Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home   |   Pavements Home
Report
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-RD-03-041

Evaluation and Analysis of LTPP Pavement Layer Thickness Data

PDF Version (1 MB)

PDF files can be viewed with the Acrobat® Reader®

Foreword

This report documents a comprehensive review and evaluation of the Long Term Pavement Performance (LTPP) pavement layer thickness data. Pavement layer thickness data are very important for many types of analyses, including backcalculation of pavement moduli, mechanistic analysis of pavement structures, and performance modeling. The accuracy of layer thickness data has a great impact on the outcome of practically all analyses of performance. The report contains an assessment of the LTPP layer thickness data and recommendations for resolution of anomalous data. Results of the statistical analyses documented in this report provide insights into the characteristics of within-section layer thickness variability. The results of the comparison between as-designed and as-constructed layer thickness data provide useful estimates of the expected construction-related variability. These results can serve as a very important input to pavement engineering applications involving the reliability of pavement design and also for quality assurance construction specifications.

This report will be of interest to highway agency engineers involved in pavement analysis, design, construction, and data collection, as well as future researchers who will use LTPP data to improve on the design procedures and standards for constructing pavements.

 

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

 

 

Notice

This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.

The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein only because they are considered essential to the objective of this document.


Technical Report Documentation Page
1. Report No.
FHWA-RD-03-041
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle
EVALUATION AND ANALYSIS OF LTPP PAVEMENT LAYER THICKNESS DATA
5. Report Date July 30, 2002
6. Performing Organization
7. Author(s)
Olga I. Selezneva, Y. Jane Jiang, and Goran Mladenovic
8. Performing Organization Report No.
9. Performing Organization Name and Address
ERES Division of Applied Research Associates, Inc.
9030 Red Branch Road, Suite 210
Columbia, Maryland 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 2001, the Federal Highway Administration sponsored a study to review pavement layer thickness data for Long Term Pavement Performance (LTPP) sites. The main objective of the study was to assess the quality and completeness of pavement layering information and layer thickness data and to provide recommendations for improvement. In the course of the study, layer thickness data available in the LTPP database were examined for quality and completeness using Levels A to E data. Following the data completeness evaluation, pavement layering data were evaluated to determine the consistency of material type and thickness data between different data sources.

In addition, layer thickness variability indicators, within-section material type consistency, and material type and thickness reasonableness were evaluated. In the cases where there were inconsistencies in the data, the data were reviewed and reported to the LTPP data managers along with recommendations for data anomaly resolution. In addition, the layer thickness data from Specific Pavement Studies (SPS) experiments were analyzed to determine characteristics of within-section layer thickness variation. The analysis included layers with different material and functional types. Descriptive statistics such as mean, standard deviation, skewness, and kurtosis were computed for each section. The statistical analysis results for 1,034 SPS layers indicated that 84 percent of all layers thickness variations within LTPP section follow a normal distribution.

The extent of differences between as-designed (inventory) and as-constructed (measured) layer thickness data was also investigated for the SPS sections. The results of analysis indicate that about 60 percent of all section/layers have mean thicknesses within 6.35 mm (0.25 in) of the target thickness. For a tolerance level of 25.4 mm (1 in), this percentage is above 90 for most layer types and target thickness values. For the same layer and material type, the mean constructed layer thicknesses tend to be above the designed value for the thinner layers and below the designed value for the thicker layers.

One important product from this study is the Researcher's Guide to LTPP Layer Thickness Data. The main purpose of this guide is to provide guidance for the selection of layer material type and thickness data from the LTPP database. The guide also contains a discussion about within-section layer thickness variability and comparison between as-designed and as-constructed layer thickness. The guide is available as a separate publication.

