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Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports (2019)

Chapter: Chapter 4 - Uses of Pavement Condition Data

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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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Suggested Citation:"Chapter 4 - Uses of Pavement Condition Data." National Academies of Sciences, Engineering, and Medicine. 2019. Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25566.
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34 Uses of Pavement Condition Data The previous chapter discussed the different types of airport pavement condition or perfor- mance data that are commonly used to monitor airport pavement performance and to make decisions about pavement needs, as well as the different ways in which pavement condition data are collected. This chapter presents ways in which the collected data are used and identifies links between different needs for pavement condition data and the types of condition data that sup- port those needs. Needs vary depending on the type of project and the objectives of that effort. The following sections identify a number of different applications in which pavement condition data are used. For example, network-level pavement management is ideal for an agency with responsibilities over a system of airports, such as an aeronautics commission or department of transportation, or an individual airport interested in assessing the overall condition of the pavement network and estab- lishing rehabilitation priorities. A project-level assessment has a very different purpose, focusing on developing project needs and design recommendations to rehabilitate a pavement facility. As the objectives are quite different, the type and level of testing and evaluation would also be different. Compliance with FAA Regulations The FAA requires daily, regular, and monthly inspections that include pavement evaluations. FAA AC 150/5200-18 describes daily and weekly, monthly, or quarterly inspections to identify safety hazards, as well as the need for special inspections. This AC describes key features of a daily inspection performed on pavement areas, focusing on conditions that could contribute to FOD, unsafe aircraft operations, or drainage problems. Periodic inspections of pavements focus on rubber buildup, polishing, groove dimensions, or other factors affecting friction. Spe- cial inspections of pavements also consider safety factors, such as drainage, and the impact of ongoing construction activities on safe operations. Network-Level Management A traditional airport pavement management system (APMS) includes a network-level con- dition survey, whose results are used to develop a plan to address future pavement needs. A network-level APMS includes the following steps: • Establish a pavement inventory, • Assess existing pavement condition, • Estimate future pavement condition, and • Outline maintenance and rehabilitation needs and priorities. These steps are explained in greater detail in the following sections. C H A P T E R 4

Uses of Pavement Condition Data 35 Pavement Inventory One of the first steps in establishing an APMS is the conduct of a records review to determine the work history of the various pavement sections. In a pavement management database, the required information consists of the pavement type, year of construction or rehabilitation, and project limits. Other information, such as the type and thickness of pavement layers, the maintenance his- tory, and the sources of funding for the work can be entered into the database. Once populated, an airport will have access to the work history information for their entire pavement network in one convenient location. This information also serves as the building block for defining the network (consisting of branches, sections, and sample units) for a pavement management system. The presentation of this information can take several forms. Most pavement management programs have a default summary of work history that can be readily printed. An example of a “Work History Report” from PAVER, a commonly used pavement management software system developed by the U.S. Army Corps of Engineers, is shown in Figure 20. This informa- tion can also be presented in tabular or graphical/map format. Pavement Condition The determination of pavement condition is an essential component of any network-level pave- ment management program. In the airport community, the condition is generally collected and reported using the PCI procedure outlined in ASTM D5340, although other approaches are used. The PCI is reported at the section level and is commonly communicated in tabular or map for- mat. Figure 21 is an example of a PCI map at the section level. PCI results can also be rolled up to the branch level by computing area-weighted PCIs, although if the section-level results are highly variable, this will adversely affect the branch-level results. Evaluating reported PCIs is a quick and convenient way to compare the relative condition of individual pavement sections and is often a very significant input in determining the need for, and priority of, pavement rehabilitation. Although the PCI value is the most common metric evaluated, there are many other uses of the data collected during a PCI inspection. The determination of PCI requires investigation of seventeen different distress types for asphalt-surfaced pavements and sixteen different distress types for concrete-surfaced pavements (see Table 4). These detailed data are entered into the pave- ment management database and can be reported in various forms, such as the quantity of a certain distress type or distress type/severity combination on a given pavement section or branch. For network-level PCI inspections in which only a subset of the pavement area is inspected, the results reported for a section are an extrapolation of the distress quantity of the inspected area over the entire section area. For example, if 500 LF of medium-severity L&T cracking were identified over the inspected pavement area covering 25 percent of the total section area, the extrapolated quantity of distress would be 2,000 LF for the section. The quantity of distress at the branch level is com- puted as the sum of the extrapolated quantities from the individual sections. Table 9 shows data exported from PAVER presenting the quantity of each distress extrapolated to the section level. Pavement Deflection FWD testing is at times performed as part of network-level pavement management studies. Advantages of this practice include the ability to accomplish the following: • Evaluate material properties and overall pavement structural condition; • Assess structural capacity (e.g., PCN, load limits, remaining life), which are additional inputs into setting rehabilitation priorities; and • Refine the type of rehabilitation needed (repair, overlay, or reconstruction). Such testing should not be considered a replacement for project-level investigation prior to construction.

