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Publication Number: FHWA-HRT-06-066
Date: March 2006

Long-Term Pavement Performance Inventory Data Collection Guide

Chapter 1. Introduction

Many different types of data are collected on test sections studies as part of the Long-Term Pavement Performance (LTPP) program. This document provides the guidelines necessary for collecting inventory data on these sections. Inventory data include those necessary to: 1) identify the test section, 2) describe the geometric details of its construction and the material properties of its structural constituents, and 3) identify construction costs and costs of subsequent maintenance and repair before the long-term monitoring (LTM) effort. Table 1 provides a general list of inventory data elements.

All of these data, with the exception of certain material properties such as subgrade strength and moisture content that change over time or environment, should remain constant throughout the monitoring period of each test section or project unless the pavement is resurfaced or rehabilitated during the period. In either case, the test section becomes for practical purposes a new pavement structure with new surface conditions, so the basic inventory data must be revised to describe these new conditions, while the original data is retained for reference in long-term cost analyses and studies of the effects of rehabilitation on deterioration rates. The additional rehabilitation data elements recommended for collection in the event this occurs during the monitoring period are discussed in the Maintenance and Rehabilitation Data Collection Guide.

This document provides data sheets and instructions to collect inventory data for the LTPP program. The inventory data sheets appear in numerical sequence at the end of this document.

The inventory data sheets have been taken from the original Long-Term Monitoring Data Collection Guide and modified to reflect evolution in planning for LTM of pavements. This was done partially to maintain some consistency with the LTM pilot study databases, but primarily to take advantage of the work already accomplished for the Federal Highway Administration (FHWA) during the LTM studies, and during studies for the National Cooperative Highway Research Program (NCHRP) Project 1-19.

The data sheets allow collection of detailed information on the variability of materials and layer thicknesses, because this variability is known to contribute heavily to pavement deterioration. Replicate test data is often unavailable, so single test results in these cases should be entered as the mean and other values left blank. However, whenever possible, data on variability should be obtained.

Data collected for a General Pavement Studies (GPS) test section should pertain to the original construction of the section or the most recent rehabilitation/reconstruction. The data sheets required for each GPS test section will depend on the type of materials contained in the structure of that test section. Sheets 1, 2, 3, and 4 are required for every GPS test section. Sheet 3 indicates the numbers of the additional required data sheets for each material type present in the pavement structure. Sheet 1A is required for every GPS test section where measurements are made with a global positioning system receiver.


Table 1. Items of Inventory Data To Be Collected
1. Test Section Identification

Route Number
State, County, and District
Lane Monitored
Experiment Code

Functional Class
Location of Test Section
Direction of Travel

2. Geometric Details and General Information

Number of Lanes
Lane Width
Type of Pavement
Type of Subsurface Drainage
Location of Subsurface Drains
Identification of Layer Materials
Thickness of Layers
Depth to Rigid Layer
Year Widened
Identification of Materials Used in Overlay or Reconstruction
Dowel Bar Diameter, Length, and Installation Method

Shoulder Width
Shoulder Structure
Portland Cement Concrete (PCC) Shoulder Joint Information
Year Originally Constructed
Thicknesses of Overlays or Final Layer
Years when Major Improvements Occurred
Joint Spacing, Reservoir Width
Sealant Type and Forming Method
Type of Load Transfer (Aggregate Interlock or Dowels)
Tie Bar Spacing, Coating, Diameter, Length, and Spacing

3. Material Properties
a. Subgrade Soil

Soil Type and Classification
Plasticity Index
In Situ Dry Density
In Situ Moisture Content
Swell Potential
Frost Susceptibility
Resilient Modulus
Relative Density
Optimum Laboratory Moisture Content

Liquid Limit
Percent Passing No. 40 Sieve
Percent Passing No. 200 Sieve
California Bearing Ratio
Modulus of Reaction
Maximum Laboratory Dry Density
Soil Suction
Rate of Heave

b. Base and Subbase Layers (Unbound or Stabilized)

Soil Type and Classification
Optimum Laboratory Moisture Content
Material Gradation
Percent of Stabilizing Agent
California Bearing Ratio
Resistance (R-Value)
Compressive Strength

Maximum Laboratory Dry Density
In Situ Dry Density
In Situ Moisture Content
Resilient Modulus
Type of Treatment (Cement, Lime, etc.)
Modulus of Subgrade Reaction

Asphalt Grade
Asphalt Content
Penetration of Original Asphalt
Source and Specific Gravity of Asphalt
Viscosity and Ductility of Original Asphalt
Softening Point of Asphalt
Types of Asphalt Modifiers
Original Stability
Properties of Laboratory Aged Asphalt
Type of Asphalt Plant
In-Place Mixture Properties
Type and Amount of Antistripping Additives
Compaction Data
Mixing Temperatures

Initial Air Voids
Voids in Mineral Aggregate
Types of Coarse and Fine Aggregates
Geologic Classifications of Coarse Aggregates
Polish Value of Coarse Aggregates
Gradations of Coarse and Fine Aggregates
Bulk Specific Gravities of Aggregates
Effective Specific Gravities of Aggregates
Aggregate Durability
Resilient Modulus
Tensile Strength
Creep Compliance
Moisture Susceptibility

d. Portland Cement Concrete Layers
Type, Amount, Yield Strength, and Placement of Reinforcing Steel
Mix Design Information
Coarse Aggregate Type and Gradation
Fine Aggregate Type and Gradation
Alkali Content of Cement
Entrained Air
Aggregate Durability
Method for Curing and Finishing

Modulus of Rupture
Elastic Modulus
Tensile Strength
Compressive Strength
Type of Paver
Type of Cement
Insoluble Residue
Bulk Specific Gravities

4. Historical Pavement Related Cost Data
Initial Construction Cost
Costs for Major Improvements
Maintenance Costs

Data collected for Specific Pavement Studies (SPS) experiment projects may be provided by an adjacent GPS test section. An entry must be available in the SPS_GPS_LINK table in the LTPP Information Management System (IMS) identifying the adjacent GPS test section number for the relevant project. Data for all SPS projects should pertain to the original construction before any construction related to the SPS requirements. Table 2 shows the data sheets required for each SPS experiment, by experiment number.


Table 2. Data Sheets Required by SPS Experiment
Inventory Data Sheets SPS Experiment Number
1 2 3A 4A 5 6 7 8 9B
1 - - X X X X X - X
2 - - X X X X X - X
3 - - X X X X X - X
4 - - X X X X X - X
5 - - - X - X X - X
6 - - - X - X X - X
7 - - - X - X X - X
8 - - - X - X X - X
9 - - - X - X X - X
10 - - - X - X X - X
11 - - - X - X X - X
12 - - X - X - X - X
13 - - X - X - X - X
14 - - X - X - X - X
15 - - X - X - X - X
16 - - X - X - X - X
17 - - X - X - X - X
18 - - X - X - X - X
19 - - X X X X X - X
20 - - X X X X X - X
21 - - X X X X X - X
22 - - X X X X X - X
23 - - X X X X X - X

A Data for SPS-3 and SPS-4 projects may be completed for an adjacent GPS test section. An entry must be available in the SPS_GPS_LINK table identifying the adjacent GPS test section number for the relevant SPS-3 or SPS-4 project.

B Inventory sheets for SPS-9 required only for overlay of existing pavements, with the exception of data sheet 1A.

C Inventory data sheet 1A is required for every SPS project or GPS test section where measurements are made with a global positioning system.


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