Inertial Profiler Certification for Evaluation of International Roughness Index (2018)

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86 Many state DOTs use IRI as the smoothness index for construction acceptance. The state DOTs also use IRI to keep track of the roughness of the state pavement network and for HPMS submittal. As part of the MAP-21 Act and FAST Act requirements, state DOTs are also required to use the IRI as a performance measure for ride quality. Data collected by an inertial profiler are used to compute the IRI for these purposes. An inertial profiler is considered to be certified when it has demonstrated that it is capable of collecting profile data from which repeatable and accurate IRI values can be obtained, based on a specified set of criteria. The accuracy of the profiler is evaluated by comparing the data collected by the profiler with data collected by a reference device. The inertial profiler operator must be knowledgeable in the operation of the equipment to collect error-free data. Agencies certify profiler operators who have demonstrated that they are competent to operate a profiler and analyze the collected data, based on a specified set of criteria. The primary objective of this study was to document the state of practice followed by state DOTs in the U.S. for certification of inertial profilers that are used to collect profile data for computation of IRI for construction acceptance and network-level data collection, as well as the certification procedures for inertial profiler operators. A survey of state DOTs was performed to gather information related to certification of equipment that is used to collect network-level profile data and to collect profile data for computation of IRI for construction acceptance. The survey also gathered information on cer- tification of profiler operators and procedures for QC of the collected data. Responses were received from 44 state DOTs, which is a response rate of 88%. A survey was also sent to three vendors who perform a majority of the network data collection in the U.S. under contract to state DOTs. Responses were received from two vendors. Summary of Findings: IRI for Construction Acceptance Thirty-eight of the state DOTs that responded to the survey (86% of the responding state DOTs) indicated that they use an IRI-based smoothness specification for construction acceptance. (Two state DOTs indicated that they use an HRI-based smoothness specification. As HRI is highly correlated to IRI, for the purpose of this synthesis the HRI was considered to be equivalent to IRI). All of the 38 state DOTs use an IRI-based smoothness specification on asphalt-surfaced roadways. Twenty-six of the responding state DOTs (59% of the responding state DOTs) use an IRI-based smoothness specification on PCC-surfaced roads, with nine of the responding state DOTs (20% of responding state DOTs) using such a specification on bridge decks. Of the 38 state DOTs that responded and are using an IRI-based smoothness specification, the collection of smoothness data on the final paved surface for construction acceptance is C H A P T E R 7 Conclusions and Further Research

Conclusions and Further Research 87 performed by the state DOT in 16 states, by the contractor in 18 states, and by the state DOT as well as the contractor in two states. In the states that allow contractors to collect smoothness data for construction acceptance, the state DOT performs QA testing on the data collected by the contractor. For QA testing, the state DOT 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. Of the 38 state DOTs that responded to the survey indicating that they use an IRI-based smoothness specification, 27 state DOTs indicated that a certified profiler must be used to collect data on the final paved surface for construction acceptance. In-state profiler certification programs are in place in 25 states. Two of the state DOTs that do not have an in-state profiler certification program take their profiler to a certification facility in another state for certification. The test section(s) for certifying profilers is located on in-service roads in the majority of the states, while they are located in a facility that is not subjected to public traffic in others. In the majority of the states, the profiler certification program is administered by the state DOT, while in a few states, the program is administered by a university-affiliated institution. All states that have an in-state profiler certification program in place indicated that the certification is valid for 1 year. The number of test sections that are used to certify a profiler varies from state to state, with 11 states using one test section, seven states using two test sections, and seven states using more than two test sections. Of the 25 states that have in-state certification programs, six states do not have a smoothness specification for PCC pavements. Of the 19 states that do have a smoothness specification for PCC, 12 states do not use a PCC section for certification and certify the profiler only on AC-surfaced test section(s). The procedures used to certify the profiler in the decreasing order of use are an agency-developed procedure that includes the cross-correlation method speci- fied in AASHTO Standard R 56-14 to analyze the data, procedures described in AASHTO Stan- dard R 56-14, and an agency-developed procedure that does not use the cross-correlation method to analyze the data. Overall, 18 of the 25 state DOTs that have an in-state certification program use a certification procedure that includes the cross-correlation method specified in AASHTO Standard R 56-14. The majority of the states use 0.1-mi-long test sections to certify the profiler with the SurPRO—a