36 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports An APMS update is often the ideal time to assess the pavement’s structural capacity or determine PCNs. Information required for analysis is typically gathered for a PMP update. Although the FAA only requires analysis of runways for Part 139 airports serving aircraft over 12,500 pounds and Grant Assurance compliance, in accordance with ICAO requirements, it is generally good practice to determine the PCN of the entire airfield, as aircraft must get from runways to aprons and back again. Strategic-Level Management Strategic decision making may occur without any consideration of pavement conditions. Such strategic-level management might focus on capacity, growth, market shifts, and so on. In some cases, however, it is expected that strategic management (not considering capacity) Figure 20. Work History Report from PAVER.

Figure 21. Sample PCI map (PCI values are shown in parentheses).

38 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports would make use of data developed as part of network-level pavement management and may be performed either as part of that network-level activity or separately. The data collected and analyzed as part of a network-level project are typically used to develop a CIP or M&R plans for maintaining the airport pavement network over the next 5 to 10 years. The extent of the strategic plan is a result of the plan duration. For example, if an agency develops a 3-year CIP, the extent may be limited to a few facilities, while a 15-year CIP may include half of an airport. The presentation of pavement performance data (such as in the form of PCIs) is at the heart of most strategic analyses. Strategic management often occurs in two phases. The first phase is initial planning, which is primarily based on pave- ment data and may not be realistic to implement because of funding, operational, or capacity constraints. The second phase, strategic plan finalization, can vary significantly between agen- cies, but it will often take into account additional factors and input from multiple stakeholders, such as airlines, tenants, users, engineering, maintenance, operations, planning, and the FAA. Initial Strategic Planning The initial strategic planning focuses on pavement data and is based on engineering judgment. This process is carried out by consultants or engineering departments. Pavement management Branch Section PCI Area, SF Description Severity Qty Qty Units Deduct Value APPARK APPARK-01 46 38,400 ASR L 15 Slabs 10.7 ASR M 2 Slabs 6.6 CORNER BREAK L 1 Slabs 0.8 CORNER SPALL L 1 Slabs 0.5 FAULTING L 3 Slabs 3.0 JOINT SPALL L 1 Slabs 0.4 JT SEAL DMG M 80 Slabs 7.0 JT SEAL DMG H 16 Slabs 12.0 LARGE PATCH L 44 Slabs 17.3 LARGE PATCH M 12 Slabs 19.3 LINEAR CR L 6 Slabs 5.8 LINEAR CR M 2 Slabs 5.1 SCALING M 1 Slabs 0.9 SHRINKAGE CR N 31 Slabs 4.5 SMALL PATCH L 11 Slabs 1.9 SMALL PATCH M 3 Slabs 2.0 APPARK-02 33 27,675 ALLIGATOR CR L 140 SF 14.6 ALLIGATOR CR M 2,164 SF 53.0 ALLIGATOR CR H 133 SF 29.4 L&T CR L 237 FT 4.8 L&T CR M 81 FT 6.7 PATCHING L 3,099 SF 15.4 PATCHING M 161 SF 8.2 RUTTING L 172 SF 13.4 RUTTING M 2 SF 13.0 SWELLING L 81 SF 1.6 WEATHERING L 12,299 SF 4.5 WEATHERING M 12,116 SF 14.2 Note: JT= joint, DMG = damage, CR = cracking. Table 9. Extrapolated distress quantities from PAVER report.

