Analysis Projects

Projects Related to Strategic Objective 1:
Traffic Characterization and Prediction

Project: Traffic Data Collection, Analysis, and Forecasting for Mechanistic Pavement Design ((National Cooperative Highway Research Program (NCHRP) 1-39)
Status: Completed
Objective: 1A
Objectives/Description of Work: To provide guidelines for collecting traffic data to use in pavement design and in software (TrafLoad) for analyzing traffic data and for producing the traffic data inputs required for mechanistic pavement analysis and design.
Outcome: NCHRP Reports 509 and 538.
Sponsor: NCHRP

Project: Optimization of Traffic Data Collection for Specific Pavement Applications
Status: Completed.
Objective: 1B
Objectives/Description of Work: To define the optimal traffic data collection and report efforts required to support sound conclusions in different pavement design and analysis applications.
Outcome: FHWA-HRT-05-079.
Sponsor: Federal Highway Administration (FHWA)

Project: Estimating Cumulative Traffic Loads, Phase 1
Status: Completed
Objective: 1C
Objectives/Description of Work: To develop and apply procedures to estimate cumulative traffic load spectra for each Long-Term Pavement Performance (LTPP) test site.
Outcome: Methodology for estimating traffic load spectra documented in report FHWA-RD-00-054. Estimates of historical load spectra for 12 LTPP test sites. Identification of anomalies in traffic data trends in the LTPP database.
Sponsor: FHWA

Project: Estimating Cumulative Traffic Loads, Phase 2
Status: Completed
Objective: 1C
Objectives/Description of Work: To assess the traffic axle load projection procedure developed in Phase 1, using all 890 LTPP traffic sites.
Outcome: Methodology for estimating traffic load spectra documented in report FHWA-RD-03-094. Axle load spectra projected for 558 (63 percent) of the 890 LTPP traffic sites are reasonable. The projections for the remaining 332 (37 percent) of traffic sites are unreliable. A Pavement Loading Guide was developed to overcome projection difficulties.
Sponsor: FHWA

Projects Related to Strategic Objective 2:
Materials Characterization

Project: Assessment of Selected LTPP Material Data Tables and Development of Representative Test Tables
Status: Completed
Objective: 2A
Objectives/Description of Work: Identify, and then provide the basis for resolving, any anomalous observations present in the LTPP laboratory materials data. Laboratory resilient modulus data will be addressed in separate studies.
Outcome: FHWA-RD-02-001. Issues addressed include the availability, characteristics, and quality of the data in the selected tables. Anomalies in the data were identified and corrected where possible, and the "cleaned-out" data were used in developing representative data tables.
Sponsor: FHWA

Project: Study of LTPP Laboratory Resilient Modulus Test Data and Response Characteristics
Status: Completed
Objective: 2A
Objectives/Description of Work: To review in detail the LTPP resilient modulus data of repeated-load resilient modulus tests on all unbound pavement materials and soils from the SPS and GPS test sections for both rigid and flexible pavements.
Outcome: FHWA-RD-02-051. A total of 2,014 resilient modulus tests of unbound pavement materials and soils have a level-E data status, while 1,594 tests have not yet obtained a level-E status in the LTPP database as of the October 2000 data release.
Sponsor: FHWA

Project: Temperature Predictions and Adjustment Factors for Asphalt Pavements
Status: Completed
Objective: 2B
Objectives/Description of Work: (1) Develop a model to predict the temperature within an asphalt layer from surface temperature data during falling- weight deflectometer (FWD) testing. (2) Develop models to adjust backcalculated asphalt moduli, pavement deflections, and deflection basin shape factors for temperature.
Outcome: FHWA-RD-98-085. Using 40 Seasonal Monitoring Program (SMP) sites, the following were created: (1) A model to predict asphalt layer temperature from routine deflection testing data; (2) Temperature adjustment models for backcalculated asphalt moduli, pavement deflections, and deflection basin shape factors.
Sponsor: FHWA