17. Key Words
Pavements, LTPP, layer thickness, material type, variability, deviations
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
159
22. Price

 

SI* (Modern Metric) Conversion Factors


Table of Contents

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS

  1. INTRODUCTION
    Layer Structure and Thickness Information Collected by the LTPP Program
    Need for Review of LTPP Pavement Layer Thickness Data
    Study Objectives
    Report Organization

  2. ASSESSMENT OF DATA AVAILABILITY AND COMPLETENESS
    LTPP Data Source Used in This Study
    LTPP Data Availability and Quality Control Checks
    Assessment of the LTPP Layer Thickness Data Availability and Completeness
    Summary

  3. EVALUATION OF LAYER STRUCTURE INFORMATION AND THICKNESS DATA REASONABLENESS
    Data Evaluation Overview
    Step 2 - Analysis Data Set
    Step 3 - Layer Functional Description Evaluation
    Step 4 - Material Type Reasonableness and Consistency
    Step 5 - Reasonableness and Consistency of Layer Thickness Data
    Step 7 - Evaluation Outcome Summary and Resolution
    Summary of Pavement Layering Data Evaluation

  4. EVALUATION OF PAVEMENT LAYER THICKNESS VARIABILITY
    Thickness Data Sources
    Evaluation Methodology for Thickness Variability Reasonableness
    Evaluation of the Layer Thickness Variation Reasonableness Using Core Data
    Evaluation of the Layer Thickness Variation Reasonableness Using Elevation Data
    Typical LTPP Layer Thickness Variability Values
    Comparison between Elevation and Core Thickness Measurements
    Summary

  5. CHARACTERIZATION OF LTPP THICKNESS WITHIN-SECTION VARIABILITY
    Data Sources
    SPS Layer Thickness Characteristics
    Goodness-of-Fit between Experimental Data and Theoretical Statistical Distribution
    Summary

  6. CHARACTERIZATION OF VARIATION BETWEEN AS-DESIGNED AND AS-CONSTRUCTED LAYER THICKNESSES
    Data Sources
    Design Thicknesses
    Study Methodology
    Typical Deviations between Mean Measured and the Design Thicknesses
    Statistical Analysis of Elevation Measurements
    Statistical Analysis of the Core Thickness Data
    Summary

  7. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
    Summary and Conclusions
    Recommendations

APPENDIX A - CORRELATED MATERIAL CODES

APPENDIX B - SKEWNESS AND KURTOSIS TEST
Statistical Formulations Used in the Skewness and Kurtosis Test

APPENDIX C - KOLMOGOROV-SMIRNOV GOODNESS-OF-FIT TEST
Procedures for the Kolmogorov-Smirnov Goodness-of-fit Test
Results of the Kolmogorov-Smirnov Goodness-of-fit Tests

REFERENCES

LIST OF TABLES

Table 1. Data availability assessment of the regular sections for layer thickness related tables.

Table 2. Data availability assessment for layer thickness related tables for supplemental sections.

Table 3. List of pavement structures that do not have any data in either the TST_L05B table or the TST_L05A table at any QC level.

Table 4. Level E data availability for layer thickness-related tables for LTPP experiments.

Table 5. Evaluation of layer numbering correspondence between the INV_LAYER and TST_L05B tables.

Table 6. Summary of the number of records used in the cross-table pavement layering analysis.

Table 7. LTPP layer function description codes.

Table 8. Summary of the layer functional description consistency evaluation.

Table 9. Criteria for evaluation of material code validity.

Table 10. Summary of the records with erroneous material codes.

Table 11. Material type consistency criteria.

Table 12. Summary of the layer material type consistency evaluation.

Table 13. Summary of the layer material type consistency evaluation along the LTPP section length (TST_L05A table).

Table 14. Thickness ranges used for reasonableness checks.

Table 15. Summary of the layer thickness reasonableness evaluation results1.

Table 16. Criteria used for evaluation of layer thickness consistency between different tables.

Table 17. Summary of the layer thickness consistency evaluation results1.

Table 18. Summary of layering data consistency evaluation for each LTPP experiment.

Table 19. Summary of project-level layer thickness variability evaluation using core data.

Table 20. Core data availability in tables TST_AC01_LAYER and TST-PC06.

Table 21. Summary of the elevation thickness measurements in the SPS*_LAYER_THICKNESS tables.

Table 22. The distribution of the elevation thickness records not used in the analysis.