Uses of Pavement Condition Data 39 Figure 22. Impact of different budget scenarios on PCI. software is used to identify pavements in need of repair or rehabilitation. Pavement manage- ment software have robust capabilities for using PCI data. The ability to analyze and develop pavement performance models that predict the future PCI is essential to the assessment of future capital needs. Through the entry of unit costs for such activities, pavement management soft- ware are capable of evaluating various budget scenarios to determine the predicted outcome over a specified timeframe (in terms of PCI of individual pavement sections and the network as a whole). In this manner, the impact on PCI of different financial expenditures (and the impact of not funding any rehabilitation) can be evaluated. In Figure 22 various budget scenarios are com- pared over a 10-year period by illustrating the impact of the budget on the resultant network- wide PCI. With such an illustration, it is easy to gauge the impact of different budget scenarios. Some airports take the analysis to another level by defining pavement assets at the slab or sample unit level. This is a more time intensive and data-driven approach, but the ability to pinpoint and address problems can be greatly enhanced with such a system. However, it requires ample resources to establish and maintain such a system and is typically only used at medium- and large-hub airports. While the analysis capabilities of available pavement management software are powerful, there are many other variables that must be considered to develop the most effective plan for an airport. Other factors that need to be considered include the structural condition and how the existing pavement condition will impact potential rehabilitation options. Such considerations are critical to ensure that the rehabilitated pavement will provide the desired service life. Input from other stakeholders should also be accounted for in terms of the future plans of the airport and how the various pavement facilities will be used. Operational considerations, such as what areas will remain usable during a pavement closure, may also affect pavement decisions. Even if a pavement is not triggered for M&R by its condition, work may be undertaken because it is adjacent to sections that will be treated. An airport’s Master Plan must also be considered; the CIP should reflect what is already incorporated into the airport’s plans for its infrastructure. Such unique factors are critical to development of an effective CIP, but cannot be modeled in pavement management software. CIPs are often presented in tabular or map format. Table 10 shows an example of a CIP pre- sentation. The type of rehabilitation, timing, and cost of each rehabilitation project are essential pieces of information for an effective plan. The creation of a CIP map, such as shown in Figure 23,

40 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports Year Branch Section 2015 PCI PCI Before Project Estimated Costs Rehabilitation Method 2016 TU 26 66 65 $861,000 Mill and overlay with repairs30 19 14 R1129 10C 54 52 $2,533,000 Mill and overlay 20C 37 33 26C 37 33 30C 36 32 40C 70 68 42C 61 60 47C 33 29 50C 48 46 60C 27 23 70C 41 39 R17R35L 19C 91 86 $2,335,000 Mill and overlay 21C 90 86 22C 34 30 23C 90 86 24C 43 39 26C 39 37 28C 51 48 30C 53 51 40C 70 68 50C 70 68 55C 36 32 60C 58 57 62C 55 53 64C 56 54 66C 84 80 70C 60 58 TG 10 36 34 $323,000 Mill and overlayR1129 50NE 60 58 50SW 49 47 60F 61 60 60NE 65 64 60SW 60 59 70NE 55 53 70SW 54 52 2016 Subtotal: $6,052,000 2017 TA 80 50 46 $4,702,000 Mill and overlay with repairs90 29 20 94 53 50 95 89 82 Mill and overlay 100 31 30 PCC reconstruction AI 10 51 49 $669,000 Slab replacements (23 slabs) 20 66 63 30 31 30 40 45 43 50 45 43 55 84 80 60 44 43 R17R35L 18C 62 58 $685,000 Mill and overlay20C 27 24 2017 Subtotal: $6,056,000 Table 10. Sample CIP and associated costs in tabular format.

