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LIST OF TABLES (CONT.)

Table 28b. Truck directional and lane distribution factors from the region for Roadway B ....................................................................................................84

Table 28c. Truck directional and lane distribution factors from the region for Roadway C ....................................................................................................84

Table 29. Traffic characteristics for example problems ....................................................................................................85

Table 30a. Normalized truck distribution spectra from the region/state for Roadway A ....................................................................................................85

Table 30b. Normalized truck distribution spectra from the region/state for Roadway B ....................................................................................................85

Table 30c. Normalized truck distribution spectra from the region/state for Roadway C ....................................................................................................85

Table 31. Representative truck distribution spectrum for Roadways A, B and C ....................................................................................................86

Table 32a. Seasonal (monthly) distribution factors from the region for Roadway A ....................................................................................................89

Table 32b. Seasonal (monthly) distribution factors from the region for Roadway B ....................................................................................................89

Table 32c. Seasonal (monthly) distribution factors from the region for Roadway C ....................................................................................................90

Table 33a. Time of day distribution factors for Level 3 design for Roadways A ....................................................................................................92

Table 33b. Time of day distribution factors for Level 3 design for Roadways B ....................................................................................................93

Table 33c. Time of day distribution factors for Level 3 design for Roadways C ....................................................................................................93

Table 34. Traffic characteristics used for Level 4 inputs for example problems ....................................................................................................94

Table 35. Comparison of the differences among the levels of inputs for selected axle load groups using the average daily traffic ....................................................................................................96

Table 36. Number of 80kN Equivalent Single Axle Loads computed (using AASHTO load equivalency factors) for the first year for the four input levels for each example problem ....................................................................................................96

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Acknowledgment of Sponsorship

This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO) in cooperation with the Federal Highway Administration and was conducted in the National Cooperative Highway Research Program which is administered by the Transportation Research Board of the National Research Council.

Disclaimer

This is the final draft as submitted by the research agency. The opinions and conclusions expressed or implied in this report are those of the research agency. They are not necessarily those of the Transportation Research Board, the National Research Council, the Federal Highway Administration, AASHTO, or the individual States participating in the National Cooperative Highway Research program.

Acknowledgements

The research team for NCHRP Project 1-37A: Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures consisted of Applied Research Associates, Inc., ERES Consultants Division (ARA-ERES) as the prime contractor with Arizona State University (ASU) as the primary subcontractor. Fugro-BRE, Inc., the University of Maryland, and Advanced Asphalt Technologies, LLC served as subcontractors to either ARA-ERES or ASU along with several independent consultants.

Research into the subject area covered in this Appendix was conducted at ARA-ERES and Fugro-BRE Inc. The authors of this Appendix are Harold L. Von Quintus, Weng On Tam, and Nasir Gharaibeh. Mark Hallenbeck with the Washington State Transportation Center - University of Washington served as a project consultant. John Hallin (ARA-ERES), Matthew Witzak (ASU) and Mike Darter (ARA-ERES) provided an oversight of all activities as project team leaders.

Foreword

The purpose of this document is two-fold. The first objective is to present and discuss the traffic module of the Design Guide software which provides traffic information and input data that are needed for the incremental damage computations in predicting load related distresses. The second objective is to present the data analyses and research that were completed to support the assumptions made in developing the traffic module and for determining the default values when sufficient traffic data are unavailable to the user or designer.

The document is divided into five chapters and supported by eleven sub-appendices. It is a supporting reference to traffic related discussions presented in PART 2, Chapters 4, and PART 3, Chapters 3, 4, 6, and 7 of the Design Guide.

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1 – INTRODUCTION	1
Background	1
Purpose of Document	2
Scope of Document	2
2 – GENERAL OVERVIEW – APPROACH AND METHODOLOGY	3
Flexibility and User Interaction: Focus on Implementation	3
Hierarchical Approach: Design/Analysis Levels of Varying Detail	3
Traffic Module Data Analyses	5
Truck Traffic Classification: Functional Versus Structural	7
Assumptions	8
Module Operational Functions and Designer Decisions	9
3 – TRAFFIC DEFAULT VALUES	17
Acquisition and Processing of LTPP Data	17
Evaluation of AVC Data	24
Truck Traffic Classifications for Pavement Design	39
Evaluation of WIM Data	54
Evaluation of Tire Dimensions and Inflation Pressures	64
Wander – Lateral Distribution of Trucks	72
Growth Rate of Trucks	72
4 – OVERALL ACCURACY IN TRAFFIC PREDICTIONS	73
Calculation of the Expected Error in the Traffic Estimates	73
Traffic Sampling Plan Requirements	73
5 – EXAMPLES/DEMONSTRATIONS OF THE TRAFFIC MODULE	76
Processing and Evaluation of AVC Data	76
Processing and Evaluation of WIM Data	77
Level 1 Inputs for the Example Problems	77
Level 2 Inputs for the Example Problems	83
Level 3 Inputs for the Example Problems	83
Level 4 Inputs for the Example Problems	93
Program Execution and Output	95
REFERENCES	97