Table 23. Distribution of the outliers by layer type.

Table 24. Summary of project-level layer thickness variability evaluation using elevation grid data.

Table 25. Summary of layer thickness COV and standard deviations based on core measurements.

Table 26. Summary of layer thickness COV and standard deviations based on SPS elevation measurements.

Table 27. Summary of layers with both elevation and core data available.

Table 28. Comparison of variances (F-test, 99 percent confidence level) obtained from elevation and core thickness measurements.

Table 29. Results of the comparison of means (t-test, 95 % confidence level) for elevation and core thickness measurements.

Table 30. Pavement layer and material type identifiers available in the SPS*_LAYER_THICKNESS tables.

Table 31. Design thicknesses for different SPS experiments sorted by layer and material type.

Table 32. Multiplier for the standard deviation used in the outlier criterion based on t-distribution.

Table 33. Descriptive statistics for the binder course layer, SPS-6 section 40_0608.

Table 34. Identified outlier points.

Table 35. Evaluation summary of the goodness-of-fit testing methods.

Table 36. Kurtosis and skewness test results summary for binder course layer, SPS-6 Section 40_0608.

Table 37. Summary of the normality evaluation results.

Table 38. Design layer thicknesses for the SPS-1 experiment.

Table 39. Design layer thicknesses for the SPS-2 experiment.

Table 40. Design layer thicknesses for the SPS-5 experiment.

Table 41. Design layer thicknesses for the SPS-6 experiment.

Table 42. Design layer thicknesses for the SPS-7 experiment.

Table 43. Design layer thicknesses for the SPS-8 experiment.

Table 44. Summary of differences between mean elevation thickness measurements and target thicknesses.

Table 45. Summary of differences between mean core thickness measurements and target thicknesses.

Table 46. Distribution of the mean thickness deviations from the design thickness based on kurtosis and skewness tests.

Table 47. Percentage distribution summary of the elevation thickness measurements.

Table 48. Percentage distribution of individual elevation measurements by layer type and design thickness for a tolerance level of 6.35 mm (0.25 in).

Table 49. Percentage distribution of individual elevation measurements by layer type and design thickness for a tolerance level of 12.7 mm (0.5 in).

Table 50. Percentage distribution of individual elevation measurements by layer type and design thickness for a tolerance level of 25.4 mm (1 in).

Table 51. Summary of the results of the two-sided t-tests (95 percent confidence level) using elevation measurements.

Table 52. Results of the two-sided t-test for different material types (95 percent confidence level) by layer type and design thickness using elevation measurements.

Table 53. Summary of the results of one-sided t-tests using elevation measurements.

Table 54. Results of one-sided t-test for tolerance level of 6.35 mm (0.25 in) by layer type and design thickness using elevation measurements.

Table 55. Results of one-sided t-tests for tolerance level of 12.7 mm (0.5 in) by layer type and design thickness using elevation measurements.

Table 56. Results of one-sided t-test for tolerance level of 25.4 mm (1 in) by layer type and design thickness using elevation measurements.

Table 57. Summary of the percentage distribution of the individual core thickness measurements versus the design thickness.

Table 58. Percentage distribution of core thickness measurements by layer type and design thickness for a tolerance level of 6.35 mm (0.25 in).

Table 59. Percentage distribution of core thickness measurements by layer type and design thickness for a tolerance level of 12.7 mm (0.5 in).

Table 60. Percentage distribution of core thickness measurements by layer type and design thickness for a tolerance level of 25.4 mm (1 in).

Table 61. Summary of the results of the two-sided t-test (95 percent confidence level) using core thickness data.

Table 62. Distribution of differences by layer type and design thickness (two-sided t-test, 95 percent confidence level) using core thickness data.

Table 63. Summary of the results of the one-sided t-tests using core thickness data.

Table 64. Results of the one-sided t-test (95 percent confidence level) by layer type and design thickness for tolerance level of 6.35 mm (0.25 in) using core thickness data.

Table 65. Results of the one-sided t-test (95 percent confidence level) by layer type and design thickness for tolerance level of 12.7 mm (0.5 in) using core examination data.