rolling device—being used to collect the reference data in all but two cases. Two state DOTs have a program for approving profilers, where the IRI from the state DOT– owned profiler(s) is considered to be the reference IRI. As a reference device is not used in this procedure to obtain the reference IRI, the procedure is referred to as approving profilers rather than certifying profilers. Several state DOTs that currently do not certify profilers indicated that their agencies do not require a profiler that collects smoothness data for construction acceptance to be certified. Several state DOTs that do not certify their profilers indicated that they verify the consistency of the equipment by collecting data at regular intervals on an established verification section and comparing the current data with previously collected data. Twenty-two of the 38 state DOTs that responded to the survey indicating that they use an IRI- based smoothness specification allow contractors to collect smoothness data on the final paved surface for construction acceptance. Out of these 22 state DOTs, 18 certify contractor-owned pro- filers, with two approving profilers. A fee is levied for certifying contractor-owned profilers in six states. Most of these state DOTs do not specify the height-sensor type in the profiler that is used to collect the smoothness data for construction acceptance. A few state DOTs require data collection on PCC pavements to be performed with profilers equipped with LLs. It is well known that profilers with SS lasers do not collect accurate data on longitudinally textured surfaces—such as longi- tudinal tining or diamond grinding—and the IRI computed from such data will have an upward bias. Therefore, it is expected that contractors will use an LL to collect data on such surfaces. Sixteen state DOTs that do not allow contractors to collect data for smoothness acceptance collect this data using state DOT–owned equipment, but only four of these state DOTs require

88 Inertial Profiler Certification for Evaluation of International Roughness Index the state DOT profiler operator to be certified. The operator certification procedures in each state require the operator to perform a combination of the following items to be certified: pass a practical exam, pass a written exam administered in the classroom, attend a class describing profiler operations, take an online class, and pass an online exam. The procedures that are used by the states in decreasing order of use are: pass a practical exam, pass a written exam administered in the classroom, attend a class describing profiler operations, take an online class, and pass an online exam. The most common duration for the validity of operator certification is 3 years. However, the duration is 1 year in some states and 5 years in others. In most states the profiler operator certification program is administered by the state DOT, but in a few states this program is administered by a university or a technical college that also provides certification in various other technical fields in the construction area (e.g., asphalt density testing). Most state DOTs indicated that the block check, bounce test, and the verification of the DMI is performed on the state DOT–owned profilers before collecting data. Eleven of the 22 state DOTs that allow contractors to collect data do not require the state DOT representative to observe the contractor operator performing any of these tests before collecting data. The QA procedures followed by the state DOTs to verify the contractor-collected data vary from state to state. In a few states, the DOT collects data on the entire project for all projects, while in others a specific percentage of projects are verified. Typically, the state DOT will collect data on a project if an issue is flagged. The procedure for handling disputes with a contractor regarding issues with the data collected by the state DOT typically involves performing an investigation on the collected data to verify the accuracy of the data. In the states that do not accept data collected by the contractor for smooth- ness acceptance, the contractor is free to collect their own data for QC purposes. Therefore, these contractors could also challenge the data collected by the state DOT if the DOT-collected data results in higher IRI values. If a state DOT does not have a profiler certification program in place, the state DOT may have difficulties in proving the accuracy of the data collected by state DOT–owned profilers if a contractor challenges the validity of the data collected by them. Summary of Findings: Network-Level IRI The profile data for computation of IRI at network level is collected either by the state DOT, a vendor under contract to the state DOT, or both. Of the 44 state DOTs that responded to the survey, 18 (41% of responding DOTs) indicated that the state DOT exclusively collects all of the network- level data, while 17 (39% of the responding DOTs) indicated that a vendor exclusively collects the data. The other nine state DOTs indicated that both the state DOT and the vendor collect the data. The survey indicated that in 27 states (61% of responding states) the state DOT collects all or some of the network-level data, and in 25 states (57% of the responding states) the vendor collects all or some of the data. In the 27 states where the state DOT collects all or some of the data, the state DOT–owned profiler(s) that collect the data are certified in only 12 states. In the 25 states where the vendor collects all or some of the data, the vendor-owned profiler(s) is certified in-state by the state DOT before data collection in seven states. Three states indicated that the vendor provides documen- tation to indicate that the profiler has been certified at an out-of-state location. In the states where the profilers that collect network-level data are certified, the certifica- tion is performed using the same sections and methods that are used in these states to certify profilers that collect data for construction acceptance. In several states where the state DOT does not certify the state DOT–owned equipment, the state DOT collects data with the profiler at established verification sections to verify that the data collected by the profiler are consistent