Uses of Pavement Condition Data 41 Year Branch Section 2015 PCI PCI Before Project Estimated Costs Rehabilitation Method 2018 TJ 40 50 49 $766,000 Slab replacements (30 slabs) AV 13 17 6 $459,000 Mill and overlay30 0 0 PCC reconstruction TC 10 61 54 $1,846,000 Mill and overlay 20 53 46 30 46 40 30FW 54 47 30FE 54 47 35 58 51 35FE 65 58 35FW 65 58 TF 10 55 48 $75,000 Mill and overlay R1129 90SW 47 41 $286,000 Mill and overlay90C 53 47 90NE 53 47 TU 50 54 47 $126,000 Mill and overlay TYB 34 22 6 $141,000 Mill and overlay with repairs TA 30 53 48 $126,000 Mill and overlay40 61 59 AVI 50 34 33 $542,000 Portland cement concrete (PCC) reconstruction190 37 36 TP 35 24 8 $144,000 Mill and overlay TJ2 10 56 49 $454,000 Mill and overlay 2018 Subtotal: $4,965,000 2019 TC1 10 60 57 $1,240,000 PCC reconstruction TC3 10 57 55 $1,036,000 PCC reconstruction THD 10 61 58 $657,000 Slab replacements (25 slabs) TGB 10 57 47 $454,000 Reconstruction TA3 05N 70 67 $281,000 Mill and overlay with repairs10N 55 4910S 58 54 TWESTJET 10 51 49 $263,000 Slab replacements (10 slabs) R0826 10 64 55 $1,191,000 Mill and overlay20 63 61 TL 10 59 56 $173,000 Mill and overlay 2019 Subtotal: $5,295,000 2020 R17R35L 10C 45 40 $14,503,000 Reconstruction 10W 81 76 10E 62 57 05E 43 34 18C 62 92 20C 27 20 20W 47 28 20E 53 37 TA 10 66 62 $780,000 Reconstruction TC 10 61 94 $544,000 Reconstruction 2020 Subtotal: $15,827,000 2016-2020 Total: $38,195,000 Table 10. (Continued).

Figure 23. Sample CIP in map format.

Uses of Pavement Condition Data 43 is a quick visual method of displaying the recommendations. Rather than specifying the timing (year) in which a rehabilitation project should be performed, some airports elect to identify projects in terms of priorities, which allows them to tackle the highest priority project as fund- ing becomes available. Strategic Plan Finalization Ultimately, there are many factors that affect pavement M&R decisions, but economic fac- tors may be the driving force. Because of the importance of available funding, the cost of rec- ommended maintenance, repair, or rehabilitation actions must be developed. After the initial strategic plan is created, it will be reviewed and modified before implementation. There may be multiple revisions of the strategic plan depending on what input is received from stakeholders. Figure 24 illustrates a process for developing a strategic plan (again, not considering big-picture issues such as capacity). Each agency will modify this process slightly depending on its organi- zational structure and funding sources. In some instances, consultants or others will assume the same role assigned to an airport’s department or committee. Typically, planning and engineering departments (or consultants playing those roles in some cases) will review the initial strategic plan internally before sharing with other stakeholders. During this process, they decide how extensively a strategic plan will be presented to other stakeholders. Engineering departments may remove certain pavements from strategic planning because the condition of those pavements is not a high priority and funding is limited. Engineer- ing and planning personnel will also take into account additional factors such as facility use, planned non-pavement projects, the Master Plan, and internal goals and apply their experi- ence to modify the strategic plan. For example, the decision to postpone the rehabilitation of a runway to coincide with a project to upgrade lighting would be made at this stage. Engineering departments will perform an in depth review of the pavement data or visit each location with the intent to verify rehabilitation is necessary or determine the rehabilitation method. A detailed cost estimate may be developed at this time, or it may be delayed until after the strategic plan is reviewed by maintenance and operations personnel. The review by maintenance and operations personnel is suggested, as maintenance and operations staff spend significant portions of their time on the airfield and can provide insight into the state of the airport pave- ment or operational considerations that may impact the sequence or completion of planned work. These reviews may include studying a PCI map or making a site visit to examine pave- ments. The experience and opinions of maintenance and operations personnel can be vital to project prioritization. Often after this, an updated version of the strategic plan will be submitted to a combination of financial committees, other advisory committees, and directors. These stakeholders help shape the pavement strategic plan into the greater vision of the airport. These stakeholders may have their own opinions about certain projects or insight into which projects are likely to receive funding. They may also provide feedback about the timing of projects. For example, the fund- ing requirements for pavement projects may be balanced between years; however, pavement projects may need to be shifted to balance funding requirements for the entire airport or agency. Next, projects from the strategic plan will be submitted to state and local governmental agen- cies as well as the FAA. These organizations will provide feedback and ultimately decide which projects receive funding. Typically, the need for each project must be justified at this stage. In most cases these organizations are responsible for ensuring funds are spent on meaningful projects. Many agencies revisit their strategic plan every year. Pavement data may not be collected between strategic plan updates; however, condition projections will be used to account for