Table 66. Results of the one-sided t-test (95 percent confidence level) by layer type and design thickness for tolerance level of 25.4 mm (1 in) using core examination data.

Table 67. Correlated material codes.

Table 68. Number of pavement layers and number of layer thickness measurements per layer grouped by material and layer type.

Table 69. Summary of the goodness-of-fit results using Kolmogorov-Smirnov test with 1 percent level of significance.

LIST OF FIGURES

Figure 1: Graph. LTPP data sources containing pavement layering data.

Figure 2: Graph. Four essential pavement layering characteristics.

Figure 3: Chart. Flowchart for pavement layering data evaluation.

Figure 4: Graph. Example of layer functional description consistency evaluation.

Figure 5: Chart. Results of layer functional description consistency evaluation.

Figure 6: Graph. Example of evaluation of layer material type consistency between different tables.

Figure 7: Chart. Results of layer material type consistency evaluation between different data sources.

Figure 8: Graph. Example of evaluation of layer material type consistency along the section.

Figure 9: Chart. Results of layer material type consistency evaluation along the section.

Figure 10: Graph. Example of evaluation of layer thickness consistency between different data tables.

Figure 11: Chart. Results of layer thickness consistency evaluation between different data sources.

Figure 12: Graph. Location of core sampling and elevation measurement areas along the LTPP section.

Figure 13: Equation. Definition of coefficient of variation.

Figure 14: Equation. The null and alternative hypotheses for the F-test.

Figure 15: Equation. The null and alternative hypotheses for the t-test.

Figure 16: Chart. Comparison of the standard deviation for core thickness and elevation measurements.

Figure 17: Chart. Comparison of the COV for core thickness and elevation measurements.

Figure 18: Chart. Results of the statistical analysis of differences between elevation and core thickness measurements.

Figure 19: Chart. Example of the binder course thickness measurements along SPS-6 Section 40_0608 with an apparent outlier.

Figure 20: Equation. Outlier definition criterion.

Figure 21: Chart. Example of the AC surface and binder layer thickness distribution with clear outlier detection for the SPS-1 Section 30-0112.

Figure 22: Chart. Example of dense graded aggregate base layer thickness distribution with questionable outlier detection for the SPS-2 Section 20-0210.

Figure 23: Chart. Example of the dense graded aggregate base layer thickness distribution skewed to the left for the SPS-1 Section 20-0101.

Figure 24: Chart. Example of the normal layer thickness distribution for PCC surface layer, SPS-2, Section 10_0211.

Figure 25: Chart. Example of the uniform layer thickness distribution for dense graded aggregate base, SPS-1, Section 12_0101.

Figure 26: Chart. Example of the layer thickness distribution skewed to the right for PCC surface layer, SPS-2, Section19_0213.

Figure 27: Chart. Flowchart of the kurtosis and skewness test procedures used for the test of layer thickness distribution normality.

Figure 28: Equation. Definition of p-values.

Figure 29: Chart. Example distribution of layer thickness measurements along the section for the DGAB layer for the SPS-1 Section 35-0108.

Figure 30: Chart. Example distribution of layer thickness measurements along the section for the DGAB layer for the SPS-2 Section 19-0214.

Figure 31: Chart. Example distribution of layer thickness measurements along the section for the DGAB layer for the SPS-8 Section 08-0811.

Figure 32: Chart. Example distribution of layer thickness measurements along the section for the DGATB layer for the SPS-1 Section 22-0118.

Figure 33: Chart. Example distribution of layer thickness measurements along the section for the LC base layer for the SPS-2 Section 53-0207.

Figure 34: Chart. Example distribution of layer thickness measurements along the section for the PATB layer for the SPS-1 Section 20-0112.

Figure 35: Chart. Example distribution of layer thickness measurements along the section for the PATB layer for the SPS-2 Section 08-0224.

Figure 36: Chart. Example distribution of layer thickness measurements along the section for the PCC surface layer for the SPS-2 Section 08-0215.