Conclusions and Further Research 89 by comparing the collected data with previously collected data. In some states where vendors’ equipment is not certified, the state DOT has established verification sections where the data collected by the vendors’ equipment are compared with data collected by the state DOT–owned equipment to determine whether the data compare within a specified threshold before the vendor is allowed to collect data. The majority of the state DOTs also require the vendor to collect data at verification sections established throughout the states during data collection as a QC measure on the vendor-collected data. The data collected by the vendor at these verification sites are compared to data collected by the state DOT–owned profiler at these sites or with historical data at the sites. Several state DOTs that use their own equipment to collect data also use verification sections established throughout the state or a verification section that is located close to the office as a QC measure to compare current data with previously collected data. Of the 27 state DOTs out of 44 that responded to the survey indicating that they use state DOT–owned equipment to collect network-level data, only three indicated that profiler opera- tors require certification. Of the 25 states that allow vendors to collect data, only two states require operators to be certified in-state. A fee is levied in one state for certifying operators, while in the other state the fee for operator certification is included in the fee charged for certifying the profiler. Several states indicated that vendors are responsible for certifying their operators. Twelve of the 44 state DOTs that responded to the survey indicated that they have a written data quality management plan, while six state DOTs indicated that they are currently developing a plan. The items addressed in the data quality management plan regarding profile data collection includes equipment calibration, operational checks on the equipment, testing at verification sites, routines for checking whether the data are within acceptable levels, and routines for checking data with previously collected data. Some state DOTs indicated that although they do not have a written data quality plan, they do have procedures in place for addressing the previous items. Responses received from the vendors provided the following procedures that they use to perform QC on the collected data: • Perform in-house testing to ensure proper calibration of the equipment. • Perform block check and bounce test daily. • Monitor the height-sensor data, accelerometer data, and profile data for each wheelpath in real time. These data are displayed graphically in real time, and all data are monitored automatically during collection. • Process the collected data each day, and flag sections that have abnormal values so that they can be inspected further. The report that is generated is sent to the central office each night. • Collect data weekly at verification sites. These sites are either established by the state, or the vendor establishes verification sites as part of the data-collection contract. • Select random locations, and request that the field crew re-collect data on routes where data were collected previously to verify the IRI values. • Plot current data with historical data to verify IRI values, and verify any discrepancies to determine whether an overlay or maintenance project is the reason for the discrepancy. • Use images from the imaging system of the vehicle to evaluate any issues noted on the data. Summary of Overall Findings Twenty-seven of the 44 state DOTs that responded to the survey require a certified profiler to be used to collect smoothness data on the final paved surface for construction acceptance. The survey indicated that state DOTs collect all or some of the network-level data in 27 of the

90 Inertial Profiler Certification for Evaluation of International Roughness Index 44 states that responded to the survey, but the state DOT–owned equipment is certified in only 12 states. The survey also indicated that a vendor collects network-level data in 25 of the 44 states that responded to the survey, but the vendor-owned equipment is certified in-state only in seven states, with three states responding that the vendor provides documentation that the profiler has been certified at an out-of-state location. Of the 25 states that have an in-state certification pro- gram to certify profilers that collect smoothness data for construction acceptance, only 12 states require profilers that collect network-level data to be certified. These results show certification of profilers that collect data for construction acceptance is more common than certifying profilers that collect network-level data. The IRI computed from the data collected for construction acceptance is used as the basis of pay adjustments, based on the smoothness specification in a state. Therefore, the states appear to be putting more emphasis on certifying profilers that collect smoothness data for construction acceptance to ensure that accurate data are being collected. Most states that are using a vendor to collect network data are assuming that