Project: Analyses Relating to Pavement Material Characterizations and Their Effects on Pavement Performance
Status: Completed
Objective: 2B
Objectives/Description of Work: To provide a combined procedure that can be used for pavement diagnostics and rehabilitation studies in support of the 1993 American Association of State Highway and Transportation Officials (AASHTO) Design Guide.
Outcome: FHWA-RD-97-076. This study details the procedures to backcalculate pavement layer moduli in support of the 1993 AASHTO Design Guide. The procedure recommended was based on a combination of the American Society for Testing and Materials (ASTM) D5858 and the procedure developed as a product from the Strategic Highway Research Program (SHRP).
Sponsor: FHWA

Project: Backcalculation of Layer Parameters for LTPP Test Sections, Volume I
Status: Completed
Objective: 2B
Objectives/Description of Work: Backcalculate the elastic layer properties for rigid pavements from FWD data, to use in further data analyses using elastic solid (ES) and dense-liquid (DL) approaches.
Outcome: FHWA-RD-00-086. This study documents the results of backcalculation of layer material properties from FWD data for all rigid pavement sections in the Specific Pavement Studies (SPS), General Pavement Studies (GPS), and Seasonal Monitoring Program (SMP) in the United States and Canada, using the slab on ES and DL foundation-based procedures.
Sponsor: FHWA

Project: Backcalculation of Layer Parameters for LTPP Test Sections, Volume II
Status: Completed
Objective: 2B
Objectives/Description of Work: (1) Backcalculate the elastic layer properties for rigid and flexible pavements from FWD data for use in further data analyses using ES and DL approaches. (2) Provide any modifications to the current guidelines.
Outcome: FHWA-RD-01-113. This study documents the results of backcalculation of layer material properties from FWD data for all rigid pavement sections in SPS, GPS, and SMP in the United States and Canada, using the slab on ES and DL foundation-based procedures.
Sponsor: FHWA

Project: Review of LTPP Backcalculation Results
Status: Completed
Objective: 2B
Objectives/Description of Work: (1) Improving the reliability of the backcalculated pavement layer parameters in the database. (2) Providing the basis for improved guidelines for review and evaluation of backcalculated results for both rigid and flexible pavements.
Outcome: FHWA-RD-00-086.
Sponsor: FHWA

Projects Related to Strategic Objective 3:
Determination of Environmental Effects in Pavement Design and Performance Prediction

Project: Environmental Effects in Pavement Mix and Structural Design Systems (NCHRP 9-23)
Status: Active
Objective: 3A
Objectives/Description of Work: (1) Validating the latest Integrated Climatic Model (ICM) developed in NCHRP 1-37A with the full LTPP SMP data. (2) Developing practical guidelines for selecting ICM input data sets. (3) Verifying the estimated rate of aging simulated by SuperpaveTM procedures.
Outcome: To be finalized.
Sponsor: NCHRP

Project: Daily and Seasonal Variations in In-Situ Material Properties (NCHRP 20-50(7/12))
Status: Active
Objective: 3A
Objectives/Description of Work: (1) Characterizing the patterns of daily and seasonal changes in in-situ pavement material properties. (2) Determining the relationships between those changes and causal factors for flexible and rigid pavements.
Outcome: Web Document 60. Information on seasonal variations in pavement material properties and structural capacity. Models that relate material parameters to the factors causing variations.
Sponsor: NCHRP

Project: Study of LTPP Pavement Temperatures
Status: Completed
Objective: 3A
Objectives/Description of Work: (1) To compare the pavement temperature data collected on the LTPP test sections, using manual probes, in-pavement thermistor probes, and infrared temperature sensors. (2) To characterize the variability in the measurements obtained with each type of device.
Outcome: FHWA-RD-02-071. Generated a report documenting the analysis approach and findings. Improved quality of LTPP pavement temperature data through identification and correction of errors.
Sponsor: FHWA