Figure 37: Chart. Example distribution of layer thickness measurements along the section for the PCC surface layer for the SPS-8 Section 39-0809.

Figure 38: Chart. Example distribution of layer thickness measurements along the section for the PCC surface layer for the SPS-7 Section 19-0706.

Figure 39: Chart. Example distribution of layer thickness measurements along the section for the surface and binder layer for the SPS-1 Section 55-0118.

Figure 40: Chart. Example distribution of layer thickness measurements along the section for the surface and binder layer for the SPS-8 Section 48-0802.

Figure 41: Chart. Example distribution of layer thickness measurements along the section for the surface layer for the SPS-5 Section 35-0507.

Figure 42: Chart. Example distribution of layer thickness measurements along the section for the surface layer for the SPS-6 Section 42-0603.

Figure 43: Chart. Example distribution of layer thickness measurements along the section for the AC binder course for the SPS-5 Section 24-0504.

Figure 44: Chart. Example distribution of layer thickness measurements along the section for the binder course for the SPS-6 Section 29-0607.

Figure 45: Equation. The null and alternative hypotheses for two-sided t-test.

Figure 46: Equation. The null and alternative hypothesis for one-sided t-test.

Figure 47: Chart. The Frequency distribution of mean thickness deviations for all four target thicknesses of the DGAB layer.

Figure 48: Chart. Frequency distribution of elevation and core thickness measurements deviations for DGATB with 102-mm (4-in) target thickness.

Figure 49: Chart. Frequency distribution of elevation and core thickness measurements deviations for DGATB with 203-mm (8-in) target thickness.

Figure 50: Chart. Frequency distribution of elevation and core thickness measurements deviations for DGATB with 305-mm (12-in) target thickness.

Figure 51: Chart. Frequency distribution of elevation and core thickness measurements deviations for LC with 152-mm (6-in) target thickness.

Figure 52: Chart. Frequency distribution of elevation and core thickness measurements deviations for PATB with 102-mm (4-in) target thickness.

Figure 53: Chart. Frequency distribution of elevation and core thickness measurements deviations for PCC with 76-mm (3-in) target thickness.

Figure 54: Chart. Frequency distribution of elevation and core thickness measurements deviations for PCC with 127-mm (5-in) target thickness.

Figure 55: Chart. Frequency distribution of elevation and core thickness measurements deviations for PCC with 203-mm (8-in) target thickness.

Figure 56: Chart. Frequency distribution of elevation and core thickness measurements deviations for PCC with 279-mm (11-in) target thickness.

Figure 57: Chart. Frequency distribution of elevation and core thickness measurements deviations for SB with 51-mm (2-in) target thickness.

Figure 58: Chart. Frequency distribution of elevation and core thickness measurements deviations for SB with 102-mm (4-in) target thickness.

Figure 59: Chart. Frequency distribution of elevation and core thickness measurements deviations for SB with 127-mm (5-in) target thickness.

Figure 60: Chart. Frequency distribution of elevation and core thickness measurements deviations for SB with 178-mm (7-in) target thickness.

Figure 61: Chart. Frequency distribution of elevation and core thickness measurements deviations for SB with 203-mm (8-in) target thickness.

Figure 62: Chart. Example of normally distributed thickness deviations (elevation data, LC, target thickness 152 mm [6 in]).

Figure 63: Chart. Example of a skewed distribution for layer thickness deviation (core data, PCC, target thickness 279 mm [11 in]).

Figure 64: Chart. Percentage distribution of the elevation measurements for a tolerance level of 6.35 mm (0.25 in) for different material types and design thicknesses.

Figure 65: Chart. Percentage distribution of the elevation measurements for a tolerance level of 12.7 mm (0.5 in) for different material types and design thicknesses.

Figure 66: Chart. Percentage distribution of the elevation measurements for a tolerance level of 25.4 mm (1 in) for different material types and design thicknesses.

Figure 67: Chart. Results of one-sided t-tests for the differences between mean elevation and design thicknesses for a tolerance level of 6.35 mm (0.25 in).

