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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
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Page 6
Page 7
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
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Page 7
Page 8
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 8
Page 9
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 9
Page 10
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 10
Page 11
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 11

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6 This chapter describes the background information related to this study, the scope of the study, the study approach, the terminology used in the synthesis, and the organization of the synthesis. Background The traveling public judge the condition of a road by its ride quality. Recognizing that ride quality of roads is important to the traveling public, state departments of transportations (DOTs) have been using smoothness specifications to ensure that smooth pavements are constructed. A smoothness specification indicates the level of roughness that may be present on the final paved surface of a pavement to justify full payment to the contractor. Studies have shown that pavements that are built smoother stay smooth longer and provide a longer service life (Smith et al. 1997; Perera and Kohn 2001), which is another incentive for state DOTs to ensure that pavements are constructed to a high smoothness level. Today, many state DOTs use the international roughness index (IRI), which is a parameter that is commonly used to judge the ride quality of roads and the smoothness of the final paved surface of a roadway. The profile data of the pavement collected with an inertial profiler is used to compute the IRI of the road. Many state DOTs apply a negative pay adjustment when the final surface is rougher than the specified IRI threshold and a positive pay adjustment when it is smoother than the specified level. State DOTs also require the contractor to correct the pave- ment surface to address areas of localized roughness on the final paved surface of a roadway that is identified based on the procedures described in the smoothness specification. Some state DOTs use their own equipment to collect profile data on the final paved surface of a roadway to assess the roughness level, while others allow the contractor or a testing company hired by the contractor to collect the data. The state DOTs that allow contractors to collect data may collect data on the entire project, a part of the project, or on a sample of projects to verify the data collected by the contractor. State DOTs collect profile data on their highway network and compute a roughness index from this data to assess the roughness level of the highway network. The IRI is commonly used as this roughness index. Some state DOTs collect network-level profile data using their own equipment, while others contract this service to a vendor. The IRI values are stored in the state’s pavement management system, typically at 0.1-mi intervals. These IRI data are used to evaluate the functional status of the pavement network, identify projects for rehabilitation, and determine budget. The Federal Highway Administration (FHWA) requires state DOTs to annually submit to the Highway Performance Monitoring System (HPMS) roughness data for the following roadways in their state: National Highway System (NHS) roads; non-NHS freeways, expressways, and C H A P T E R 1 Introduction

Introduction 7 principal arterials; and HPMS sections that are located on rural minor arterials (FHWA 2016). The roughness data must be submitted with regard to the IRI. Some of the roadways whose IRI data must be submitted to the HPMS may not be under the jurisdiction of the state DOTs. Therefore, the state DOTs need to collect profile data on these roadways to compute IRI to be submitted to the HPMS, in addition to collecting data on the state highway network. The FHWA uses the IRI data submitted to the HPMS to assess the condition of the nation’s highways. The IRI data submitted to the HPMS by each state annually is summarized in a document called Highway Statistics (FHWA 2015A). The summarized IRI data are also included in the document Status of Nation’s Highways, Bridges, and Transit: Conditions and Performance (FHWA 2015B), which is submitted to Congress by the U.S. Department of Transportation biennially. As IRI data submitted by individual states to the HPMS are used to generate these reports, it is important that all profilers that collect such data be capable of collecting repeatable and accurate data. The Moving Ahead for Progress in the 21st Century (MAP-21) Act and Fixing America’s Surface Transportation (FAST) Act require state DOTs to establish performance measures for pavement and bridge condition. Based on these acts, the FHWA released the final rule for state DOTs to use to carry out the National Highway Performance Program in January 2017 (Federal Register 2017). This rule was published as 23 CFR Part 490 and is titled National Performance Management Measures: Assessing Pavement Condition for the National Highway Performance Program and Bridge Condition for the National Highway Performance Program. Under this rule—for pavements—state DOTs are required to establish separate performance targets for the interstate system and the non-interstate NHS roads within their state. The performance targets for pavements are to be established with regard to roughness, cracking, rutting, and fault- ing. The IRI is the metric to be used to assess roughness. To have uniformity among the states with respect to the performance target for IRI, all profilers that are used to collect profile data for computation of IRI must be capable of collecting repeatable and accurate profile data. An inertial profiler that is used to collect profile data for computing IRI—whether it be for accepting construction, collecting data on the state’s pavement network, or gathering data on HPMS sections located on the off-state system—must be capable of collecting repeatable and accurate profile data for computation of IRI. An inertial profiler that has demonstrated it is capable of collecting profile data from which repeatable and accurate IRI values can be obtained based on a specified set of criteria is considered to be certified. The repeatability of a profiler is judged by performing multiple passes of the equipment over the same test section and deter- mining if the IRI values obtained for the repeated runs meet a specified criteria. The accuracy of a profiler is evaluated by comparing the IRI obtained from the profiler data to IRI computed from data collected by a reference device on the same section. If the IRI for the profiler and the reference device agree with each other within a specified tolerance, the profiler is considered to be collecting accurate data. A profiler is typically certified at the beginning of the year before it starts collecting data either for network-level data collection or on construction projects for smoothness acceptance. The inertial profiler operator must be knowledgeable of equipment operation to collect error-free data. The operator must be able to calibrate the various profiler components, perform pre-operational equipment checks prior to data collection to ensure all profiler components are functioning properly, follow correct operational procedures when collecting data, evaluate the data that are being collected to ensure the data are error free, and compute roughness indices such as IRI from the collected data. Several state DOTs have certification programs to certify profiler operators who have demonstrated the ability to satisfy these criteria. A certified profiler operated by a certified operator is expected to collect profile data that will result in repeatable and accurate IRI data.