Project: Analysis of Time Domain Reflectometry (TDR) Data
Status: Completed
Objective: 3A
Objectives/Description of Work: (1) To generate estimates of gravimetric moisture contents at LTPP SMP sites through interpretation of TDR measurements. (2) To estimate the error associated with the TDR-based moisture content data.
Outcome: FHWA-RD-99-115. Computed volumetric and gravimetric moisture content data for the LTPP seasonal monitoring sites. Developed software (MOISTER) and algorithms to interpret TDR traces.
Sponsor: FHWA

Project: Seasonal Variations in Unbound Pavement Materials
Status: Completed
Objective: 3A
Objectives/Description of Work: (1) To evaluate the moisture prediction capabilities of the Enhanced ICM. (2) To characterize the variations in backcalculated pavement layer moduli under nonfrozen conditions. (3) To develop models to predict backcalculated layer moduli.
Outcome: Provided the basis for the development of the Enhanced ICM and the layer modulus backcalculation models that were used in the 2002 Pavement Design Guide.
Sponsor: FHWA

Project: Determination of Frost Penetration in LTPP Sections
Status: Completed
Objective: 3B
Objectives/Description of Work: To estimate of the probable frost locations within the pavement structure based upon interpretation of resistivity and temperature measurements at SMP test sections.
Outcome: FHWA-RD-99-088. Data that delineate the frozen zones within the pavement cross section, for the LTPP seasonal monitoring sites. An analysis procedure and software (FROST) developed to interpret data.
Sponsor: FHWA

Project: Effect on Performance of Multiple Freeze Cycles vs. Deep Frost Penetration
Status: Completed
Objective: 3B
Objectives/Description of Work: Quantifying the influence of seasonal frost penetration on the rate of loss of pavement performance for environments where deep, sustained frost penetration occurs and for environments where multiple, shallow freeze/thaw cycles occur.
Outcome: FHWA-HRT-06-121.
Sponsor: FHWA

Project: Verification of LTPP Virtual Weather Stations
Status: Completed
Objective: 3C
Objectives/Description of Work: Evaluate accuracy of climatic data derived from the National Climatic Data Center (NCDC) for LTPP GPS test sections.
Outcome: FHWA-RD-03-092.
Sponsor: FHWA

Project: LTPP Seasonal Asphalt Concrete Pavement Temperature Models
Status: Completed
Objective: 3E
Objectives/Description of Work: Verify the existing SHRP low pavement temperature models, and develop an improved model for Superpave binder selection.
Outcome: FHWA-RD-97-103. (1) Improved LTPP low pavement temperature model for SuperPave binder selection. (2) A new seasonal asphalt concrete (AC) database.
Sponsor: FHWA

Projects Related to Strategic Objective 4:
Evaluation and Use of Pavement Condition Data in Pavement Management

Project: Guide for Pavement Management (NCHRP 1-35A)
Status: Completed
Objective: 4A
Objectives/Description of Work: Develop a comprehensive guide for pavement management that documents the state of the practice and identifies state-of-the-art technologies and processes applicable to pavement management systems.
Outcome: AASHTO Pavement Management Guide
Sponsor: NCHRP

Project: Analysis of LTPP Friction Data
Status: Completed
Objective: 4A
Objectives/Description of Work: Evaluate the availability, characteristics, quality, and potential uses of the friction data being collected by highway agencies for the LTPP program.
Outcome: FHWA-RD-99-037. Findings documented the availability and variability of friction data being collected under the LTPP program.
Sponsor: FHWA

Project: Analysis of LTPP Friction Data
Status: Completed
Objective: 4A
Objectives/Description of Work: Evaluate the availability, characteristics, quality, and potential uses of the friction data being collected by highway agencies for the LTPP program.
Outcome: FHWA-RD-99-037: Findings document availability and variability of friction data being collected under the LTPP program.
Sponsor: FHWA

Project: Study of LTPP Distress Data Variability
Status: Completed
Objective: 4A
Objectives/Description of Work: Characterize the variability associated with distress data collected through manual and photographic distress surveys.
Outcome: FHWA-RD-99-074. Quantitative information on the variability of LTPP pavement distress data in terms of two collection approaches: manual and PASCO/PADIAS film derived.
Sponsor: FHWA

