................ 175  Figure 127. CURE plot Minnesota 2U unsignalized access points........................................................... 176  Figure 128. CURE plot Minnesota 2U unsignalized access density. ........................................................ 176  Figure 129. CURE plot Minnesota 3T fitted values. ................................................................................ 177  Figure 130. CURE plot Minnesota 3T unsignalized access points. .......................................................... 177  Figure 131. CURE plot Minnesota 3T unsignalized access density. ........................................................ 178  Figure 132. CURE plot Minnesota 4D fitted values. ................................................................................ 178  Figure 133. CURE plot Minnesota 4D unsignalized access points........................................................... 179  Figure 134. CURE plot Minnesota 4D unsignalized access density. ........................................................ 179  Figure 135. CURE plot Minnesota 4U fitted values. ................................................................................ 180  Figure 136. CURE plot Minnesota 4U unsignalized access points........................................................... 180  Figure 137. CURE plot Minnesota 4U unsignalized access density. ........................................................ 181  Figure 138. CURE plot Minnesota 5T fitted values. ................................................................................ 181  Figure 139. CURE plot Minnesota 5T unsignalized access points. .......................................................... 182  Figure 140. CURE plot Minnesota 5T unsignalized access density. ........................................................ 182  Figure C-1. Mean absolute deviation. ....................................................................................................... C-1 

xi Figure C-2. Modified R2 value. ................................................................................................................ C-1  Figure C-3. Variance of negative binomial distribution. .......................................................................... C-2  Figure C-4. Dispersion parameter. ............................................................................................................ C-2  Figure C-5. Coefficient of variation of a constant calibration factor. ....................................................... C-2  Figure C-6. Variance of calibration factor. ............................................................................................... C-3  Figure C-7. Example CURE plot. ............................................................................................................. C-4  Figure C-8. Akaike’s Information Criterion (AIC). .................................................................................. C-5  Figure C-9. Schwarz Bayesian Information Criterion (BIC). ................................................................... C-5 

xii List of Tables Table 1. Summary of research plan. ............................................................................................................. 7  Table 2. Access management strategies, substrategies, and principles. ........................................................ 9  Table 3. Summary of intersection level CMFs for alternative intersection and interchange design. ......... 12  Table 4. Summary of SPFs related to alternative intersection designs. ...................................................... 13  Table 5. Summary of intersection level CMFs for control driveway design elements. .............................. 14  Table 6. Summary of site level CMFs for control driveway design elements. ........................................... 15  Table 7. Summary of SPFs related to driveway design elements. .............................................................. 15  Table 8. Summary of site level CMFs for two-way to one-way conversion. ............................................. 16  Table 9. Summary of SPFs related to two-way to one-way conversion. .................................................... 16  Table 10. Summary of intersection level CMFs for establishing corner clearance criteria. ....................... 18  Table 11. Summary of intersection level CMFs for installing non-traversable medians and accommodating left-turns and U-turns. ...................................................................................................... 22  Table 12. Summary of site level CMFs for installing non-traversable medians and accommodating left- turns and U-turns. ........................................................................................................................................ 22  Table 13. Summary of corridor level CMFs for installing non-traversable medians and accommodating left-turns and U-turns. ................................................................................................................................. 22  Table 14. Summary of SPFs related to installing non-traversable medians and accommodating left-turns and U-turns.................................................................................................................................................. 23  Table 15. Summary of intersection level CMFs for installing TWLTL on undivided highway. ................ 25  Table 16. Summary of site level CMFs for installing TWLTL on undivided highway. ............................. 25  Table 17. Summary of corridor level CMFs for installing TWLTL on undivided highway. ..................... 25  Table 18. Summary of SPFs related to TWLTLs. ...................................................................................... 25  Table 19. Summary of site level CMFs for installation of service or frontage roads. ................................ 26  Table 20. Summary of corridor level CMFs for installation of service or frontage roads. ......................... 27  Table 21.Summary of intersection level CMFs for installing traversable medians. ................................... 27  Table 22. Summary of site level CMFs for installing traversable medians. ............................................... 28  Table 23. Summary of corridor level CMFs for installing traversable medians. ........................................ 28  Table 24. Summary of intersection level CMFs for left-turn treatment. ..................................................... 29  Table 25. Summary of site level CMFs for left-turn treatment. .................................................................. 29  Table 26. Summary of intersection level CMFs for managing location and spacing of unsignalized access. .................................................................................................................................................................... 31  Table 27. Summary of site level CMFs for managing location and spacing of unsignalized access. ......... 31  Table 28. Summary of corridor level CMFs for managing location and spacing of unsignalized access. . 31  Table 29. Summary of SPFs related to the location and spacing of unsignalized access points. ............... 32  Table 30. Summary of site level CMFs for managing spacing of traffic signals. ....................................... 34  Table 31. Summary of corridor level CMFs for managing spacing of traffic signals. ............................... 34  Table 32. Summary of SPFs related to the spacing of signalized intersections. ......................................... 34  Table 33. Summary of intersection level CMFs for managing the location, spacing, and design of median openings and crossovers. ............................................................................................................................ 35  Table 34. Summary of site level CMFs for managing the location, spacing, and design of median openings and crossovers. ............................................................................................................................ 36  Table 35. Summary of corridor level CMFs for managing the location, spacing, and design of median openings and crossovers. ............................................................................................................................ 36 

