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.

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.

^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.