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Publication Number: FHWA-RD-03-094
Date: March 2005

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

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Foreword

In 1998, the Federal Highway Administration (FHWA) sponsored a two–phase study to develop traffic load estimates for Long–Term Pavement Performance (LTPP) sites. This report describes the results of the Phase 2 study. The Phase 1 study resulted in the development of methodology for estimating axle load spectra for all years the LTPP sites were in service. Phase 2 used this methodology to estimate axle loads for all LTPP sites that had acceptable site–specific axle weight data. In total, traffic load estimates were made for 558 LTPP traffic sites.

This report will be of interest to engineers involved in pavement management, design, maintenance, and rehabilitation and in traffic data collection and analysis.

T. Paul Teng, P.E.
Director, Office of Infrastructure
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high–quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

 

Technical Report Documentation Page

1. Report No.
FHWA-RD-03-094
2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle
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

5. Report Date
March 2005
6. Performing Organization
7. Author(s)
Jerry J. Hajek, Olga I. Selezneva, Goran Mladenovic, and Y. Jane Jiang
8. Performing Organization Report No.

9. Performing Organization Name and Address
ERES Consultants, Inc.
9030 Red Branch Road, Suite 210
Columbia, MD 21045

10. Work Unit No.

11. Contract or Grant No.
DTFH61-96-C-00003

12. Sponsoring Agency Name and Address
Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, Virginia 22101-2296
13. Type of Report and Period Covered
Final Report
14. Sponsoring Agency Code

15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): Cheryl Allen Richter, HRDI
Work was conducted as part of the LTPP Data Analysis Technical Support Contract.

16. Abstract

In 1998, the Federal Highway Administration sponsored a study to estimate traffic loads on Long–Term Pavement Performance (LTPP) sites. This report contains findings of the second phase of the study. Phase 1 encompassed the development of the estimation methodology, including numerical examples, and was documented in report FHWA-RD-00-054 issued in July 2000. Phase 2, described in this report, included the assessment of the overall quality of traffic data for all 890 LTPP traffic sites, and the projection of axle loads for all LTPP sites with adequate traffic data. Phase 2 also included the distribution of comprehensive traffic data reports to all participating agencies and the incorporation of comments regarding traffic projections received from the agencies.

Axle load projections were developed for all in-service years up to 1998 for 558 LTPP traffic sites that had adequate traffic monitoring data in the IMS database. The axle load projections were expressed as annual axle load spectra for single, tandem, and triple axles, and were placed into IMS computed parameter tables. The projection results for all LTPP sites are summarized in appendix A.

To overcome the difficulty of estimating traffic loads for the remaining 332 LTPP sites, it was proposed to develop the LTPP Pavement Loading Guide (PLG). The report contains a description of the purpose, design parameters, and functionality of the PLG, a blueprint for the development of the PLG, and two examples of using the PLG to obtain traffic load projections for LTPP sites without site-specific truck class and/or axle load data.

The recommended traffic analysis activities include the development of the LTPP PLG, completing traffic load projections for all LTPP sites, and the development of a comprehensive action plan for better utilization of the existing traffic data. The recommended components of the action plan include a comprehensive quality assurance process, use of monthly traffic data for estimating traffic loads, and regional traffic modeling utilizing both LTPP traffic data and other traffic data.

17. Key Words
Pavements, traffic estimates, axle loads, LTPP
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages
133
22. Price

Form DOT F 1700.7
Reproduction of completed page authorized

 

SI* (Modern Metric) Conversion Factors


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

FHWA-RD-03-094

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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