8 Inertial Profiler Certification for Evaluation of International Roughness Index Scope of the Study The primary objective of this study was to document the state of practice followed by state DOTs in the U.S. for 1. Certification of inertial profilers that are used to collect profile data for computation of IRI for construction acceptance and network-level data collection. 2. Certification procedures for inertial profiler operators. A survey of state DOTs in the U.S. was performed to gather information on the following topics related to certification of equipment that is used to collect profile data for computation of IRI for construction acceptance and network-level data collection, certification of profiler operators, and procedures for quality control (QC) of the collected data: • Reference device used to collect reference data for the certification of the profiler; • Surface material types, ranges of roughness, and pavement surface textures used for certification; • Test procedure used for certification of equipment; • Criteria used for certification of operators; • Certification reciprocity among states for equipment and operators; • Cost of certification for equipment and operators; • Documents provided after certification for equipment and operators; • Management of the certification facility; • Duration of validity of the certification for equipment and operators; and • Procedures/processes used to monitor the inertial profiler operation and to ensure quality of the collected data subsequent to certification. The study also included performing a literature review to gather background information related to profile data collection and profiler certification. Study Approach A literature review was performed to gather background information on profile data collection, including the types of inertial profilers; height-sensor types used in inertial profilers; the effect of texture on data collected by various height-sensor types; types of reference profilers; procedures for certification of inertial profilers, including procedures used in other countries; procedures to be followed for operation of inertial profilers; and resources that are available for pavement smoothness information and software for data analysis. A survey of state DOTs was performed to gather information about the following topics: • Number of inertial profilers owned by the state DOTs; • Type of reference device owned by the state DOTs; • Whether the state DOTs use IRI for construction acceptance, and if so, whether it is used for AC pavements, PCC pavements, and bridge decks; • Approximate percentage of the state’s highway system that is surfaced with AC and PCC; • Whether the state DOTs have a policy regarding roadways on which the states’ smoothness specification is used; • Whether the state DOTs allow contractors to collect profile data for construction acceptance; • Whether the state DOTs or a vendor collects network-level data on the state highway system and at HPMS sections that are located on the off-state system; • Certification procedures for inertial profilers that are used to collect data for computation of IRI for construction acceptance and network level data collection; • Certification procedures for inertial profiler operators that are used to collect data for com- putation of IRI for construction acceptance and network-level data collection;

Introduction 9 • Surface material types, ranges of roughness, and surface textures of test sections used for certification; • Procedure used for certification of equipment; • Procedure used for certification of operators; • Documents provided after certification of equipment and operators; • Certification reciprocity among states for equipment and operators; • Cost of certification for equipment and operators; • Agency managing the certification facility for profiler certification; • Duration of validity of the certification for both equipment and operators; • Pre-operational checks performed on the profiler before collecting data for construction acceptance; • Quality assurance (QA) procedures used on contractor-collected data for construction accep- tance and procedures for handling disputes with contractors; • Operation procedures during network-level data collection; • Processes used to monitor the data collected by inertial profilers at network-level subsequent to certification; and • Whether the state has a data quality management plan, and—if a plan is available—the items that are covered in the plan. Appendix A includes the survey that was developed for this project and sent to all 50 state DOTs. Twenty-two states participated in the pooled fund TPF 5(063), Improving the Quality of Highway Profile Measurements. The survey was sent to the state pooled fund representative in these 22 states. For the other 28 states, the survey was sent to the person identified within the state DOTs as handling profiler certifications; or if such a person could not be identified, to the pavement management engineer of the state. The survey was conducted through a web-based program. Forty-four state DOTs responded to the survey, which represents a response rate of 88%. The state DOTs in Hawaii, Idaho, Indiana, Nebraska, South Carolina, and Wyoming did not respond to the survey. In the survey, participants were asked whether they wanted anonymity with respect to the provided answers, and 15 respondents requested anonymity. The responses provided by the state DOTs to the survey are included in Appendix B. Appendix C includes the survey that was sent to three vendors who perform most network- level surveys under contract to state DOTs. Responses were received from two vendors, and the provided responses are summarized in Appendix D. In addition, interviews were conducted with personnel involved in profiler certification in several states to gather detailed information on the certification procedures used in their states. Input was also sought from select states on challenges encountered during profiler certification and the important items to consider when setting up a profiler certification program. Terminology The definition of some of the key terms used in this synthesis are provided in this section. The definition of these terms are specific to the context of this synthesis. • Accuracy: The degree to which the result of a calculation conforms to a reference standard. • Certified Operator: An operator who has been certified by some agency as proficient in performing calibration of components in the profiler requiring calibration, performing calibration checks on the profiler, operating the profiler to collect data, and analyzing the data collected by the profiler. The operator may also be required to be knowledgeable about data collection procedures, data analysis procedures, and data submittal procedures of a specific state DOT.

