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93 acceptance: A process (i.e., sampling, testing, and inspection) used by the agency to determine the degree of compliance with contract requirements and to determine the corresponding value for a given product (AASHTO 2006). acceptance sampling and testing: Sampling and testing performed by the agency or designated agent to evaluate acceptability of the final product. Also referred to as verification sampling and testing when used to validate the contractorâs data (AASHTO 2006). accuracy: The degree to which a measurement, or the mean of a distribution of measurements, tends to coincide with the true population mean (AASHTO 2006). assurance: Reporting, training, and process improvement activities to increase the ability of the development process to fulfill quality requirements for the product or service being provided. automated data collection survey: An information gathering process that typically incorporates the use of vehicles fitted with equipment (e.g., lasers, high-speed cameras, and computers) specifically designed for collecting pavement and roadway features. automated data processing: A fully automated analysis process (i.e., no user interface) for profile data, collected images, and pattern recognition technology to assess pavement condition. bias: An error, constant in direction, that causes a measurement, or the mean of a distribution of measurements, to be offset from the true population mean (AASHTO 2006). blind site: A roadway segment for which condition data have typically been measured by agency or third-party personnel. calibration: A set of operations that establish under specified conditions the relationship between values of quantities indicated by a measuring instrument or measuring system, or between values represented by a material measure or a reference material, and the corresponding values realized by standards (AASHTO 2006). control site: A roadway segment for which condition data have typically been measured by agency or third-party personnel for use as a reference value. Data collected during the production phase are compared against the reference values to verify proper collection procedures and continued calibration of the equipment. In this way, control sites are used to assess the adequacy of the QC processes. corrective action: The improvements/adjustments to an organizationâs processes taken to eliminate causes of nonconformities or other undesirable situations. Specifically, they are actions to resolve discovered problems with calibration, defective equipment, data errors, or missing data. Glossary
94 Automated Pavement Condition Surveys crack measurement system: A system consisting of high-speed cameras, optics, and laser line projects to capture 2D images and 3D profiles. Used for automatic detection of cracks, macrotexture, and other surface features. cracking percent: asphalt pavementâthe percent of total wheel path area exhibiting all severity levels of fatigue type cracking; CRCPâthe percent of area exhibiting longitudinal cracking, punchouts, and patching; and JPCPâthe percent of slabs exhibiting transverse cracking, includes slabs with cracking that extends over the majority of its width (FHWA 2016). cross slope: The average transverse slope of the pavement surface, typically expressed in percent. data collection contractor: A private firm hired to collect, process, and deliver pavement condition data (and images) in accordance with the agency-specified scope of work. data quality management plan (DQMP): A document that specifies the data quality management procedures (including quality standards, QC, acceptance, corrective actions, and resources) that will be used and how the process will be implemented and assessed for effectiveness. distance measurement instrument (DMI): The onboard instrumentation and software used to determine the longitudinal distance that the measurement vehicle has traveled. faulting: The difference in elevation (i.e., vertical misalignment) across a concrete pavement joint or crack. geographic information system (GIS): A system for the management, display, and analysis of spatial information. geometrics: The positioning of the physical elements of the roadway that relate to operational quality and safety, described by parameters such as horizontal and vertical curves, tangents, radius of curvature, elevations, grades, lane dimensions, and cross slope. Global Positioning System (GPS): A satellite-based navigation system for determining user location on earth using a receiver. Highway Performance Monitoring System (HPMS): A national-level highway information system that includes data on the extent, condition, performance, use, and operating charac- teristics of the nationâs highways. independent verification: An unbiased and independent evaluation of data quality that is performed by someone other than the entity who collected or is receiving the data. International Roughness Index (IRI): A statistic used to estimate the amount of roughness in a measured longitudinal profile. The IRI is computed from a single longitudinal profile using a quarter-car simulation (AASHTO 2017b). linear reference system (LRS): A set of procedures for determining and retaining a record of specific points along a highway. Typical methods used are milepoint, milepost, reference point, and link-node (FHWA 2016). longitudinal grade: The slope (hilliness) of the pavement in the longitudinal direction (direction of travel) typically measured and expressed in percent. longitudinal profile: The vertical deviations of the pavement surface taken along a line in the direction of travel referenced to a horizontal datum. Long-Term Pavement Performance (LTPP): A large research project of in-service pavements to determine why pavements perform the way they do.
