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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWAHRT14057 Date: February 2018 
Publication Number: FHWAHRT14057 Date: February 2018 
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Access management (AM) is the process that provides (or manages) access to land development while preserving safety, capacity, and speed on the surrounding road network. A growing number of agencies have included closing, consolidating, or improving driveways, median openings, and intersections as part of their AM implementation strategy. However, these same agencies are often challenged to provide rigorous justifications that explain the safety benefits of their policies, practices, and strategies.
The objective of this research was to develop crash prediction models for evaluating the safety effects of corridor AM policies and strategies on urban, suburban, and urbanizing arterials. Corridorlevel crash prediction models were developed using more than 600 mi of detailed corridor data from four different regions in the United States. Agencies can use the crash prediction models to assess the safety impacts of their decisions related to corridor AM.
Monique R. Evans, P.E., CPM
Director, Office of Safety, Research
and Development
Notice
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Technical Report Documentation Page
1. Report No.
FHWAHRT14057 
2. Government Accession No.

3 Recipient's Catalog No.


4. Title and Subtitle
Safety Evaluation of Access Management Policies and Techniques 
5. Report Date
February 2018 

6. Performing Organization Code


7. Author(s)
Frank Gross, Craig Lyon, Bhagwant Persaud, Jerome Gluck, Matt Lorenz, and Scott Himes 
8. Performing Organization Report No.


9. Performing Organization Name and Address
Vanasse Hangen Bustlin, Inc. (VHB) 
10. Work Unit No. (TRAIS)


11. Contract or Grant No.
DFTH6109C00026 

12. Sponsoring Agency Name and Address
Office of Safety Research and Development 
13. Type of Report and Period Covered
Final Report: October 2009October 2013 

14. Sponsoring Agency Code
HRDS10 

15. Supplementary Notes
The Contracting Officer’s Representative of this project is Dr. Wei Zhang (HRDS10). Technical panel members include Dr. Joe Bared and Neil Spiller. 

16. Abstract
Access management (AM) is the process that provides (or manages) access to land development while preserving safety, capacity, and speed on the surrounding road network. These benefits have been increasingly recognized at all levels of government, and a growing number of agencies are managing access by requiring driveway permit applications and establishing where new access should be allowed. They are also closing, consolidating, or improving driveways, median openings, and intersections as part of their AM implementation strategy. However, these decisions are often challenged for various reasons, and there have been few scientifically rigorous evaluations to quantify the safety effects of corridor AM. As such, there is a need to provide additional information to help rationalize decisions related to AM so that agencies can better explain the safety benefits of their policies and practices. This study seeks to fill some of the safetyrelated research gaps—namely, to quantify the safety impacts of corridor AM decisions.
The objective of this research was to evaluate the safety effects of corridor AM policies and strategies on urban, suburban, and urbanizing arterials. Crash prediction models were developed using more than 600 mi of detailed corridor data from four different regions in the United States. The crash prediction models were estimated using generalized linear modeling. Agencies can use the crash prediction models to assess the safety impacts of their decisions related to corridor AM. 

17. Key Words
Access management, safety analysis, crash prediction models 
18. Distribution Statement
No restrictions. This document is available to the public through NTIS: National Technical Information Service, Springfield, VA 22161. 

19. Security Classification (of this report) Unclassified 
20. Security Classification (of this page) Unclassified 
21. No. of Pages
176 
22. Price