44 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports © 2018 Applied Pavement Technology Figure 24. Outline of the activity flow for development of a strategic plan.

Uses of Pavement Condition Data 45 deterioration. Strategic plan reviews address projects that have been funded, changes or desired changes in use, and other factors that affect strategic planning. Although strategic plans rely on technical analysis and decision making, communication is also vital. An effective strategic plan is the result of frequent communication between stake- holders. A strategic plan that is created within a silo will not be beneficial to the airport as a whole. The creation and update of the strategic plan compels stakeholders to build and nurture relationships between departments and agencies. Project-Level Assessment A project-level assessment is highly recommended prior to rehabilitation or reconstruc- tion, particularly for any project other than a small, routine rehabilitation effort. It considers different strategies or treatments and the development of a detailed design for the selected treatment(s). While many of the components are the same as a network-level management, the extent and manner in which the assessments are conducted can vary significantly because the objectives of the two types of study are quite different. For example, project-level condition surveys typically use a much larger sample size than network-level surveys, up to 100 percent. Pavement Condition/Distress Mapping As the purpose of project-level pavement condition inspections is quite different from network-level surveys, the approach should be tailored as well. In addition to identifying the exhibited distresses, in a project-level investigation it is also important to determine the cause of the distress or deterioration so that the rehabilitation option can be designed to address the issue. A thin overlay would not be a good option for an existing asphalt-surfaced pave- ment with widespread rutting and alligator cracking, as the root cause of the problem would not be addressed and such an overlay is unlikely to perform very well. Likewise, a concrete- surfaced pavement with extensive D-cracking would not be a good candidate for partial-depth patching. The type and extent of inspection will vary and could be more or less intensive depending on the pavement condition. If the pavement is badly deteriorated, such as exhibiting exten- sive materials-related distress, and reconstruction has been predetermined as the only viable solution, a detailed pavement condition inspection showing what is already known does not make a lot of sense. For a reconstruction candidate, the following evaluation methods should be explored: • Subgrade evaluation to determine design inputs for reconstruction and • Possible drainage investigation. On the other hand, if maintenance and repair is a feasible option, then a more detailed inspec- tion identifying the specific distresses (such as through a complete distress mapping) will provide the information needed to develop accurate maintenance and repair plans. For a rehabilitation candidate, the following evaluation methods should be explored: • Detailed distress survey, • Nondestructive evaluation of structural capacity, • Subgrade evaluation to determine design inputs for rehabilitation, • Coring, and • Possible drainage investigation. Besides evaluating surface distress through a visual pavement condition, it is also advisable to examine other characteristics that could impact the rehabilitation recommendations, such as