xiii Table 36. Summary of SPFs related to the location, spacing, and design of median openings and crossovers. ................................................................................................................................................... 36  Table 37. Summary of site level CMFs for managing the spacing of signalized and unsignalized access on crossroads in the vicinity of freeway interchanges. .................................................................................... 37  Table 38. Summary of SPFs related to the spacing of signalized and unsignalized access on crossroads in the vicinity of freeway interchanges. .......................................................................................................... 38  Table 39. Summary of intersection level CMFs for providing adequate sight distance at access points. .. 39  Table 40. Summary of intersection level CMFs for right-turn treatment. .................................................. 40  Table 41. Summary of site level CMFs for right-turn treatment. ............................................................... 40  Table 42. Summary of available and high-quality CMFs for each category and subcategory. .................. 41  Table 43. Summary of available SPFs for each category and subcategory. ............................................... 43  Table 44. Survey summary: level of analysis. ............................................................................................ 53  Table 45. Survey summary: priority access management strategies. .......................................................... 54  Table 46. Survey summary: contacts. ......................................................................................................... 56  Table 47. Survey summary: additional contacts. ........................................................................................ 57  Table 48. Summary of data reconnaissance findings. ................................................................................. 60  Table 49. Gaps identified as high priority. .................................................................................................. 67  Table 50. Gaps NOT identified as high priority. ........................................................................................ 69  Table 51. Summary of access management strategies in Highway Safety Manual (1st Edition) ( indicates a CMF is available, -- indicates no CMF is available). ............................................................... 71  Table 52. CMFs for providing median based on Highway Safety Manual (1st Edition) Part C Predictive Method for urban four-lane undivided (4U) and divided (4D) arterials. .................................................... 76  Table 53. Driveway density CMFs inferred from the Highway Safety Manual (1st Edition) Part C Predictive Method for multi-vehicle crashes on urban four-lane undivided (4U) and divided (4D) arterials. .................................................................................................................................................................... 76  Table 54. High-priority strategies. .............................................................................................................. 77  Table 55. Applicable crash prediction models from Highway Safety Manual (1st Edition) Chapter 12 (Urban/Suburban Arterials). ....................................................................................................................... 78  Table 56. Base conditions for NCHRP Project 17-62 SPFs. ...................................................................... 79  Table 57. Illustration of CMF estimation by calibration factors. ................................................................ 81  Table 58. Additional variables collected. .................................................................................................... 85  Table 59. Number of intersections and crash totals by intersection type (Ohio). ....................................... 91  Table 60: Number of intersections and crash totals by intersection type (North Carolina). ....................... 91  Table 61. Descriptive statistics by intersection type (Ohio). ...................................................................... 92  Table 62. Descriptive statistics by intersection type (North Carolina). ...................................................... 93  Table 63. Number of segments and crash totals by segment type (Ohio). .................................................. 94  Table 64. Number of segments and crash totals by segment type (Minnesota). ......................................... 94  Table 65. Descriptive statistics by segment type (Ohio). ............................................................................ 95  Table 66. Descriptive statistics by segment type (Minnesota). ................................................................... 96  Table 67. Ohio distance to ramp terminal CURE plot measures. ............................................................... 98  Table 68. Ohio distance to ramp terminal CMFs. ..................................................................................... 100  Table 69. Ohio distance to ramp terminal GLM results. ........................................................................... 101  Table 70. Ohio right-turn lane channelization CMFs. .............................................................................. 101  Table 71. Ohio right-turn lane channelization GLM results. .................................................................... 102  Table 72. North Carolina right-turn lane channelization CMFs. .............................................................. 102  Table 73. North Carolina right-turn lane channelization GLM Results. ................................................... 102  Table 74. Combined Ohio and North Carolina right-turn lane channelization GLM results. ................... 103  Table 75. Ohio median opening density goodness-of-fit measures. ......................................................... 103  Table 76. Ohio median opening density GLM results. ............................................................................. 103  Table 77. Minnesota median opening density goodness-of-fit measures. ................................................ 105  Table 78. Minnesota median opening density GLM results. .................................................................... 105 