Form DOT F 1700.7 (872)  Reproduction of completed page authorized 
SI* (Modern Metric) Conversion Factors
Figure 1. Illustration. Unsignalized driveway spacing.
Figure 2. Illustration. Comparison of uniform and nonuniform signal spacing (figure 5 in Gluck, Levinson, and Stover, 1999).^{(3)}
Figure 3. Illustration. Intersection physical area versus functional area (adapted from Transportation Research Circular 456, figure 4).^{(4)}
Figure 4. Illustration. Allowable traffic movements before and after raised median installation (figure 30 in Gluck, Levinson, and Stover, 1999).^{(3)}
Figure 5. Illustration. Potential frontage road configuration.
Figure 6. Illustration. Improved access configuration with cross connectivity.
Figure 7. Graph. Relationship between total access points per mile and crash rate (figure 24 in Gluck, Levinson, and Stover, 1999).^{(3)}
Figure 8. Graph. Relationship between access points per mile and crash rate (figure 26 in Gluck, Levinson, and Stover, 1999).^{(3)}
Figure 9. Graph. Relationship between signals per mile and crash rate (figure 6 in Gluck, Levinson, and Stover, 1999).^{(3)}
Figure 10. Photo. Example of an urban arterial in a residential area.
Figure 11. Photo. Example of a suburban arterial in a commercial area.
Figure 12. Illustrations and photos. Verifying HSIS data with aerial photos.^{(15)}
Figure 13. Screen shot. Verifying data with aerial imagery.^{(16)}
Figure 14. Photo. Verifying data with video.
Figure 15. Image. Example of point objects for a 1mi corridor.^{(17)}
Figure 16. Photo. Data collection equipment used for field visit.
Figure 17. Equation. General form of crash prediction model.
Figure 18. Equation. Crash prediction model with regional calibration.
Figure 19. Equation. Normalized crash prediction model with regional calibration.
Figure 20. Equation. Formula to estimate effects of variables of interest for existing conditions.
Figure 21. Equation. Formula to estimate w.
Figure 22. Equation. Formula to estimate the annual expected crash frequency (EB estimate).
Figure 23. Equations. Calculation of predicted rightangle crashes/year (existing).
Figure 24. Equations. Calculation of predicted rightangle crashes/year (proposed).
Figure 25. Equations. Effect of ACCDENS: predicted total crashes/year (existing).
Figure 26. Equations. Effect of ACCDENS: predicted total crashes/year (proposed).
Figure 27. Equations. Effect of PROPNODEV: predicted total crashes/year (existing).
Figure 28. Equations. Effect of PROPNODEV: predicted total crashes/year (proposed).
Figure 29. Equations. Total crashes: predicted total crashes/year (existing).
Figure 30. Equations. Total crashes: predicted crashes/year (proposed).
Figure 31. Equations. Turning crashes: predicted turning crashes/year (existing).
Figure 32. Equations. Turning crashes: predicted turning crashes/year (proposed).
Figure 33. Equations. Rightangle crashes: predicted rightangle crashes/year (existing).
Figure 34. Equations. Rightangle crashes: predicted rightangle crashes/year (proposed).
Figure 35. Equations. Baseline predicted rightangle crashes/year (existing alternative A).
Figure 36. Equations. Estimate of w.
Figure 37. Equations. Expected rightangle crashes/year (existing alternative A).
Figure 38. Equation. Estimate EB correction factor.
Figure 39. Equations. Predicted rightangle crashes/year (existing alternative A).
Figure 40. Equations. Predicted rightangle crashes/year (proposed alternative B).
Figure 41. Equations. Predicted rightangle crashes/year (proposed alternative C).
Figure 42. Equations. Adjusted predicted rightangle crashes/year for existing condition.
Figure 43. Equations. Expected rightangle crashes/year for proposed condition.
Figure 44. Equations. Baseline predicted rightangle crashes/year (existing).
Figure 45. Equation. Estimate of the impacts of the variables of interest for existing conditions.
Figure 46. Equations. Estimation of multipliers.
Figure 47. Equations. Adjusted predicted rightangle crashes/year (existing alternative A).
Figure 48. Equations. Estimation of multipliers.
Figure 49. Equations. Adjusted predicted rightangle crashes/year (proposed alternative B).
Figure 50. Equation. Estimated calibration factor.
Figure 51. Equation. Original multiplier.
Figure 52. Equation. Estimation of calibrated multiplier.
Figure 53. Equations. Minnesota crash prediction model.
Table 1. Prioritization of AM policies and techniques.
Table 2. Strategies/policies in relation to AM safety principles (adapted from V.G. Stover, 2007).^{(1)}
Table 3. Area type and land use categories.
Table 4. Potential issues and opportunities related to crosssectional studies.
Table 5. Objects and characteristics coded in ArcGIS™.
Table 6. Number of corridors by area type and land use.
Table 7. Mileage of corridors by area type and land use.
Table 8. Crash type definitions.
Table 9. North Carolina mileage by area type and land use.
Table 10. Summary statistics for North Carolina independent variables.