the vendor will use properly calibrated equipment to collect the data and use data collected at verification sections by the contractor-owned equipment for QA. Several state DOTs indicated that their agency does not require profilers that collect smooth- ness data for construction acceptance or network-level data collection to be certified. Therefore, in these states, the impetus for establishing such a program will require the state DOTs to have a policy to certify profilers that collect these data. At present, profiler certification programs are either administered by a state DOT or a university-affiliated institution, while profiler operator certification programs are administered by a state DOT, a university-affiliated institution, or a technical college. Currently, there is no national certification agency that is involved in profiler certification or profiler operator certification. The recently enacted rules in National Performance Management Measures (23 CFR Part 490) indicate that each state DOT is required to develop and use a data quality management program approved by the FHWA that addresses the quality of all collected data, regardless of the acquisi- tion method. The rule indicates that the program shall include methods and processes for data collection equipment and certification and mentions that it is expected that state DOTs would specify AASHTO R 56-14 or an equivalent method for certification of equipment. Because of this requirement, it is expected that there would be more emphasis being placed on developing certification programs for profilers that collect network-level data. Barriers to Implementing a Profiler Certification Program Some of the obstacles faced by state DOTs in setting up a profiler certification program to certify equipment could include • Finding a suitable facility that is closed to public traffic or finding suitable locations on in-service roads for setting up test sections needed for a certification program, • Finding all of the surface types that are needed for profiler certification at a suitable facility or locating these sections close to each other for test sections that are established on in-service roads, • Lack of a suitable reference device to perform reference profile measurements on desired surfaces and/or funding issues in procuring such equipment, • Lack of personnel to administer a profiler certification program, and • Knowledge of persons within the state DOT to set up and administer a profiler certification program.

Conclusions and Further Research 91 The availability of personnel and cost will impact the type of certification program that a state can set up. For example, limitation on personnel and budget may only allow a state DOT to set up a single site for certifying profilers. Gaps in Knowledge and Suggestions for Future Research The following are the gaps in knowledge and suggestions for future research or action: 1. Data collection with inertial profilers is a complicated subject. There is a learning curve one must go through to understand how profilers operate, what procedures to follow for collecting accurate data, and how to analyze the collected data. Development of a document that addresses all aspects of inertial profiler data collection and analysis is needed, which will be valuable for a person who is new to this field. The Little Book of Profiling (Sayers and Karamihas 1998) is an excellent document that condenses information related to profiling. However, this document was published in 1998, and many changes have taken place in the profiling arena over the last 2 decades. 2. Developing a document on how to set up a profiler certification program will be useful for state DOTs that are planning to set up a profiler certification program. Although AASHTO Standard R 56-14 does address profiler certification, such a document can provide more comprehensive information and include information about profiler certification programs that have been successfully administered by state DOTs over the past years. 3. Several state DOTs have constructed test tracks specifically for certifying profilers. In these test tracks, pavement sections are constructed such that they meet specific IRI levels. Usually, constructing a smooth test section does not present an issue, but constructing a test section that is not smooth and has a specific IRI target level could be difficult. A guidance document on constructing a test track for profiler certification that summarizes the knowledge from state DOTs that have constructed such test tracks will be useful for an agency that is considering building such a test track. 4. Developing a template that can be used in a contract by a state DOT or any other highway agency when procuring the services of a vendor to collect network-level IRI data will be useful for state DOTs. This template can address issues such as requirements of the profiler (e.g., height-sensor type, sensor spacing, and data-recording interval), profiler certification/ verification procedures, QC procedures during data collection, and so on. Existing contracts used by the state DOTs can be reviewed to develop this template. 5. A mechanism to provide technical assistance to state DOTs that are developing a profiler certification program is needed. 6. Establishment of regional certification sites will be helpful for state DOTs that do not have a certification program for their equipment. Such sites will also provide a venue for contractors and vendors to certify their equipment. Perera (2014) performed a study on establishing regional certification centers for inertial profilers. Information in this report will be useful for any organization that is investigating how to set up a regional certification center.