Project: Distress Data Consolidation
Status: Completed
Objective: 4A
Objectives/Description of Work: Produce a comprehensive consolidated distress data set to reconcile differences between data collected, using manual and automated (photographic PADIAS) approaches on 2,000 LTPP test sections including AC, jointed concrete (plain or reinforced), and CRCP.
Outcome: FHWA-RD-01-143. Generally, the distress survey results were found to be independent of the data collection methodology whether manual and automated (PADIAS 1.x and 4.2 software). Distress surveys using the manual or the automated method yielded similar results.
Sponsor: FHWA

Project: LTPP Profile Variability
Status: Completed
Objective: 4A
Objectives/Description of Work: Evaluate the quality and variability of the International Roughness Index (IRI) data in the LTPP database. All LTPP profiles collected on 2,062 test sections between June 1989 and October 1997 were visually reviewed.
Outcome: FHWA-RD-00-113. The leading cause of the LTPP Information Management System (IMS) profile run data problems is related to the equipment or the operator, such as the profilometer or its calibration.
Sponsor: FHWA

Project: Preliminary Evaluation and Analysis of LTPP Faulting Data
Status: Completed
Objective: 4A
Objectives/Description of Work: Evaluate the LTPP joint-faulting data to identify and explain anomalous data, and develop representative faulting indices and statistics for each jointed concrete pavements (JCP) test section.
Outcome: FHWA-RD-00-076. A summary of statistics characterizing joint faulting. Recommendations for improving future faulting data collection, specifically with respect to the necessity for improving the precision of faulting measurements.
Sponsor: FHWA

Project: Characterization of Transverse Profiles
Status: Completed
Objective: 4A
Objectives/Description of Work: Evaluate the LTPP transverse profile data to (1) quantify bias and precision and (2) develop and compute summary parameters (rut indices) to characterize pavement rutting.
Outcome: FHWA-RD-01-024. Computed transverse profile indices (rut statistics) added to the database. Estimated bias and precision. Recommended improvements and adjustments in transverse profile monitoring. Provided information on limitations of three-point and five-point rut depths.
Sponsor: FHWA

Project: Pavement Smoothness Index Relationships
Status: Completed
Objective: 4A
Objectives/Description of Work: Develop smoothness index relationships between IRI and PI (PI 5-millimeter (mm), PI 2.5-mm, and PI 0.0) that can assist States in transitioning to an IRI or PI 0.0 smoothness specification for HMA and portland cement concrete (PCC) pavements, using LTPP profile data.
Outcome: FHWA-RD-02-057. 54 models were formulated to assist State agencies in transitioning smoothness specification limits from PI (5-mm, 2.5-mm, and 0-mm) to IRI or to PI0.0
Sponsor: FHWA

Project: Smoothness Index Differences Related to LTPP Equipment Type
Status: Completed
Objective: 4A
Objectives/Description of Work: Characterize the differences in pavement profile indices that may be attributed to differences in the devices used to obtain longitudinal profile data.
Outcome: FHWA-HRT-05-054.
Sponsor: FHWA

Project: Study of LTPP Pavement Deflections
Status: Completed
Objective: 4B
Objectives/Description of Work: Assess and characterize the variability in FWD deflection data. Evaluate FWD test patterns and drop sequences. Identify data discrepancies that need to be resolved.
Outcome: FHWA-RD-03-093.
Sponsor: FHWA

Project: Feasibility of Using FWD Deflection Data to Characterize Pavement Construction Quality (NCHRP 20-50(9))
Status: Completed
Objective: 4D
Objectives/Description of Work: Evaluate the feasibility of using FWD data as a quality control and quality assurance (QC/QA) measure during the construction of pavement structures.
Outcome: Web Document 52. In general, FWD test results provided data that can be used with confidence to estimate material properties (mainly stiffness or moduli) and their variations at each layer interface during new or reconstructed pavement construction.
Sponsor: NCHRP