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APPENDICES

APPENDIX AA.1 – FLOWCHART ILLUSTRATING THE TRAFFIC ANALYSES

APPENDIX AA.2 – NORMALIZED TRUCK CLASS DISTRIBUTION

APPENDIX AA.3 – DEFAULT VALUES SUGGESTED FOR USE FOR EACH TRUCK TRAFFIC CLASSIFICATION

APPENDIX AA.4 – NORMALIZED ANNUAL AXLE WEIGHT DISTRIBUTIONS/SPECTRA

APPENDIX AA.5 – NORMALIZED AXLE WEIGHT STATISTICS FOR VEHICLE CLASSES 5 AND 9 FOR SELECTED SITES

APPENDIX AA.6 – NORMALIZED MONTHLY AXLE LOAD SPECTRA FOR FIVE SITES

APPENDIX AA.7 – DEFAULT NORMALIZED AXLE LOAD SPECTRA

APPENDIX AA.8 – NORMALIZED AXLE LOAD SPECTRA FOR LEVEL 1 INPUTS FOR THE EXAMPLE PROBLEMS

APPENDIX AA.9 – AXLE LOAD SPECTRA FROM OTHER ROADWAYS USED TO DETERMINE THE REGIONAL VALUES FOR THE LEVEL 2 AND LEVEL 3 INPUTS TO THE EXAMPLE PROBLEMS

APPENDIX AA.10 – REGIONAL AXLE LOAD SPECTRA USED FOR LEVEL 2 AND LEVEL 3 INPUTS TO THE EXAMPLE PROBLEMS

APPENDIX AA.11 – TABULATION OF A SUMMARY OF THE OUTPUT FROM THE TRAFFIC MODULE FOR THE EXAMPLE PROBLEMS

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LIST OF TABLES

Table 1.	List of information in Level 4 data and their corresponding column numbers	19
Table 2.	AVC temporary array for hourly data	19
Table 3.	WIM temporary array	23
Table 4.	LTPP Sections selected for initial traffic analysis	24
Table 5.	Traffic characteristics for Section 124103	26
Table 6.	Time of day distribution	35
Table 7.	Truck traffic classification criteria	40
Table 8.	Number of sections from each TTC that fall into each functional class	41
Table 9.	Suggested guidance for selecting appointment TTCs for different highway	41
Table 10.	Definitions and descriptions for the truck traffic classifications	42
Table 11.	ρ and β used from the sigmoidal curve equation used to represent the cumulative percentage of the number of axles per weight group	59
Table 12.	ρ and β values determined for each of the default axle load spectra tabulated in Appendix G	63
Table 13.	Axle spacings from Level 4 WIM data, m	65
Table 14.	The tandem axle spacings for various percentiles of the data that were found from an analysis of the LTPP database for vehicle type 352000	66
Table 15.	The average number of single, tandem, tridem axles per truck type	66
Table 16.	List of most commonly used tires and their share of the market	67
Table 17.	Tire widths and minimum dual spacings from TRA year book	68
Table 18.	Tire diameters from TRA yearbook	68
Table 19.	Tire diameters and widths for Bridgestone/Firestone tires	68
Table 20.	Maximum load and corresponding cold inflation pressures	70
Table 21.	Minimum sample size (number of days) to estimate the normalized axle load distribution – WIM data	74
Table 22.	Minimum sample size (number of days) to estimate the normalized vehicle class distribution – AVC data	74
Table 23.	Minimum sample size (number of days) to estimate the total axles per day by month or year – AVC data	75
Table 24.	Projected AADTT for the three example roadways	78
Table 25.	Representative normalized truck distribution spectra used for the example problems	80
Table 26.	Seasonal (monthly) distribution factors used for the example problems	82
Table 27.	Time of day distribution factors	83
Table 28a.	Truck directional and lane distribution factors from the region for Roadway A	84

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