46 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports the drainage conditions (or evidence of moisture damage), the cross slopes, shoulder condition, condition/dimensions of grooves, and subgrade stability. A thorough evaluation for condition survey results may also indicate the need for additional data collection, such as nondestructive testing or coring. All of these factors need to be collectively considered to determine the best rehabilitation option. Pavement Deflection Deflection testing is highly encouraged for most project-level assessments, as it provides an examination of the pavement structure beyond that provided in a visual evaluation of the pave- ment surface. A well designed and executed deflection testing program can be used to assess the following conditions: • Pavement response to loading (normalized deflections), • Subgrade support conditions [subgrade modulus, California bearing ratio (CBR), or k-value], • Material layer properties (elastic modulus), • Variability in one or more layers of the pavement system, • Localized areas of weakness, • Structural capacity/remaining life, and • Load transfer on jointed concrete pavements. AC 150/5370-11B, Use of Nondestructive Testing in the Evaluation of Airport Pavements, provides extensive information on nondestructive techniques and applicability, as well as details regarding testing for specific project applications. As noted elsewhere, more extensive testing is appropriate for a project-level application compared to a network-level assessment. Table 11 shows the FAA recommendations for the frequency of testing to be performed for project-level and network-level investigations. Network-level testing is also performed in Test Type Jointed PCC and HMA Overlaid PCC HMA Project Level Network Level Project Level Network Level Offset ft (m) Spacing ft (m) Offset ft (m) Spacing ft (m) Offset ft (m) Spacing ft (m) Offset ft (m) Spacing ft (m) Center 10 (3) 30 (9) 65 (20) 100 (30) 100-200 (30-60) 400 (120) 10 (3) 200-400(60-120) 200-400 (60-120) 100 (30) 100-200 (30-60) 200-400 60 (120) 10 (3) 200-400(60-120) Transverse Joint 10 (3) 30 (9) 65 (20) 100-200 (30-60) 200-400 (60-120) 400 (120) 10 (3) Longitudinal Joint 20 (6) 40 (12) 60 (18) 200 (60) 400 (120) 400 (120) Corner 20 (6) 40 (12) 60 (18) 200 (60) 400 (120) 400 (120) Note: For each centerline offset, there are two nondestructive testing (NDT) passes, one to the left and one to the right; spacing is staggered between adjacent NDT passes; and a minimum of two NDT tests should be conducted per pavement section (HMA = hot-mix asphalt). Table 11. FWD minimum runway and taxiway test locations and spacings (AC 150/5370-11).

Uses of Pavement Condition Data 47 two testing lanes within the keel (loaded) portion of the runway or taxiway, while six lanes of testing are recommended for project-level testing. In addition to the frequency differences, testing at other locations, such as at longitudinal joints and slab corners, is prescribed for project-level testing. The results of FWD testing are often presented in profile plots of the evaluated property over the length (or station) of the facility. Figure 25 is an example of a profile plot show- ing the subgrade modulus back-calculated from pavement deflections. This type of exhibit is ideal for examining the results as a whole and for evaluating the relative difference in a pavement property across a facility. This plot was generated from six passes of the equipment at different offsets on either side of the pavement centerline. Pavement sections are also shown, and from this plot (and others like it, showing pavement layer moduli, for example) it is possible to view relationships between the deflection data and pavement properties used in new or rehabilitation design. A change in the property can indicate a change in the pave- ment cross section, a change in the subgrade support conditions (such as transition from a cut to a fill section), or a change in the condition/performance of the pavement. By evaluating charts such as this one it is possible to see trends in the data and how one property can affect others. By examining these additional properties and parameters, the designer can develop a better solution for specific site conditions. Studying this information can also help to minimize the risk of premature failure by identifying widespread or localized structural concerns in advance and addressing them in the pavement design. Figure 25. Profile plots of FWD testing results.