Projects Related to Strategic Objective 5:
Development of Pavement Response and Performance Models Applicable to Pavement Design and Performance Prediction

Project: Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures (Phase II) (NCHRP 1-37A)
Status: Completed
Objective: 5A
Objectives/Description of Work: Develop and deliver the 2002 Guide for Design of New and Rehabilitated Pavement Structures, based on mechanistic-empirical principles, accompanied by the necessary computational software, for adoption and distribution by AASHTO.
Outcome: The 2002 Pavement Design Guide
Sponsor: NCHRP

Project: Comparison and Quality Evaluation of LTPP Dynamic Load Response Data from Ohio and North Carolina
Status: Project completed with report pending.
Objective: 5A
Objectives/Description of Work: Determine the approaches and methodologies most appropriate for applications of measured stress, strain, and deflection response obtained from in-service roads, to theoretical (mechanistic) analysis concepts and design processes.
Outcome: Corrections of Ohio and North Carolina IMS dynamic load response data.
Sponsor: FHWA

Project: Variations in Pavement Design Inputs (NCHRP 20-50(5))
Status: Completed
Objective: 5B
Objectives/Description of Work: Define the variability of the most important pavement (both PCC and AC) design parameters (e.g., layer thickness and modulus, concrete strength, load transfer efficiency, etc.)
Outcome: Web Document 48. Identifies key parameters and recommends variabilities for those parameters, to help pavement engineers to achieve design reliability for a pavement.
Sponsor: NCHRP

Project: Validation of Guidelines for k-Value Selection and Concrete Pavement Performance Prediction
Status: Completed
Objective: 5C
Objectives/Description of Work: Apply the LTPP data to test and verify the improved pavement support guidelines and AASHTO performance model proposed in NCHRP 1-30. Evaluate and analyze PCC pavements to develop recommendations for long-lived concrete pavements.
Outcome: FHWA-RD-96-198 Better estimates of subgrade elastic k-value (modulus of subgrade reaction) through improved correlations with soil properties and tests, improved backcalculation procedures and slab size adjustments, and consideration of bedrock and embankments.
Sponsor: FHWA

Project: Design and Construction of PCC Pavements, Volumes I, II, and III
Status: Completed
Objective: 5C
Objectives/Description of Work: (1) Determine the design and construction features that will influence long- term performance, using the LTPP PCC data. (2) Develop improved PCC performance prediction models. (3) Develop recommendations for improving the design and construction of PCC pavements.
Outcome: FHWA-RD-98-052; FHWA-RD-98-127; FHWA-RD-98-113. Develops recommendations and performance prediction models for key features of PCC pavements: (1) transverse joint faulting and spalling, (2) transverse cracking and corner breaks, and (3) roughness.
Sponsor: FHWA

Projects Related to Strategic Objective 6: Maintenance and Rehabilitation Strategy Selection and Performance Prediction

Project: Effectiveness of Maintenance and Rehabilitation Options (NCHRP 20-50(3/4))
Status: Completed
Objective: 6A
Objectives/Description of Work: Assess the relative performance of different pavement maintenance and rehabilitation treatments on treatment effectiveness, using the data drawn from the SPS-3, SPS-5, GPS-6B, SPS-6, and GPS-7B.
Outcome: Web Document 47. Effective maintenance and rehabilitation treatments are identified and evaluated for flexible and rigid pavements, respectively.
Sponsor: NCHRP

Project: Performance of Rehabilitated Asphalt Concrete Pavements in the LTPP Experiments—Data Collected Through February 1997
Status: Completed
Objective: 6A
Objectives/Description of Work: Summarize the initial observations of the 125 Summarize the initial observations of the 17 SPS-5 (Study of Rehabilitation of AC Pavements) projects and the 125 GPS-6 (AC Overlay on AC Pavements) test sections as of February 1997.
Outcome: FHWA-RD-00-029.
Sponsor: FHWA