Table 11. Summary statistics for North Carolina dependent variables.
Table 12. Northern California mileage by area type and land use.
Table 13. Summary statistics for Northern California independent variables.
Table 14. Summary statistics for Northern California dependent variables.
Table 15. Southern California mileage by area type and land use.
Table 16. Summary statistics for Southern California independent variables.
Table 17. Summary statistics for Southern California dependent variables.
Table 18. Minnesota mileage by area type and land use.
Table 19. Summary statistics for Minnesota independent variables.
Table 20. Summary statistics for Minnesota dependent variables.
Table 21. Overview of mixeduse models by crash type.
Table 22. Overview of commercial models by crash type.
Table 23. Overview of residential models by crash type.
Table 24. Relevant models by crash type of interestâ€”mixed land use.
Table 25. Relevant models by crash type of interestâ€”commercial land use.
Table 26. Relevant models by crash type of interestâ€”residential land use.
Table 27. Correlation coefficients for MINSPCSIG (model coefficient, pvalue).
Table 28. Correlation coefficients for NOLTLSIG (model coefficient, pvalue).
Table 29. Driveway density CMFs inferred from the Highway Safety Manual predictive models for multivehicle crashes on urban fourlane undivided and divided arterials.^{(22)}
Table 30. Comparison of implied CMFs for SIGDENS.
Table 31. HSIS data obtained for California.
Table 32. HSIS data obtained for Minnesota.
Table 33. HSIS data obtained for North Carolina.
Table 34. Alternate model 1 for mixeduse total crashes.
Table 35. Alternate model 2 for mixeduse total crashes.
Table 36. Alternate model 3 for mixeduse total crashes.
Table 37. Alternate model 1 for mixeduse injury crashes.
Table 38. Alternate model 2 for mixeduse injury crashes.
Table 39. Alternate model 1 for mixeduse turning crashes.
Table 40. Alternate model 2 for mixeduse turning crashes.
Table 41. Alternate model 3 for mixeduse turning crashes.
Table 42. Alternate model 1 for mixeduse rearend crashes.
Table 43. Alternate model 2 for mixeduse rearend crashes.
Table 44. Alternate model 1 for mixeduse rightangle crashes.
Table 45. Alternate model 2 for mixeduse rightangle crashes.
Table 46. Alternate model 3 for mixeduse rightangle crashes.
Table 47. Alternate model 1 for commercial total crashes.
Table 48. Alternate model 2 for commercial total crashes.
Table 49. Alternate model 1 for commercial injury crashes.
Table 50. Alternate model 2 for commercial injury crashes.
Table 51. Alternate model 3 for commercial injury crashes.
Table 52. Alternate model 4 for commercial injury crashes.
Table 53. Alternate model 1 for commercial turning crashes.
Table 54. Alternate model 2 for commercial turning crashes.
Table 55. Alternate model 1 for commercial rearend crashes.
Table 56. Alternate model 2 for commercial rearend crashes.
Table 57. Alternate model 1 for commercial rightangle crashes.
Table 58. Alternate model 2 for commercial rightangle crashes.
Table 59. Alternate model 1 for residential total crashes.
Table 60. Alternate model 2 for residential total crashes.
Table 61. Alternate model 3 for residential total crashes.
Table 62. Alternate model 4 for residential total crashes.
Table 63. Alternate model 1 for residential injury crashes.
Table 64. Alternate model 2 for residential injury crashes.
Table 65. Alternate model 1 for residential turning crashes.
Table 66. Alternate model 2 for residential turning crashes.
Table 67. Alternate model 3 for residential turning crashes.
Table 68. Alternate model 4 for residential turning crashes.
Table 69. Alternate model 1 for residential rearend crashes.
Table 70. Alternate model 2 for residential rearend crashes.
Table 71. Alternate model 3 for residential rearend crashes.
Table 72. Alternate model 1 for residential rightangle crashes.
Table 73. Alternate model 2 for residential rightangle crashes.
Table 74. Alternate model 3 for residential rightangle crashes.
Table 75. Summary statistics for North Carolina mixeduse land use.
Table 76. Summary statistics for Minnesota mixeduse land use.
Table 77. Summary statistics for Northern California mixeduse land use.
Table 78. Summary statistics for Southern California mixeduse land use.
Table 79. Summary statistics for North Carolina commercial land use.
Table 80. Summary statistics for Minnesota commercial land use.
Table 81. Summary statistics for Northern California commercial land use.
Table 82. Summary statistics for Southern California commercial land use.
Table 83. Summary statistics for North Carolina residential land use.
Table 84. Summary statistics for Minnesota residential land use.
Table 85. Summary statistics for Northern California residential land use.
Table 86. Summary statistics for Southern California residential land use.
Table 87. Correlation coefficients for mixed land use.
