ESTIMATING CUMULATIVE TRAFFIC LOADS, Volume II:
Traffic Data Assessment and Axle Load Projection for the Sites with Acceptable Axle Weight Data
Final Report for Phase 2

TABLE OF CONTENTS

• CHAPTER 1. INTRODUCTION
• Objectives of Phase 2
  Background
  Results of Phase 1
  Report Overview
• CHAPTER 2. PROCEDURES FOR TRAFFIC DATA ASSESSMENT AND PROJECTION
• Step 1-Preliminary Assessment of LTPP Traffic Data
  • Step 2-Development of LTPP Traffic Projection Procedure
  • Step 3-Validation of the LTPP Projection Procedure Using Case Studies
  • Step 4-Development of LTPP Traffic Feedback and Resolution Package
  • Step 5-Preparation of LTPP Traffic Feedback and Resolution Packages for All Participating Agencies
  • Step 6-Review of LTPP Traffic Feedback and Resolution Packages by RCOs
  • Step 7-Review of LTPP Traffic Feedback and Resolution Packages by Participating Agencies
  • Step 8-Implementation of Review Comments Received from Participating Agencies
• CHAPTER 3. RESULTS OF DATA ASSESSMENT AND TRAFFIC PROJECTION
  • Availability of Traffic Projections
  • Scope of the LTPP Traffic Data
  • Historical Trends in LTPP Traffic Data Quantity and Quality
  • Data Analysis/Operations Feedback Reports
• CHAPTER 4. COMPUTED PARAMETER TABLES FOR PROJECTED TRAFFIC DATA
  • Description of Computed Parameter Tables
  • Generation of Projected Annual Axle Load Spectra
• CHAPTER 5. PROTOTYPE LTPP PAVEMENT LOADING GUIDE
  • The Need to Estimate Missing Traffic Data
  • The Need to Assess the Quality of Monitoring Traffic Data
  • Scope of Pavement Loading Guide: LTPP PLG or General PLG
  • Objectives of the PLG and Purpose of This Chapter
  • Role of PLG in Traffic Projection
  • Conceptual Outline of PLG
  • Functionality of LTPP PLG
  • Development of Generic Truck Characteristics and Data-Selection Guidelines
  • Prototype Demonstration Software
  • Example Use of PLG
• CHAPTER 6. SUMMARY AND RECOMMENDATIONS
  • Summary
  • Conclusions
  • Recommendations
• APPENDIX A
• REFERENCES
• LIST OF FIGURES
  1. Overview of main traffic data assessment and projection activities
  2. Initial site-specific report for Mississippi
  3. Feedback and Data Resolution Sheet for site 285805
  4. Site map for site 285805
  5. Annual Traffic Projection Sheet for site 285805
  6. Projected AADT volumes for site 285805
  7. Annual vehicle class distribution for site 285805
  8. Annual load spectra for site 285805
  9. Average annual load spectrum for site 285805
  10. Projected annual ESALs for site 285805
  11. Projection of truck volumes using historical and monitoring data
  12. Comparison of AADT volumes for Class 14 vehicles with AADT volumes for all trucks
  13. Use of the mean of all annual axle load spectra to obtain base annual spectrum
  14. Use of the mean of 1991, 1992, and 1995 annual axle load spectra to obtain base annual spectrum50
  15. Use of the mean of 1991 and 1992 annual axle load spectra to obtain base annual spectrum
  16. Rejection of all available annual axle load spectra
  17. Projected AADT truck volumes for site 124057
  18. Annual Traffic Projection Sheet for site 063042
  19. Projected AADT truck volumes (initial) for site 473104
  20. Summary of LTPP sites sorted by data presence and data usability for projection
  21. Geographical distribution of LTPP sites with acceptable projection confidence codes
  22. Mean vehicle class distribution for LTPP sites with acceptable and questionable projection confidence codes located on rural highways
  23. Mean vehicle class distribution for LTPP sites with acceptable and questionable projection confidence codes located on urban highways
  24. Trends in the number of monitoring axle load spectra
  25. Overview of the IMS Traffic Module showing the proposed addition of projected traffic data
  26. Flowchart used for calculating computed parameter tables
  27. Flowchart for computation of the normalized base annual load spectra
  28. Flowchart for computation of the base annual axle load summary
  29. Flowchart for computation of the annual projection factors
  30. Flowchart for computation of projected annual axle load spectra
  31. Overview of PLG functions
  32. Comparison of truck class distributions for sites 062040, 066044, and 068150
  33. Comparison of single axle load distributions for vehicle Class 9 for sites 062040 and 066044 with computed mean distribution
  34. Comparison of tandem axle load distributions for vehicle Class 9 for sites 062040 and 066044 with computed mean distribution
  35. Comparison of site-specific and surrogate base annual spectra for site 068150
  36. Comparison of projected, historical, and monitoring annual ESALs for site 068150
  37. Comparison of truck class distributions for sites 041007 and 041017
  38. Comparison of site-specific and surrogate base annual spectra for 041017
  39. Comparison of projected, historical, and monitoring annual ESALs for site 041017
• LIST OF TABLES
  1. FHWA commercial vehicle classification schema
  2. Example of possible axle-per-class coefficients for Class 9 vehicles
  3. Arizona LTPP sites near other sites on the same highway and in the same direction
  4. Traffic loading parameters for Mississippi LTPP sites with axle weight projections
  5. Traffic loading parameters for Mississippi sites without axle weight projections
  6. Characteristic values of axle load spectra
  7. Availability of traffic projections
  8. Availability of traffic projections by experiment type and projection confidence code
  9. Availability of traffic projections by highway functional class and projection confidence codes
  10. Presence of traffic data by LTPP region
  11. Availability of traffic projections by LTPP region and projection confidence codes
  12. Availability of traffic projections by participating agencies and projection confidence codes
  13. Traffic characteristics of LTPP sites with acceptable and questionable projection confidence codes
  14. Truck class distribution by highway functional classes for LTPP sites with acceptable and questionable projection confidence codes
  15. Availability of annual axle weight data and their use for projection
  16. Summary of data analysis/operations feedback report prepared during the study
  17. List of main variables stored in PLG
  18. Example of truck class distribution
  19. Codes in the IMS database
  20. Code indicating projection category (2 to 5)
  21. Summary of traffic projection results