Project: Assessment of the SPS-7 Bonded Concrete Overlays Experiment
Status: Completed
Objective: 6A
Objectives/Description of Work: Review the SPS-7 bonded concrete overlay projects and data to identify data deficiencies and construction deviations, and assess the analytical potential of the SPS-7 experiment and projects.
Outcome: FHWA-RD-98-130. Findings and recommendations regarding the SPS-7 experiment: the conclusion was that the results of the SPS-7 experiment were of marginal value at best.
Sponsor: FHWA

Project: LTPP Maintenance and Rehabilitation Data Review
Status: Completed
Objective: 6A
Objectives/Description of Work: Provide a detailed review of the maintenance and rehabilitation (M&R) data collected on all test sections included in the LTPP program.
Outcome: FHWA-RD-01-019. 757 test sections have undergone some type of M&R activity. Among these test sections, only 23 anomalies were found. These anomalies consist primarily of sections that have patching that has been recorded in the M&R tables, but where there are no corresponding increases in patching.
Sponsor: FHWA

Project: Guide on Pavement Rehabilitation Strategies (NCHRP 1-38)
Status: Completed
Objective: 6B
Objectives/Description of Work: Develop a process for the selection of appropriate rehabilitation strategies for the ranges of pavement types and conditions found in the United States.
Outcome: Web Document 35. A process to address various aspects of data collection, pavement evaluation, selection of rehabilitation techniques, formation of alternative rehabilitation strategies, life-cycle cost analysis, and selection of a preferred rehabilitation strategy.
Sponsor: NCHRP

Project: Guide for Optimal Timing of Pavement Preventive Maintenance Treatment Applications (NCHRP 14-14)
Status: Completed
Objective: 6B
Objectives/Description of Work: Develop a methodology for determining the optimal timing for the application of preventive maintenance treatments to flexible and rigid pavements.
Outcome: Report 523. Develop a methodology for determining the optimal timing for the application of preventive maintenance treatments to flexible and rigid pavements.
Sponsor: NCHRP

Projects Related to Strategic Objective 7:
Quantification of the Performance Impact of Specific Design Features

Project: Relative Performance of Jointed Plain Concrete Pavement (JPCP) with Sealed and Unsealed Joints (NCHRP 20-50(2))
Status: Completed
Objective: 7A
Objectives/Description of Work: Compare the performance of JPCPs that have been designed and constructed with unsealed joints to the performance of JPCPs with sealed joints, using just five LTPP sites suitable for this analysis: the SPS-4 supplemental test sites in Arizona, Colorado, and Utah.
Outcome: Web Document 32. This study does not conclude that unsealed joints are any more likely to develop joint spalling than sealed joints. The narrow unsealed-joint test sections do, in general, exhibit more faulting and higher rates of IRI increase than most other sections.
Sponsor: NCHRP

Project: Structural Factors for Flexible Pavements—Initial Evaluation of the SPS-1 Experiment
Status: Completed
Objective: 7A
Objectives/Description of Work: Determine the effectiveness of HMA design features such as structural factors (including asphalt concrete thickness, base type, base thickness, and drainage) and site conditions (traffic, subgrade type, and climatic factors).
Outcome: FHWA-RD-01-166. As of January 2000, 18 SPS-1 projects (11 projects built over fine-grained soils and 7 built over coarse-grained soils) have been constructed, for a total of 248 test sections. This study documents the first comprehensive review and evaluation.
Sponsor: FHWA

Project: Structural Factors of Jointed Plain Concrete Pavements: SPS-2—Initial Evaluation and Analysis
Status: Completed
Objective: 7A
Objectives/Description of Work: Determine the long-term effectiveness of design features (including slab thickness, PCC flexural strength, base type and drainage, and slab width) and site conditions (including traffic, subgrade type, and climate) on doweled JPCP performance.
Outcome: FHWA-RD-01-167. As of January 2000, 13 SPS-2 projects had been constructed and an additional site in California had been nominated for construction. These 14 projects filled in 11 (69 percent) of the 16 SPS-2 factorial cells.
Sponsor: FHWA

