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98 Aircraft Classification Number (ACN): A numerical expression of the relative effect of an air- craft of a given configuration on a pavement structure for a specified standard subgrade strength. ACNs are a standard created by the International Civil Aviation Organization. Backlog: Necessary pavement work that has not been completed and therefore remains to be done 1 or more years after the need for it was first identified. Branch: A readily identifiable part of a pavement network that has a distinct function. For example, a runway or apron is a distinct branch in a pavement network. Capital Improvement Program (CIP): A detailed rehabilitation program spanning a specified time period. CIPs are intended to present a cost-effective planning schedule that, if carried out, will keep the pavement network at a targeted level of performance. Continuous friction measurement equipment (CFME): A family of devices used to calculate the friction or skid resistance of a pavement. CFME is typically used on runways and high- speed taxiways. Distance measuring instrument (DMI): A device installed in ground-based vehicles to deter- mine distances/locations of collected data. Falling weight deflectometer (FWD): A device designed to impart to the pavement an impulse load similar in magnitude and duration to that of a moving aircraft and measure the deflection response of the pavement to that load. An FWD is composed of a load plate through which a dropped mass delivers a load to the pavement, while individual geophones located at the bottom of the load plate and at specified distances away from the load plate measure the pave- ment response to the load. Flexible pavement: Pavement consisting of a bituminous or hot-mix asphalt surface, which deflects under loads to distribute loads through the base and subgrade layers. Geographic information system (GIS): A computerized database that defines the specific locations of various attributes, features, or data items on a coordinate basis. Global positioning system (GPS): A system of satellites, computers, and receivers that is able to determine the latitude and longitude of a receiver on Earth. Heavy FWD (HWD): A type of FWD that can generate a maximum dynamic load of 54,000 pounds, rather than the maximum dynamic load of 34,000 pounds generated by an FWD. The larger loads are used for pavements with thicker cross sections. Large hub: A commercial service airport carrying one or more percent of the U.S. annual passenger boardings. Glossary
Glossary 99 Light detection and ranging (LiDAR): A system of lasers and sensors supported by traditional cameras, GPS receivers, and DMIs used to generate 360-degree point-cloud images of the pave- ment and surrounding facilities that allow the identification and analysis of pavement distresses as well other facilities included in an asset management system. Load transfer efficiency (LTE): A percentage that describes the distribution of loads across dis- continuities in concrete pavements such as cracks or joints. LTE is calculated as the percentage of the deflection of the approaching slab divided by the deflection of the leaving slab when a load is applied. Longitudinal profile: The measure of the deviations in the elevation of the pavement surface in the longitudinal direction, related to or sometimes referred to as pavement smoothness or roughness. Macrotexture: Irregularities on the pavement surface that deviate from a perfectly flat surface with the texture wavelength, or distance between peaks, measuring between 0.02 and 1.97 inches. Macrotexture is present between aggregates at the surface of the pavement. Medium hub: A commercial service airport with between 0.25 and 1 percent of the U.S. annual passenger boardings. Megatexture: Irregularities on the pavement surface that deviate from a perfectly flat surface with the texture wavelength, or distance between peaks, measuring between 1.97 and 19.69 inches. Megatexture can be recognized in the smoothness of the pavement surface and is often caused by deterioration in the pavement. Microtexture: Irregularities on the aggregate surface with the texture wavelength, or distance between peaks, measuring less than 0.02 inches. Microtexture is a key factor in the skid resistance characteristics of a pavement. Mobile mapping system (MMS): A system that collects geospatial data to provide geo-referencing to other data collected by a ground-based vehicle. Network: A group of pavements that will usually be managed together by an airport or agency. Network-level: A project that would include evaluation of a majority or all pavements managed by an airport or agency. The development of a multi-year CIP is an example of network-level airport activity. 95 percent confidence level: A statistical term for the probability that a new data point in a selected population would fall between a specified range of values. The number of samples inspected in a pavement section can be adjusted up or down the total number of samples in the section and the standard deviation between those samples to meet a 95 percent confidence level in the sectionâs PCI. Nondestructive testing (NDT): A variety of technologies and techniques used to evaluate material properties without causing damage to the pavement system. Typical NDT for airfields can include tests to measure deflections with FWD or HWD equipment, tests to measure surface friction with CFME, tests to measure roughness using a non-contact profiler, or tests to produce images of the subsurface using ground penetrating radar. Pavement classification number (PCN): A number that expresses the load-carrying capacity of a pavement for unrestricted operations. PCNs are a standard created by the International Civil Aviation Organization. The PCN of a pavement is reported as a whole number indicating the load-carrying capacity, followed by either an R or an F to indicate if the pavement is rigid or flexible, followed by a letter of A, B, C, or D indicating the strength of the subgrade, and a third letter of W, X, Y, or Z indicating the maximum tire pressure supported by the pavement.