48 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports Maintenance and Repair Plans Maintenance and repair plans identify the type, quantity, and, in some cases, location of the recommended maintenance and repair activities. They are prepared as part of a network-level or project-level survey and are primarily based on pavement distresses. As previously noted, network-level surveys in which a sampling of the pavement area is inspected can be used to gen- erate estimates of distress and associated maintenance and repair needs. While such estimates are adequate for some projects, they have several limitations. The accuracy of the repair quantities is tied to the consistency of the pavement condition and the extrapolation of the pavement distress from the inspected area to the total pavement area. In addition, general assumptions have to be made about the repair dimensions in relation to the distress measurement. For HMA pavements in which distresses are measured in length or area, an additional quantity of say 10 percent can be added as the repair dimension. For concrete pavements in which distresses are only noted as being present on a slab, the determination of an accurate repair quantity can be more problematic, especially for addressing a distress like D-cracking, which is generally more extensive at the bottom of the slab. Finally, the location of the required maintenance and repair activities is not specified in a conventional PCI survey (although they can be in certain manual or automated distress mapping approaches); only the quantity over an entire section area can be determined from a network-level survey. Where detailed plans are needed for repair by internal maintenance forces or for contractor bid- ding and execution (or in any situation where the accuracy of the repair quantities and/or location of specific repairs is needed), distress mapping is suggested (as shown in Figure 1, for example). If only repair areas are needed, then only the distresses requiring repair need to be mapped. In most cases, however, a network-level pavement condition inspection will still be required to determine the PCI. When the pavement distresses are mapped over the entire pavement area, both purposes are served. The mapped distress can be used to generate maintenance and repair plans, while the individual distresses can be tied to a branch, section, and sample unit and imported into a pave- ment management database such as PAVER or PAVEAIR (which the FAA hosts). A geographic information system (GIS) application is ideal for managing these data, and, with some simple programming, can be used to pull the required data into the pavement management database to determine PCIs and perform further analyses. Troubleshooting and Forensic Investigations Special investigations are conducted to examine the cause of poor pavement performance and to identify solutions. A forensic investigation may take many forms, and in addition to the distress data generated from a PCI survey, may include deflections, other measures of surface conditions, and the results of many different types of subsurface investigations (e.g., material type, layer thickness, bonding conditions, stripping, presence of moisture, material properties). There is not a one-size-fits-all approach when it comes to forensic investigations. It is important to have a lead investigator who is experienced with airport pavement design and performance to grasp the prob- lem and recommend the appropriate tests to validate or refute the hypothesis. In some cases, it is also necessary to bring in experts on a particular subject (such as asphalt or concrete mix design). Communication of Conditions and Plans to Stakeholders Pavement conditions may be communicated to external or semi-external parties to explain actions or solicit support. This communication is likely to include descriptive summaries of conditions or graphical representations of current or projected conditions that are similar to what are found at the network and strategic levels.