Project: Rehabilitation of Asphalt Concrete Pavements—Initial Evaluation of the SPS-5 Experiment
Status: Completed
Objective: 7A
Objectives/Description of Work: Summarize the initial observations of the 18 SPS-5 (Study of Rehabilitation of AC Pavements) projects (without the 125 GPS-6 (AC Overlay on AC Pavements) test sections) as of January 2000.
Outcome: FHWA-HRT-01-168.
Sponsor: FHWA

Project: Rehabilitation of Jointed PCC Pavements: SPS-6—Initial Evaluation and Analysis
Status: Completed
Objective: 7A
Objectives/Description of Work: Assess the effects of climatic regions, type of concrete pavements (plain or reinforced), and existing pavement conditions prior to rehabilitation (fair or poor) incorporating different methods of rehabilitation with or without asphalt concrete overlays.
Outcome: FHWA-RD-01-169.
Sponsor: FHWA

Project: Evaluation and Analysis of LTPP Pavement Layer Thickness Data
Status: Completed
Objective: 7A
Objectives/Description of Work: Assess the quality and completeness of pavement layer thickness using levels A to E data, and provide recommendations for improving the data in the LTPP database.
Outcome: FHWA-RD-03-041. Analysis of data completeness at level E revealed 3,457 pavement layer structures in the EXPERIMENT_ SECTION table. Some 3,229 (93 percent) of these structures have records in table TST_L05A, while 3,240 (94 percent) have records in table TST_L05B.
Sponsor: FHWA

Project: Study of Environmental Effects in the Absence of Heavy Loads: SPS-8—Initial Evaluation and Analysis
Status: Completed
Objective: 7A
Objectives/Description of Work: Examine the effect of climatic factors and subgrade soil types on pavement sections that incorporate different asphalt and concrete thickness designs and that are subjected to very limited traffic.
Outcome: As of June 2001, a total of 20 SPS-8 sites with 48 regular sections (32 flexible and 16 rigid) were constructed, filling in 16 of the 24 experimental cells. This leaves eight of the desired cells (subgrade and climate) with no experimental data.
Sponsor: FHWA

Project: Evaluation of Joint and Crack Load Transfer
Status: Completed
Objective: 7A
Objectives/Description of Work: Present an initial evaluation of the deflection data collected under the LTPP program related to load transfer efficiency (LTE). Representative LTE indexes and joint stiffnesses were calculated for all GPS, SPS, and SMP rigid test sections.
Outcome: FHWA-RD-02-088. Testing times and seasons were found to have profound effects on LTE. For the same joints, LTEs measured early in the morning in a cool season were found to be much lower than LTEs measured in the afternoon in warmer weather.
Sponsor: FHWA

Project: Influence of Design and Construction Features on the Response and Performance of New Flexible and Rigid Pavements (NCHRP 20-50(10/16))
Status: Completed
Objective: 7A
Objectives/Description of Work: (1) Determine, for specific site conditions, the influences of design and construction features on pavement response. (2) Determine the contributions of design and construction features to achieving different levels of performance.
Outcome: Web Document 74. The LTPP data were analyzed to enhance understanding of the influences of the design and construction features on pavement response (as measured by deflection and strain) and performance (as measured by type and extent of distress or smoothness). The analytical investigations were performed to identify relationships between design and construction features, site factors, and performance.
Sponsor: NCHRP

Project: Contributions of Pavement Structural Layers to Rutting of Flexible Pavements (NCHRP 1-34A)
Status: Completed
Objective: 7B
Objectives/Description of Work: (1) Investigate whether the relative contributions of the layers to rutting in a flexible pavement can be determined from its transverse surface profile. (2) Prepare a method for estimating the relative contributions of pavement layers to total rutting.
Outcome: Report 468. (1) Confirmed that the relative contributions of layers to rutting in a flexible pavement can be determined from the pavement’s transverse surface profile. (2) Developed failure criteria predicting layer failure from a pavement’s transverse surface profile.
Sponsor: NCHRP