100 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports Pavement deflection: The change in pavement surface elevation to an applied load. The deflec- tion of a pavement surface is used to calculate the structural layer stiffness and subgrade resilient modulus for a pavement. Pavement condition index (PCI): A numerical indicator between 0 and 100 that reflects the surface functional condition of the pavement. Pavement maintenance: Any preventive and regular or recurring work necessary to preserve existing pavements. Pavement maintenance can typically include crack or joint sealing, patching placed to repair distresses, or the placement of surface treatments. Pavement management program (PMP): A wide spectrum of activities, including the planning and programming of investments, design, construction, maintenance, and the periodic evalua- tion of performance, used to provide a cost-effective and efficient pavement network. Pavement preservation: A program employing a network-level, long-term strategy that enhances pavement performance by using an integrated, cost-effective set of practices that extends pavement life and improves safety. A pavement preservation program typically consists of preventive maintenance, minor rehabilitation (nonstructural), and some routine maintenance. Pavement reconstruction: The replacement of a pavement structure after the removal or recycling of an existing pavement structure. Pavement rehabilitation: Structural enhancements completed on a pavement system to extend the service life of an existing pavement and/or improve its load-carrying capacity. Typical pave- ment rehabilitation methods often include placing an asphalt overlay, possibly after the cold milling of a surface, or crack, seating, or rubblization of a concrete pavement. Project-level: Actions carried out over a small area or number of sections within a pavement network, possibly including distress inspections, PCI calculations, NDT, or the collection and evaluation of cores. Investigating pavement conditions on a single runway in order to decide between different rehabilitation or reconstruction methods or to design rehabilitation or recon- struction methods is an example of project-level actions. Right-of-way (ROW) cameras: Cameras on a ground-based vehicle positioned to take images of pavement and surrounding features. Rigid pavement: Pavement composed of a concrete with sufficient strength to resist deflection from loads and instead distribute the load over relatively wide areas of base or subgrade layers. Sample unit: A subdivision of a pavement section for PCI inspection purposes. A sample unit for a runway, taxiway, or apron pavement consists of 20 Â± 8 slabs for concrete-surfaced pavements and 5,000 Â± 2,000 square feet for asphalt-surfaced pavements. Section: The smallest management unit when considering the application of M&R. Factors to consider when dividing a branch into sections include pavement structure, traffic, construc- tion history, pavement rank (or functional classification), drainage facilities and shoulders, and condition. Skid resistance: The ability of the traveled surface to prevent the loss of tire traction. To have good skid resistance, pavements need good macrotexture to provide paths for water to escape and good microtexture to provide a degree of sharpness necessary for the tire to break through the residual water film. Small hub: A commercial service airport with between 0.05 and 0.25 percent of the U.S. annual passenger boardings. Stopgap: Maintenance completed as a temporary solution to repair distresses that pose safety concerns.
Glossary 101 Structural capacity: The load-carrying capacity of a pavement that can be determined through an in-depth evaluation of the material layers and thickness within a pavement structure and/or through an evaluation of the surface deflections. Structural condition index (SCI): A PCI calculated only from the procedureâs structural dis- tresses. The SCI is used in the FAAâs pavement rehabilitation design procedure to characterize the condition of an existing pavement prior to overlay. Pavement friction: The force that resists the relative motion between a vehicle tire and a pave- ment surface. Three-dimensional (3D) laser imaging: A system of laser scanners supported by traditional cameras, GPS receivers, and DMIs used to generate 3D images of the pavement surface that allow the identification and analysis of pavement distresses. Trigger: A level of pavement performance at which the need for maintenance, rehabilitation, or reconstruction is needed. Unmanned aerial system (UAS) or small unmanned aerial system (sUAS) or unmanned aerial vehicle (UAV): Commonly referred to as drones, these are aircraft controlled remotely without a human, onboard pilot. These systems can be fitted with imaging equipment such as cameras, LiDAR, or 3D laser imaging to take detailed aerial images that can be analyzed to evalu- ate distresses.