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Publication Number: FHWA-RD-06-067
Date: March 2006

Guidelines for The Collection of Long-Term Pavement Performance Data

Chapter 6. Monitoring Data

6.1 Introduction

Monitoring data are collected on a periodic basis throughout the life of the test section as a means of tracking the structural and functional condition of the pavement sections over time. These collection activities provide a historical database that helps establish relationships among distress, performance, traffic and axle loads, age, maintenance, and other significant variables.

Monitoring data collected on LTPP sections include deflection measurements, surface friction measurements, surface distress evaluations, and longitudinal profile measurements. Each of these elements is governed by a different collection manual.

A general set of guides for the collection of the monitoring data is provided by chapter 3 of the original version of the DCG. This chapter also provides instructions for completing some of the data forms for monitored data. The versions of the DCG providing information for monitored data collection are as follows. The revision dates listed as part of the reference provide the timeframe during which each version of the document was relevant for the collection of monitoring data and the point at which the previous version was no longer relevant.

Each of the specific areas of data collection along with the appropriate references are discussed in the following sections.

6.2 Deflection Data

6.2.1 Introduction to Deflection Data

Deflection data are collected using FHWA-owned falling weight deflectometers (FWD) for the purpose of evaluating the pavement section structural condition. The field data collection software provided with the FWDs allows for thorough identification of the test data and for automatic collection of time, air and pavement temperature, location, deflections, load, and selected load and deflection time history data. In addition to the collected data, data that provide information about the calibration of each FWD are stored.

6.2.2 References Used in Collection of Deflection Data

Collection of FWD Data

Any LTPP FWD data collection activity conducted for inclusion in the IMS must be performed in strict accordance with the appropriate FWD manual as referenced below.

This manual was in use from January 1989 until the release of Version 2.0 in May 1993. In April 1992, a series of documents was released that addressed data collection on the projects associated with the various SPS experiments.

The 1993 version of the manual replaced the previous version from January 1989 and incorporated not only the various elements provided by the FWD directives between January 1989 and May 1993, but also the various SPS experiment documents.

Table 1 shows the timeline of the release of the FWD manuals; these detail how the deflection data should be collected for the LTPP program.

Table 1. Timeline of FWD Testing Manual Releases

1988 FWD Manual Version 1.0 released January 1988  
1989
1990
1991
1992
SPS Guidelines for FWD Testing released April 1992
1993
FWD Manual Version 2.0 released May 1993 SPS Guidelines were combined into FWD Manual and no longer required after May 1993.
1994
1995
1996
1997  
1998  
1999  
2000 FWD Manual Version 3.0 released January 2000  
FWD Manual Version 3.1 released October 2000
2001  
2002  
2003  
2004  
2005  
FWD Manual Version 4.0 released April 2005
2006  
2007  

Software Used in Processing Deflection Data

Other FWD documentation provides instruction for using software to perform quality control checks on the data before entry into the IMS. Specifically, FWDSCAN provides an initial review of the data before its being loaded into the database. This program also prepares the files for loading into the IMS. FWDCheck provides additional review of data; its use has been optional for much of the LTPP program. FWDConvert creates the standard FWD PDDX files from the database files created during data collection and incorporates the additional data elements required by LTPP. The final document provides information for using the FWD data collection program to obtain the FWD data required for the LTPP program.

6.3 Distress Data

6.3.1 Introduction to Distress Data Collection

Distress data for the LTPP program include information about type, severity, and amount of cracking on the test section; and about surface defects, transverse profile, faulting, patching, and other miscellaneous types of distress. Distress data for LTPP are collected using both semiautomated photographic equipment and manual methods. The methodologies used in collecting these data attempt to provide uniformity not only within each survey method, but also between the two survey methods.

6.3.2 References for All Distress Data Collection

The information contained in the IMS is intended to be common to both the automated and manual data collection methods. All pavement distress monitoring is performed using the Distress Identification Manual as referenced below. The manual contains definitions, severity level descriptions, and measurement methods for the pavement distresses identified for inclusion in the LTPP monitoring.

A draft version of the revised manual was released to the RSCs in April 2002 for use in collecting distress data. The revised manual was officially released for publication in October 2003.

6.3.3 References Specific to Manual Distress Data Collection

At the time of the manual surveys, the surveyor also collects transverse profile data on asphalt surfaced pavements and joint faulting on portland cement concrete (PCC) surfaced pavements. The following guidelines provide instruction on how these data are to be collected. They were incorporated into the 1993 version of the Distress Identification Manual. Additional information specific to the collection of transverse profile data also can be found in the field guidelines used in the collection of longitudinal profile data as referenced under section 6.4.2.

Table 2 provides a timeline for the use of all of the guides on manual distress data collection.

6.3.3 References Specific to Semiautomated Distress Data Collection

Semiautomated distress data collection involves the collection of 35-mm photographic images of the pavement surface and images for determining the transverse profile of the pavement surface. The collection of these images and analysis/interpretation of the transverse profile are governed by the following reference.

The methodology used for interpreting the distresses observed on the pavement surface from these images is provided by the following reference. In addition to this document, the interpretation procedure also uses the distress and severity level definitions provided by the Distress Identification Manual as previously referenced.

6.4 Longitudinal Profile Measurement

6.4.1 Introduction to Profile Measurement

Longitudinal profile data is collected for LTPP to provide information about the ride quality of the pavement surface. The primary means of collecting longitudinal profile data for LTPP has been through the use of vehicle-based longitudinal profilers. Over the years of the LTPP program, three sets of profilers have been used by each of the RSCs to collect these data. Procedures for collecting longitudinal profile data are referenced below. Each of the documents addresses collection of the data not only with the inertial profiler, but also with the FACEÒ Dipstick, which is used when collection with the inertial profiler is not feasible.

Table 2. Timeline of Revision to Distress Data Collection Procedures

1988      
1989
Distress Identification Manual released June 1989
1990
Revised Distress Identification Manual released October 1990
1991 Dipstick Manual released January 1991
Faultmeter Manual released June 1991
1992
1993
Revised Distress Identification Manual released May 1993 incorporated Dipstick and Faultmeter Manuals Dipstick Manual combined with Distress Identification Manual in May 1993 Faultmeter Manual combined with Distress Identification Manual in May 1993 release
1994
1995
1996
1997
1998
1999
2000
2001
2002
Revised Distress Identification Manual released April 2002
2003
Revised Distress Identification Manual released October 2003
2004
2005
2006
2007

6.4.2 References Used in Profile Measurement

Field Manuals Used in Profile Measurement

Collection of longitudinal profile data with the 690DNC model KJ Law profilers was governed by the following three versions of the guidelines.

The four T6600-model KJ Law profilers were implemented officially by directive on October 14, 1996. The following manuals provide the guidelines used in collecting longitudinal profile data with the T6600s.

Collection of longitudinal profile data with the International Cybernetics Corporation (ICC) MDR4086L3 inertial profilers began on October 9, 2002, by directive. The following manuals provide the guidelines used in collecting data with these units.

Software Manuals Used in Profile Measurement

Each of the following manuals is provided for use with the software used to review and prepare the longitudinal profile data for entry into the database.

In 2005, software was provided to the regions to facilitate additional review of the profile as required. This software exports the data into a format commonly used by several other different pieces of software for manipulation and evaluation of longitudinal profile data.

6.5 Surface friction Measurements

Friction measurements on LTPP test sections were originally required. Data were to be collected with a locked wheel skid tester. Collecting these data as part of the LTPP program is now optional. Collection of surface friction data is governed by section 3.2 of the DCG as referenced at the beginning of this chapter.


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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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