Table 88. Correlation coefficients for commercial land use.
Table 89. Correlation coefficients for residential land use.
4D  fourlane divided arterial 
4U  fourlane undivided arterial 
AADT  annual average daily traffic 
AASHTO  American Association of State Highway and Transportation Officials 
ACCDENS  number of driveways plus unsignalized intersections per mile 
ADT  average daily traffic 
AM  access management 
AVGAADT  average of the annual average daily traffic 
b  coefficient estimated for the annual average daily traffic term in the models 
ci  vector of coefficients estimated for independent variables included in the models 
CMF  crash modification factor 
DRWYDENS  number of driveways per mile 
EB  empirical Bayes 
FHWA  Federal Highway Administration 
GIS  Geographic Information System 
GLM  generalized linear modeling 
GPS  Global Positioning System 
HSIS  Highway Safety Information System 
ID  identity 
k  dispersion parameter 
MAXSPCSIG  maximum spacing of signalized intersections 
MEDOPDENS  number of median openings per mile 
MEDOPLT  number of median openings with a leftturn lane 
MEDOPNOLT  number of median openings without a leftturn lane 
MINSPCSIG  minimum spacing of signalized intersections 
MVMT  million vehiclemiles traveled 
NO3LEGFULLUNSIG  number of threelegged fullmovement unsignalized intersections 
NO3LEGLFMOUNSIG  number of threelegged unsignalized intersections with no leftturn movement from crossroad 
NO3LEGLIMUNSIG  number of threelegged limitedmovement unsignalized intersections 
NO3LEGRIROUNSIG  number of threelegged rightin/rightout unsignalized intersections 
NO3LEGSIG  number of threelegged signalized intersections 
NO3LEGUNSIG  number of threelegged unsignalized intersections 
NO4LEGFULLUNSIG  number of fourlegged fullmovement unsignalized intersections 
NO4LEGLFMOUNSIG  number of fourlegged unsignalized intersections with no leftturn movement from crossroad 
NO4LEGLIMUNSIG  number of fourlegged limitedmovement unsignalized intersections 
NO4LEGRIROUNSIG  number of fourlegged rightin/rightout unsignalized intersections 
NO4LEGSIG  number of fourlegged signalized intersections 
NO4LEGUNSIG  number of fourlegged unsignalized intersections 
NO5LEGSIG  number of fivelegged signalized intersections 
NO5LEGUNSIG  number of fivelegged unsignalized intersections 
NOCOMFULLDRWY  number of commercial fullmovement driveways 
NOCOMLIMDRWY  number of commercial limitedmovement driveways 
NODRWYS  number of driveways 
NOLTLSIG  number of signalized intersections with a leftturn lane on the mainline 
NOLTLUNSIG  number of unsignalized intersections with a leftturn lane 
NOMEDOP  number of median openings 
NOMEDOPLT  number of median openings with a leftturn lane 
NOMEDOPNOLT  number of median openings without a leftturn lane 
NORESFULLDRWY  number of residential fullmovement driveways 
NORESLIMDRWY  number of residential limitedmovement driveways 
NORTLSIG  number of signalized intersections with a rightturn lane on the mainline 
NORTLUNSIG  number of unsignalized intersections with a rightturn lane 
NOSIG  number of signalized intersections 
NOUNSIG  number of unsignalized intersections 
PC  personal computer 
PROPDIV  proportion of corridor length with divided median 
PROPFRONTRD  proportion of corridor length with a frontage road 
PROPFULLDEV  proportion of corridor length with full roadside development 
PROPLANE1  proportion of corridor length with two lanes 
PROPLANE2  proportion of corridor length with three or four lanes 
PROPLANE3  proportion of corridor length with five or more lanes 
PROPLIGHT  proportion of corridor length with illumination present 
PROPLIMCONN  proportion of corridor length with limited connectivity on adjacent developments 
PROPMODCONN  proportion of corridor length with moderate connectivity on adjacent developments 
PROPNODEV  proportion of corridor length with no roadside development 
PROPPARTDEV  proportion of corridor length with partial adjacent development 
PROPPOORPVMNT  proportion of corridor length with a poor pavement condition 
PROPSIGCONN  proportion of corridor length with significant connectivity on adjacent developments 
PROPTWLTL  proportion of corridor length with twoway leftturn lane 
PROPUNDIV  proportion of corridor length with an undivided median 
PROPVC  proportion of corridor length with visual clutter 
SIGDENS  number of signalized intersections per mile 
SPCOFFLT  minimum spacing from offramp to available left turn onto mainline from same side of road 
SPCOFFRT  minimum spacing from offramp to available right turn onto mainline from same side of road 
SPCON  minimum spacing from onramp to available right turn onto mainline from same side of road 
SPEED_ LIMIT  posted speed limit 
TWLTL  twoway leftturn lane 
UNSIGDENS  number of unsignalized intersections per mile 
USGS  United States Geological Survey 
vpd  vehicles per day 
w  EB weight 
X_{i}  vector of independent variables included in the model 