Uses of Pavement Condition Data 49 Stakeholders can include airlines, tenants, users, engineering, maintenance, operations, plan- ning, and the FAA. Stakeholders are generally interested in a higher-level overview of the results and recommendations, as well as the impact of spending or not spending funds to address pavement-related needs. The following are sample questions stakeholders might ask: • What is the impact on the pavement network (such as the area-weighted PCI) if $2 million is spent annually on capital projects over the next 5 years? • What benefit can be gained over the long term by applying pavement maintenance and pres- ervation treatments now? • What is the projected PCI over the next 10 years if no rehabilitation work is performed? (Table 12 is an example of a response to this question, showing the projected PCI by year as well as the functional remaining life, or the number of years until the pavement’s functional performance reaches a trigger value.) Such questions can be answered through an analysis of data collected as part of a network- level pavement management study. The results of such scenarios can help guide or influence stakeholders to provide funds for needed projects, understanding that the costs will be multi- plied if a project is delayed. Another consideration that stakeholders must take into account is risk, which is often an over- looked factor in pavement management studies. What is the risk of FOD and potential damage to aircraft if a repair or rehabilitation project is not funded? What is the financial risk of delay- ing a rehabilitation project for a number of years? The answers to these questions, although exceedingly difficult to quantify, help guide decisions from stakeholders by illustrating not only the impact of the proposed project but also the impact of not doing that project. This type of information is best displayed in an executive-level report or presentation that conveys the results and recommendations without becoming too detailed. Stakeholders need the information at their fingertips to make decisions, and it is unrealistic to expect these parties Branch ID Section ID Projected PCI by Year Functional Remaining Life20 17 20 18 20 19 20 20 20 21 20 22 20 23 20 24 20 25 20 26 20 27 RW0826 01 89 87 84 82 80 78 76 75 73 72 70 > 10 years 02 89 87 84 82 80 78 76 75 73 72 70 > 10 years 03 92 89 86 84 82 80 78 76 74 73 71 > 10 years 04 97 93 90 88 85 83 81 79 77 75 74 > 10 years 05 98 95 92 89 87 84 82 80 78 76 75 > 10 years TWA 01 99 98 97 97 96 95 94 93 93 92 91 > 10 years 02 98 94 91 89 86 84 82 79 78 76 74 > 10 years 03 88 84 80 77 74 71 68 65 63 61 59 > 10 years 04 92 89 86 84 82 80 78 76 74 73 71 > 10 years 05 98 95 92 89 87 84 82 80 78 76 75 > 10 years TWB 01 98 97 95 93 91 90 88 86 84 82 80 > 10 years02 85 83 81 79 77 75 72 70 68 65 63 > 10 years AGA 01 30 27 24 21 18 15 12 10 8 6 3 0 years 02 41 38 35 32 28 25 22 19 16 13 11 1 year 03 61 60 59 57 56 54 52 50 48 45 43 > 10 years 04 51 48 45 42 40 37 34 31 29 26 23 5 years 05 41 38 35 32 30 27 24 22 19 16 13 1 year 06 82 78 75 72 70 68 66 65 63 62 61 > 10 years ATERM 01 63 61 60 59 57 56 54 52 50 47 45 > 10 years02 77 74 71 69 67 66 64 63 61 60 59 > 10 years Table 12. 10-year PCI projections and functional remaining life.

50 Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports to read through a bulky report or decipher the information from a pavement management database. Summary This chapter summarized different uses for pavement condition data. Network-level uses are commonly associated with pavement management and can include pavement condition data as well as other data to support network-level decisions. At the strategic level, pavement condi- tion data are used for planning purposes, such as the development of a CIP. Pavement condition data are used at the project level to determine what treatment strategy is appropriate as well as to design that strategy. The types and amount of data used for project-level decisions are typically greater than those associated with the network- or strategic-level uses. These other uses for pavement condition data are identified as follows: • Developing maintenance and repair plans, • Complying with FAA regulations, • Communicating with stakeholders, and • Troubleshooting and forensic investigations. The same types of data can help to address many different needs. Where differences emerge is in the quantity of data collected and how those data are analyzed and communicated to end users.

Next: Chapter 5 - Shared Uses and Presentation of Condition Data »
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“Pavement condition data” are essential inputs to the process of managing airport pavements and ensuring safe operations. The technology available today to collect pavement condition data is considerably different from that available even 20 years ago, and new technologies are being developed and introduced into practice at a rapid pace.

ACRP Research Report 203: Guidelines for Collecting, Applying, and Maintaining Pavement Condition Data at Airports provides guidance on the collection, use, maintenance, and application of pavement condition data at airports. Such data include conditions that are visually observed as well as those that are obtained by mechanical measurement or other means. Visually observed distresses on a pavement surface (such as cracking, rutting, patching, and spalling) are widely used and accepted as indicators of pavement performance.

A key part of the background study leading to this report was the development of case studies of seven airports or airport agencies on their experiences with pavement data collection, use, and management. They include: Houston Airport System (Houston, Texas), Salt Lake City Department of Airports (Salt Lake City, Utah), Dublin International (Dublin, Ireland), Columbus Regional Port Authority (Columbus, Ohio), Gerald R. Ford International Airport Authority (Grand Rapids, Michigan), North Dakota (statewide), and Missouri (statewide).

Additional Resources:

  • An Appendix with case studies of airports and agencies based on responses to the project survey, the experience of the project team, and input from the ACRP project panel.
  • This presentation template is based on the content of ACRP Research Report 203. It provides information on airport pavement condition data collection, use, and storage that can be customized by a presenter to cover a subset of the overall ACRP report.
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