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Publication Number: FHWA-HRT-08-056
Date: November 2008

LTPP Manual for Profile Measurements and Processing

CHAPTER 1. INTRODUCTION

1.1 OVERVIEW OF THE LTPP PROGRAM

The Strategic Highway Research Program (SHRP) was a five-year research program that had a budget of $150 million and began in 1987. The research areas targeted under SHRP were asphalt concrete (AC), pavement performance, portland cement concrete (PCC) and structures, and highway operations. SHRP's Long Term Pavement Performance (LTPP) program was the first ever effort to study pavement performance in different climates and soil conditions at nearly 2,500 in-service pavement sections in all 50 States of the United States and in participating provinces in Canada. The LTPP program was designed as a 20-year study. The first five years of this program from 1987 to 1992 were administrated by SHRP, and since 1992, this program has been administrated by the FHWA.

For purposes of pavement data collection and coordination, the United States and participating Canadian provinces have been subdivided into four regions—North Atlantic, North Central, Southern, and Western—each served by a Regional Support Contractor (RSC). The boundaries defining the jurisdiction of each RSC are shown in figure 1

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Figure 1. Map. LTPP regions.

1.2 SIGNIFICANCE OF PAVEMENT PROFILE MEASUREMENTS

The longitudinal profile along the wheel paths in a pavement can be used to evaluate the roughness of the pavement by computing a roughness index such as the IRI. The change in longitudinal pavement profile over time, which is directly related to the change in roughness with time, is an important indicator of pavement performance. Hence, one aspect of the LTPP program is to collect pavement profile data at in-service pavement sections for use in many applications such as improving the prediction of pavement performance.

1.3 PROFILE DATA COLLECTION

The primary method used to obtain pavement profile measurements for the LTPP program is to profile test sections using a road profiler. Each RSC operates a profiler to collect data within its region. From the inception of the LTPP program until the end of 1996, profile data at test sections were collected using a model DNC 690 inertial profiler manufactured by K. J. Law Engineers, Inc. In late 1996, each RSC replaced their model K.J. Law DNC 690 profiler with a Model T-6600 inertial profiler manufactured by K. J. Law Engineers, Inc. In September 2002, each RSC replaced their K. J. Law T-6600 profiler with an ICC MDR 4086L3 inertial profiler. The operation and maintenance of the profiler and storage of collected data are the responsibility of each RSC.

When a profiler is not available, LTPP has elected to use the Dipstick®, which is a hand operated digital profiler manufactured by Face Company, as a backup device to collect longitudinal profile data. The Dipstick® is also used also to obtain transverse profile data at most sites. The North Atlantic, North Central, and Western RSCs are in possession of three Dipsticks®, while the Southern RSC has two Dipsticks®. A rod and level can be used to measure pavement profiles if a profiler or a Dipstick® is not available, or where other special circumstance or requirements rule out the profiler or the Dipstick®. However, this method is very labor intensive and is not typically used within the LTPP program.

1.4 OVERVIEW OF THE MANUAL

This manual describes procedures to be followed when measuring pavement profiles for the LTPP program using the ICC road profiler, the Dipstick®, and the rod and level. Procedures for calibration of equipment, data collection, record keeping, and maintenance of equipment for each of the profiling devices are described in this manual. This manual also describes procedures to be followed in the office when processing profile data collected in the field as well as guidelines on performing interregional comparison tests among the four LTPP profilers.

This document addresses those aspects of profile measurements that are relatively unique to the LTPP program. Other references (see references 1 to 14) should be consulted for general information.

 

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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.
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