10 Inertial Profiler Certification for Evaluation of International Roughness Index • Certified Profiler: A profiler that has demonstrated that it can meet a repeatability and an accuracy criterion based on the IRI within a specified threshold. The accuracy criterion is based on agreement with data collected by a reference device. • Contractor: The company that has been awarded a roadway construction project and is responsible for collecting profile data on the final paved surface of the pavement to deter- mine the IRI for construction acceptance if the state DOT requires the contractor to collect the data. • Department of Transportation: The agency that is responsible for the state-maintained highway system in the state. • Inertial Profiler: A vehicle that is equipped with an inertial profiling system that comprises height sensors, accelerometers, a distance measuring system, and a computer and is capable of producing the longitudinal profile of a road. • International Roughness Index: A statistic used to determine the amount of roughness in a measured longitudinal profile. The IRI is computed from a single longitudinal profile using a quarter-car simulation at 50 mph (Sayers 1995). The source code for calculating the IRI from a longitudinal profile is included in ASTM 1926 (ASTM 2017A). • Longitudinal Profile: A two-dimensional slice of the roadway surface taken along the travel direction, such as along the wheelpath. It represents the perpendicular deviations of the pave- ment surface from an established reference plane parallel to the horizontal (AASHTO 2017A). • Mean IRI: The MIRI or the average of the IRI values that are obtained for the left and the right wheelpaths. • Repeatability: Consistency in successive measurements of the same quantity. It is a quantifier of the variability in measurement using the same equipment and operator. • Roughness: The deviation of a surface from a true planar surface with characteristic dimensions that affect vehicle dynamics, ride quality, dynamic loads, and drainage (ASTM 2017B). • Vendor: A company that is contracted by a state DOT to collect network-level profile data for IRI computation. • Verification: Comparing the data collected by a profiler at a test section with the data collected previously by the profiler at the same section; or comparing the data collected by a profiler at a test section with data collected by another profiler at the same test section. Organization of the Synthesis Chapter 2 of this report presents background information about inertial profilers and pro- file data collection. The following topics are addressed in this chapter: description of the types of inertial profilers; height-sensor types used in inertial profilers; effect of texture on the data collected by different types of height sensors; types of reference profilers; procedures used for certification of inertial profilers; network-level data collection; operational procedures for collecting profile data; and resources for information related to pavement smoothness, includ- ing software for analyzing profile data. Chapter 3 presents the information obtained from the survey regarding inertial profilers and reference profilers owned by the state DOTs. Chapter 4 presents the information obtained from the survey regarding whether the state uses IRI as the smoothness index for construction acceptance, and if so, whether it is used for AC pavements, PCC pavements and bridge decks; and the state DOTs’ policy regarding the use of a smoothness specification for the final paved surface of a roadway. Chapter 5 presents information obtained from the survey related to profile data collection for construction acceptance for computing IRI, including the procedures used for certification of equipment and operators and the procedures used to ensure the quality of the collected data. Chapter 6 presents information obtained from the survey related to network-level data collection, including the procedures used for certifica- tion of equipment and operators and the procedures used to ensure the quality of the collected

Introduction 11 data. Chapter 7 presents the conclusions from the study, gaps in knowledge, and suggestions for future research. Appendices A and C, respectively, include the survey that was sent to the state DOTs and the vendors. Appendices B and D, respectively, include the response to the survey received from state DOTs and the vendors. As described previously, the survey asked participants whether they wanted anonymity with respect to the provided answers. Any state DOTs’ names mentioned in this synthesis are of states that did not request anonymity.

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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 526: Inertial Profiler Certification for Evaluation of International Roughness Index determines the state of practice of certification of inertial profilers at the national and international levels. Inertial profilers are used to collect the repeatable and reproducible road profiles analyzed to calculate a smoothness or ride quality index, the most common of which—the International Roughness Index (IRI)—is a performance measure that state departments of transportation (DOTs) must report to the Federal Highway Administration (FHWA) as part of Highway Performance Monitoring System/Moving Ahead for Progress in the 21st Century (HPMS/MAP-21) Act and Fixing America’s Surface Transportation (FAST) Act requirements. The information in this report can help ensure that accurate data are collected both for smoothness specifications at the project level and for MAP-21 Act and FAST Act requirements that the states provide accurate and consistent IRI data.

The report is accompanied by the following appendices:

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