Glossary 95 mean profile depth (MPD): âThe measured profile is divided into segments having a length of 4 in. (100 mm). The slope of each segment is suppressed by subtracting a linear regression of the segment. This also provides a zero mean profile, i.e., the area above the reference height is equal to the area below it. The segment is then divided in half and the height of the highest peak in each half segment is determined. The average of these two peak heights is the mean segment depth. The average value of the mean segment depths for all segments making up the measured profile is reported as the MPD.â (ASTM 2015). National Highway System (NHS): This consists of roadways important to the nationâs economy, defense, and mobility. orientation system: A system that collects vehicle position, velocity, altitude, track, speed, and dynamics. pavement image: A representation of the pavement that describes a characteristic (grayscale, color, temperature, elevation, etc.) of a matrix of points (pixels) on the pavement surface. The images are used for the detection and extraction of pavement cracking data. percent within limits (PWL): The cumulative area under a normal distribution curve that represents the estimated percent of a population that falls above the lower specification limit, beneath the upper specification limit, or between the upper and lower specification limits. precision: The degree of agreement among a randomly selected series of measurements, or the degree to which tests or measurements on identical samples tend to produce the same results (AASHTO 2006). present serviceability rating (PSR): A mean rating of the serviceability of a pavement established by a rating panel under controlled conditions on a scale 0.1 to 5.0. profiler: A pavement profiling system that collects real-time, continuous measurements of longitudinal profile elevations, IRI, and faulting. quality: The degree of excellence of a product or service, the degree to which a product or service satisfies the needs of a specific customer, or the degree to which a product or service conforms to a given requirement (AASHTO R 10-06). quality control (QC): The activities needed to adjust production processes toward achieving the desired level of quality of pavement condition data (AASHTO R 10-06). quality standards: These define the resolution, accuracy, and repeatability that are used to determine the quality of each deliverable. radius of curvature: For a curve, it equals the radius of the circular arc that best approximates the curve at that point. reference value (ground truth): A value that serves as an agreed-upon reference for com- parison and is derived as a theoretical or established value, based on scientific principles, an assigned or certified value, based on experimental work of some national or international organization, or a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or engineering group (AASHTO R 10-06). repeatability: The comparison of repeated measurements of the same section under the same or similar conditions. The degree of variation among the results obtained by the same operator repeating a test on the same test section (adopted from AASHTO R 10). reproducibility: The degree of variation among the test results obtained by different operators performing the same test on the same material (AASHTO R 10-06).
96 Automated Pavement Condition Surveys resolution: The smallest increment that a characteristic measuring process must distinguish and display (ASTM 2012). For example, rut depth measured to the nearest inch (mm) or IRI measured to the nearest inch/mile (mm/km). road profile: The cross-sectional shape of the road surface in relation to the road corridor traversing the surrounding landscape. roadway segments: These are roadway sections from 1/100 mi to one mile long located in the driving lane. 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 2012). ROW image: A digital image record of the roadway right-of-way and adjacent visible sur- rounding area. rutting: The longitudinal surface depressions in the wheel path. A rut is more specifically defined as a broad longitudinal depression in the wheel path of the pavement surface with a depth of at least 0.080 in. (2.03 mm), a width of at least 1.0 ft (0.30 m), and a longitudinal length of at least 100 ft (30.5 m). smoothness: The measure of a pavementâs roughness reported as IRI. A statistic used to estimate the amount of roughness in a measured longitudinal profile. tolerance: The defined limits of allowable (acceptable) departure from the true value of a measured quantity. (ASTM 2012). transverse profile: The vertical deviations of the pavement surface from a level horizontal reference perpendicular to the lane direction of travel. validation: The mathematical comparison of two independently obtained sets of data (e.g., agency acceptance data vs. contractor data) to determine whether it can be assumed they came from the same population (AASHTO 2006). verification: See acceptance sampling and testing. verification sites: The collection of data by one or more devices during production data collection for confirming proper collection procedures, reproducibility, and continued calibration of the equipment. wheel path: A longitudinal strip of pavement 39 in. (1 m) wide. The inner edges of both wheel paths are offset from the center of the lane by 14.75 in. (0.375 m), and are therefore 29.5 in. (0.75 m) apart.