Project: Effectiveness of Subsurface Drainage for HMA and PCC Pavements (NCHRP 1-34B)
Status: Completed
Objective: 7B
Objectives/Description of Work: (1) Review the final report and supporting information developed in Project 1-34. (2) Develop an experimental plan to evaluate and test key findings from that report.
Outcome: Research Digest 268. (1) In SPS-1, HMA sections built on permeable bases without edgedrains perform better than those with edge drains. (2) In SPS-2, for JCP with dowels, both permeable bases and edgedrains were not found to significantly reduce joint faulting.
Sponsor: NCHRP

Project: Effects of Subsurface Drainage on Performance of Asphalt and Concrete Pavements (NCHRP 1-34C)
Status: Completed
Objective: 7B
Objectives/Description of Work: (1) Assess the feasibility of using the SPS-1 and SPS-2 data. (2) Develop a plan for analysis of the SPS-1 and SPS-2 data to quantify the effects of subsurface drainage on pavement performance.
Outcome: Report 499. (1) In SPS-1, for IRI and cracking, rated from poor to good: undrained DGAB, drained permeable asphalt-treated bases (PATB), and undrained DGATB, using 7-year data. (2) In SPS-2, for IRI and cracking, sections with undrained DGAB tend to do more poorly than those with PATB, using 7-year data.
Sponsor: NCHRP

Project: Effects of Subsurface Drainage on Performance of Asphalt and Concrete Pavements, Evaluation and Analysis of LTPP SPS-1 and SPS-2 Field Sections (NCHRP 1-34D)
Status: Completed
Objective: 7B
Objectives/Description of Work: (1) Test the functionality of the subsurface drainage features in SPS-1 and SPS-2. (2) Refine the relationships between subsurface drainage features and pavement performance developed in Projects 1-34 and 1-34C.
Outcome: (NCHRP 1-34D).
Sponsor: NCHRP

Project: Factors Affecting Pavement Smoothness (NCHRP 20-50(8/13))
Status: Completed
Objective: 7B
Objectives/Description of Work: Use the LTPP data to determine the effect of factors (e.g., pavement structure, rehabilitation techniques, climatic conditions, traffic levels, etc.) affecting pavement smoothness, and quantify the contribution of these factors to pavement smoothness.
Outcome: Web Document 40. Factors such as pavement structure, rehabilitation techniques, climatic conditions, traffic levels, layer materials and properties, and pavement distress affecting the smoothness of SPS-1, -2, -5, and -6 and GPS-1, -2, -3, -4, -5, -6, and -7 are investigated.
Sponsor: NCHRP

Project: Investigation of Development of Pavement Roughness
Objective: 7B
Objectives/Description of Work: Study the change in roughness at the SPS and GPS test sections, using the profile data.
Outcome: FHWA-RD-97-147. (1) Investigation of roughness characteristics of AC and PCC pavements in SPS and GPS experiments. (2) Development of models to predict changes in roughness. (3) Recommendations for quality assurance and profiling frequency for the test sections.
Sponsor: FHWA

Project: Common Characteristics of Good and Poorly Performing PCC Pavements
Objective: 7B
Objectives/Description of Work: Identify the site conditions and design/construction features of rigid pavements, which lead to good performance, and identify those conditions and features that lead to poor performance, using the LTPP data.
Outcome: FHWA-RD-97-131. Information regarding the design features and service conditions associated with rigid pavements that perform well, and those that do not perform as well.
Sponsor: FHWA

Project: Common Characteristics of Good and Poorly Performing AC Pavements
Objective: 7B
Objectives/Description of Work: Identify the site conditions and design/construction features of flexible pavements, which lead to good performance, and identify those conditions and features that lead to poor performance, using the LTPP data.
Outcome: FHWA-RD-99-193. Information regarding the design features and service conditions associated with flexible pavements that perform well, and those that do not perform as well.
Sponsor: FHWA