xiv Table 79. Ohio median opening spacing goodness-of-fit measures. ........................................................ 107  Table 80. Ohio median opening spacing GLM results. ............................................................................ 107  Table 81. Ohio median openings by type goodness-of-fit measures. ....................................................... 109  Table 82. Ohio median openings by type GLM results - model form 1. .................................................. 110  Table 83. Ohio median openings by type GLM results - model form 2. .................................................. 110  Table 84. Minnesota median openings by type goodness-of-fit measures. .............................................. 114  Table 85. Minnesota median openings by type GLM results - model form 1. ......................................... 114  Table 86. Minnesota median openings by type GLM results - model form 2. ......................................... 115  Table 87. Minnesota median openings by type assessment table results. ................................................. 116  Table 88. Ohio corner clearance goodness-of-fit measures. ..................................................................... 117  Table 89. Ohio minimum corner clearance GLM results. ........................................................................ 118  Table 90. Ohio maximum corner clearance GLM results. ........................................................................ 118  Table 91. Ohio average corner clearance GLM results. ............................................................................ 118  Table 92. Minnesota corner clearance goodness-of-fit measures. ............................................................ 127  Table 93. Minnesota minimum corner clearance GLM results. ................................................................ 135  Table 94. Minnesota maximum corner clearance GLM results. ............................................................... 135  Table 95. Minnesota average corner clearance GLM results. ................................................................... 135  Table 96. Ohio minimum corner clearance by upstream/downstream corner GLM results. .................... 136  Table 97. Ohio maximum corner clearance by upstream/downstream corner GLM results. ................... 136  Table 98. Ohio average corner clearance by upstream/downstream corner GLM results. ....................... 137  Table 99. Ohio signalized intersection goodness-of-fit measures. ........................................................... 138  Table 100. Ohio signalized intersection density GLM results. ................................................................. 144  Table 101. Ohio signalized intersection count GLM results. .................................................................... 144  Table 102. Minnesota signalized intersections goodness-of-fit measures. ............................................... 145  Table 103. Minnesota signalized intersection density GLM results. ........................................................ 150  Table 104. Minnesota number of signalized intersections GLM results. .................................................. 150  Table 105. Minnesota unsignalized intersection spacing goodness-of-fit measures. ............................... 151  Table 106. Minnesota minimum unsignalized intersection spacing GLM results. ................................... 153  Table 107. Minnesota maximum unsignalized intersection spacing GLM results. .................................. 153  Table 108. Ohio unsignalized intersection goodness-of-fit measures....................................................... 155  Table 109. Ohio unsignalized intersection density GLM results. ............................................................. 160  Table 110. Ohio unsignalized intersection count GLM results. ................................................................ 160  Table 111. Minnesota unsignalized intersections goodness-of-fit measures. ........................................... 161  Table 112. Minnesota unsignalized intersection density GLM results. .................................................... 167  Table 113. Minnesota unsignalized intersection count GLM results. ....................................................... 167  Table 114. Ohio unsignalized access goodness-of-fit measures. .............................................................. 168  Table 115. Ohio unsignalized access density GLM results. ..................................................................... 174  Table 116. Ohio unsignalized access points GLM results. ....................................................................... 174  Table 117. Minnesota unsignalized access goodness-of-fit measures. ..................................................... 175  Table 118. Minnesota unsignalized access density GLM results.............................................................. 183  Table 119. Minnesota unsignalized access points GLM results. .............................................................. 183  Table 120. Focus group members (in addition to the 17-74 Panel). ........................................................ 188  Table B-1. Question 1- Do you quantify the safety effects of access management strategies to support related decisions? ...................................................................................................................................... B-1  Table B-2. Question 2- Do you have a policy or procedure for assessing the safety effects of access management strategies? ............................................................................................................................ B-2  Table B-3. Question 3- Do you track safety-related performance measures after implementing access management strategies? ............................................................................................................................ B-3  Table B-4. Question 4- What is your priority need to estimate the safety effects of access management strategies? (Please select your higher priority) ......................................................................................... B-3 

xv Table B-5. Question 7- Are there other access management strategies or combination(s) of strategies that should be prioritized in this project? ......................................................................................................... B-4  Table C-1. Example of categorical variable assessment. .......................................................................... C-6  Table C-2. Summary of goodness-of-fit measures for ranking SPFs. ...................................................... C-7 

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Application of Crash Modification Factors for Access Management, Volume 2: Research Overview Get This Book
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The 1st Edition, in 2010, of the AASHTO Highway Safety Manual revolutionized the transportation engineering practice by providing crash modification factors and functions, along with methods that use safety performance functions for estimating the number of crashes within a corridor, subsequent to implementing safety countermeasures.

The TRB National Cooperative Highway Research Program's pre-publication draft ofNCHRP Research Report 974: Application of Crash Modification Factors for Access Management, Volume 2: Research Overview documents the research process related to access management features.

Supplementary to the report is the pre-publication draft of NCHRP Research Report 974: Application of Crash Modification Factors for Access Management, Volume 1: Practitioner’s Guide and a summary presentation for the two volumes.

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