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

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1 Road users judge the condition of a road by its ride quality. Recognizing the importance paid by road users to smooth pavements, state departments of transportations (DOTs) have implemented smoothness specifications for new pavements, as well as for rehabilitated pavements, to ensure the final paved surface of the roadway will have high smoothness. The smoothness specification indicates the level of smoothness that has to be achieved for the roadway to allow the paving contractor to obtain full payment. Studies have shown that pavements that are built smoother stay smooth longer and provide a longer service life, which is another incentive for state DOTs to ensure that pavements are constructed to a high smoothness level. As an incentive for contractors to construct smooth pavements, many state DOTs specify a positive pay adjustment when the constructed pavement is smoother than the specified level. State DOTs usually apply a negative pay adjustment when the final surface is rougher than the specified smoothness threshold. Today, the majority of 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 are used to compute the IRI of the road. The state DOT or a vendor contracted by the DOT collects profile data on the state high- way network—and computes a roughness index from these data—to assess the roughness level of the highway network. The IRI is commonly used as this roughness index. 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 principal arterials; and HPMS sections that are located on rural minor arterials. 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 DOT. Therefore, the state DOT needs to perform roughness data collection on these roadways to be submitted to the HPMS, in addition to collecting data on the state highway network for their own use. The IRI data submitted to the HPMS by each state annually is summarized in a document called Highway Statistics and used by federal agencies to assess the condition of the nation’s pavements. The summarized IRI data are also included in the document called Status of Nation’s Highways, Bridges, and Transit: Conditions and Performance, which is submitted to Congress by the U.S. Department of Transportation biennially. 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 S U M M A R Y Inertial Profiler Certification for Evaluation of International Roughness Index

2 Inertial Profiler Certification for Evaluation of International Roughness Index 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. 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. For pavements, under this rule state DOTs are required to establish 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 faulting. The IRI is the metric to be used to assess roughness. 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 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 repeatability of a profiler is judged by performing multiple passes of the equipment over the same test section and determining 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. State DOTs that certify profilers have procedures on the number of test sections to be used for certification, rough- ness levels of the test sections, and the criteria that the profiler must pass to be certified. 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 in the operation of the equipment 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 collect- ing 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. An operator can be certified by passing a program set up by an agency that will evaluate the operator’s competency to satisfactorily perform the above tasks. A certified profiler operated by a certified operator is expected to collect profile data that will result in repeatable and accurate IRI data. 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 computing IRI for construction acceptance and at the network level, as well as the certifica- tion procedures for inertial profiler operators. A literature review was initially performed to gather background information related to profile data collection and certification. The literature review gathered information on the types of inertial profilers used for data collection, height-sensor types used in inertial profilers, the effect of texture on data collected by various height-sensor types, types of refer- ence profilers, procedures for certification of inertial profilers, operational procedures for collecting data, and resources that are available for pavement smoothness information and software for data analysis. A survey of state DOTs in the U.S. was performed to gather information related to certifi- cation of equipment that is used to collect profile data for computation of IRI for construc-