Figure 68: Chart. Results of one-sided t-tests for the differences between mean elevation and design thicknesses for a tolerance level of 12.7 mm (0.5 in).

Figure 69: Chart. Results of one-sided t-tests for the differences between mean elevation and design thicknesses for a tolerance level of 25.4 mm (1 in).

Figure 70: Chart. Percentage distribution of core measurements by layer type and design thickness for a tolerance level of 6.35 mm (0.25 in).

Figure 71: Chart. Percentage distribution of core measurements by layer type and design thickness for a tolerance level of 12.7 mm (0.5 in).

Figure 72: Chart. Percentage distribution of core measurements by layer type and design thickness for a tolerance level of 25.4 mm (1 in).

Figure 73: Chart. Results of one-sided t-tests for the differences between core measurements and design thicknesses for tolerance level of 6.35 mm (0.25 in).

Figure 74: Chart. Results of one-sided t-tests for the differences between mean core and design thicknesses by layer type and design thickness for tolerance level of 12.7 mm (0.5 in).

Figure 75: Chart. Results of one-sided t-tests for the differences between mean core and design thicknesses by layer type and design thickness for tolerance level of 25.4 mm (1 in).

Figure 76: Equation. Skewness definition.

Figure 77: Equation. Kurtosis definition.

Figure 78: Equation. Non-dimensional skewness coefficient definition.

Figure 79: Equation. Non-dimensional kurtosis coefficient definition.

Figure 80: Equation. Definition of statistic.

Figure 81: Equation. Definition of b2 statistic.

Figure 82: Equation. Definition of intermediate parameter A.

Figure 83: Equation. Definition of intermediate parameter B.

Figure 84: Equation. Definition of intermediate parameter C.

Figure 85: Equation. Definition of intermediate parameter D.

Figure 86: Equation. Definition of intermediate parameter E.

Figure 87: Equation. Definition of skewness test statistic z1.

Figure 88: Equation. Definition of the mean of intermediate parameter meanb2.

Figure 89: Equation. Definition of the variance of intermediate parameter varb2.

Figure 90: Equation. Definition of intermediate parameter F.

Figure 91: Equation. Definition of intermediate parameter G.

Figure 92: Equation. Definition of intermediate parameter H.

Figure 93: Equation. Definition of kurtosis test statistic z2.

Figure 94: Equation. Cumulative frequencies definition.

Figure 95: Equation. D-max statistic definition.

Figure 96: Equation. Critical value definition.

Figure 97: Equation. Kolmogorov-Smirnov test evaluation criteria.

Figure 98: Chart. Example of Kolmogorov-Smirnov normal distribution goodness-of-fit test (DGAB layer SPS-1 LTPP section 01_0101).

LIST OF ABBREVIATIONS

AC = Asphalt concrete (surface course).

AGG = Aggregate base (identical to dense-graded aggregate base).

AASHTO = American Association of State Highway and Transportation Officials.

ASTM = American Society for Testing and Materials.

ATB = Asphalt-treated base (dense-graded, generally similar to the AC surface course).

COV = Coefficient of variation.

CRCP = Continuously reinforced concrete pavement.

CTB = Cement-treated base.

DGAB = Dense-graded aggregate base (unbound).

DGATB = Dense-graded asphalt-treated base (bound).

FHWA = Federal Highway Administration.

GB = Granular base.

GPR = Ground Penetrating Radar.

GPS = General Pavement Studies.

HMAC = Hot-mix asphalt concrete.

JCP = Jointed concrete pavement.

JPCP = Jointed plain concrete pavement.

JRCP = Jointed reinforced concrete pavement.

LC = Lean concrete (base).

LTPP = Long Term Pavement Performance (program).

PCC = Portland cement concrete.

PATB = Permeable asphalt-treated base.

QA = Quality assurance.

QC = Quality control.

RSC = Regional Support Contractor.

SHRP = Strategic Highway Research Program.

SB = Surface and binder (layer).

SPS = Specific Pavement Studies.


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.
FHWA
United States Department of Transportation - Federal Highway Administration