Summary 3 tion acceptance and at network level, certification of profiler operators, and procedures for quality control (QC) of the collected data. Responses were received from 44 state DOTs, which is a response rate of 88%. Thirty-eight of the state DOTs that responded to the survey (86% of responding state DOTs) indicated that they use IRI-based smoothness specifications. (Two state DOTs indicated that they use half-car roughness index [HRI] as the smoothness index for construction acceptance. But as HRI is highly correlated to IRI, for the purpose of this synthesis the HRI was considered to be equivalent to IRI). All of these 38 state DOTs use the IRI-based smoothness specifi- cation on asphalt-surfaced roadways, with 25 state DOTs also using such a specification on portland cement concrete (PCC) surfaced roads. Of the states using an IRI-based smooth- ness specification, the collection of smoothness data on the final paved surface for construc- tion acceptance is performed by the DOTs in 16 states, the contractor in 18 states, and the DOTs as well as the contractor in two states. In the states that allow contractors to collect data, the DOTs may collect data on the entire project, on 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 use IRI-based smoothness specifications, 27 indicated that a certified profiler must be used to collect the smoothness data on the final paved surface for construction acceptance. In-state profiler certification programs are in place in 25 states. Two of the DOTs that do not have an in-state profiler certification program take their profilers to a certification facility in another state for certification. The test section(s) for certifying profilers are 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 DOTs, while in a few states the program is administered by a university-affiliated institution in the state. 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 profilers that collect profile data for construction acceptance to be certified, with these agencies also indicating that they do not own a reference data collection device. Several state DOTs that do not certify their profilers indicated that they verify the consis- tency of the equipment by collecting data on an established verification section at regular intervals and compare the collected data with data collected previously by the profiler at this section. Twenty-two state DOTs allow contractors to collect profile data on the final paved surface for construction acceptance. Out of these 22 state DOTs, 18 certify contractor-owned profilers, with two state DOTs approving profilers. A fee is levied for certifying contractor- owned profilers in six states. The number of test sections 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 smooth- ness specification for PCC, 12 states do not use a PCC section for certification and certify the profiler only on an asphalt concrete (AC)-surfaced test section or sections. The procedures used to certify the profiler in the decreasing order of use are an agency-developed procedure that includes the cross-correlation method specified in AASHTO Standard R 56-14 to ana- lyze the data, procedures described in AASHTO Standard R 56-14, and an agency-developed

4 Inertial Profiler Certification for Evaluation of International Roughness Index 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 rolling device being used to collect the reference data in all cases except for two. Sixteen state DOTs that do not allow contractors to collect data for smoothness accep- tance collect this data using state DOT–owned equipment, but only four of these state DOTs require the DOTs’ 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 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 DOTs, 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). Network-level IRI data collection includes collecting data on the state pavement net- work and at locations that are on the off-state system and are required for submittal to the HPMS. Of the 44 state DOTs that responded to the survey, 18 indicated that the DOTs exclusively collect all of the network-level data, while 17 state DOTs indicated that a vendor exclusively collects the data. The other nine state DOTs indicated that both the DOTs and the vendor collect the data. The survey indicated that in 27 of the states that responded to the survey, the DOTs collect all or some of the network-level data, and in 25 states the vendor collects all or some of the data. In the 27 states where the DOTs collect all or some of the network data, the 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 network data, the vendor-owned profiler(s) are certified in state before data collection in seven states. Three states indicated that the vendor provides documentation to confirm 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 certification 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 DOTs do not certify the DOT-owned equipment that collects network-level data, the DOTs collect data with the profiler at established verification sections. This verifies that the data collected by the profiler is consistent by comparing the collected data with previously collected data. In some states where the vendor’s equipment is not certified, the DOTs have established verification sections where the data collected by the vendor’s equipment are compared with data collected by the DOT-owned equipment to see if 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 network-level 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 DOT-owned profiler at these sites or with histori- cal 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 DOTs indicated that

Summary 5 profiler operators require certification. Of the 25 states that allow vendors to collect data, only two states require the vendor’s 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 the vendors are responsible for certifying their operators. Of the 25 states that have an in-state certification program to certify profilers that collect smoothness data for construction acceptance, only 12 states require the profilers that collect network-level data to be certified. These results show that certification of profilers that collect data for construction acceptance is more common that certifying the profilers that collect network-level data. The IRI computed from the data collected for construction acceptance is used as the basis of payment and 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. 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 develop- ing a plan. The items addressed in the data quality management plan regarding profile data collection include equipment calibration, operational checks on the equipment, testing at verification sites, routines for checking if 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 management plan, they do have procedures in place for addressing the above items. 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 method of acquisition. The rules indicate that the program shall include methods and processes for data collection equipment and certification and mention that state DOTs are expected to specify AASHTO R 56 or an equivalent method for certification of equipment. Because of this requirement, it is expected that there will be more emphasis placed on developing certification programs for profilers that collect network-level data.