National Academies Press: OpenBook

Common Airport Pavement Maintenance Practices (2011)

Chapter: Chapter Five - Identification of Needs

« Previous: Chapter Four - Technology of Pavement Preservation Treatments
Page 21
Suggested Citation:"Chapter Five - Identification of Needs." National Academies of Sciences, Engineering, and Medicine. 2011. Common Airport Pavement Maintenance Practices. Washington, DC: The National Academies Press. doi: 10.17226/14500.
×
Page 21
Page 22
Suggested Citation:"Chapter Five - Identification of Needs." National Academies of Sciences, Engineering, and Medicine. 2011. Common Airport Pavement Maintenance Practices. Washington, DC: The National Academies Press. doi: 10.17226/14500.
×
Page 22
Page 23
Suggested Citation:"Chapter Five - Identification of Needs." National Academies of Sciences, Engineering, and Medicine. 2011. Common Airport Pavement Maintenance Practices. Washington, DC: The National Academies Press. doi: 10.17226/14500.
×
Page 23
Page 24
Suggested Citation:"Chapter Five - Identification of Needs." National Academies of Sciences, Engineering, and Medicine. 2011. Common Airport Pavement Maintenance Practices. Washington, DC: The National Academies Press. doi: 10.17226/14500.
×
Page 24
Page 25
Suggested Citation:"Chapter Five - Identification of Needs." National Academies of Sciences, Engineering, and Medicine. 2011. Common Airport Pavement Maintenance Practices. Washington, DC: The National Academies Press. doi: 10.17226/14500.
×
Page 25

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

The identification of pavement preservation needs described in this chapter is based on the results of pavement condition surveys, the prediction of pavement deterioration, and the desirable level of service for airfield pavements (Unified Facilities Criteria on Pavement Maintenance Management 2004). The concept is simple: pavement preservation needs arise when the predicted pavement condition is lower than the recommended or mandated level-of-service criteria. The key for the successful operation of this model is the objective assessment of pavement condition and the establishment of the levels of service that are accepted or mandated by deci- sion makers. LEVELS OF SERVICE AND TRIGGER LEVELS Pavement preservation needs depend on the level of service the airport pavements are expected to provide. A higher level of service, for the same pavement structure, results in higher M&R needs and thus in higher agency costs. Levels of ser- vice for airport pavements are typically expressed in terms of PCI values. They are seldom expressed in terms of pavement roughness because of the unavailability of recognized rough- ness criteria for in-service airport pavements (Larkin and Hayhoe 2009). However, the FAA is developing new guide- lines on roughness of in-service airport pavements as dis- cussed in chapter three. Level of Service There are several types of level of service that may be used to establish the amount of maintenance and rehabilitation air- port pavements may require. Target Level of Service The target or the desirable level of service can be expressed only as an average condition of all pavement sections for a given airport facility. The target level of service is specified for different facility types because all facilities do not require the same target level of service. An example is provided in Table 7. For comparison purposes, this table also includes the minimum acceptable level of service, which is discussed subsequently. If the target level of service is approved and mandated by the airport management it can be used to deter- mine the pavement preservation strategy to provide the man- 22 dated level of service. In other words, the pavement preser- vation needs become justified and mandated on the basis of approved criteria. The levels of service given in Table 7 are example levels and are included herein for a medium-sized general aviation airport for illustrative purposes only. It is noted that levels of service in terms of PCI depend on several factors: • Airport type and size—General aviation airports may have lower target levels of service than carrier airports, particularly large carrier airports. • Facility type—Higher target levels of service are typi- cally required for runway pavements than for pave- ments on taxiways or aprons. Also, some airports may use higher target levels of service for primary facilities (e.g., primary runways) than for secondary or tertiary facilities. • Number of aircraft operations and aircraft size—Higher target levels of service are typically required for facili- ties serving a larger number of aircraft operations or larger and heavier aircraft. • Pavement type—Some agencies use different levels of service for different pavement types (Utah Continuous Airport System Plan 2007). Minimum Acceptable Level of Service The minimum acceptable level of service can be expressed as the average condition for all sections for a given facility type or as the minimum acceptable level of service for individual pavement sections (see Table 7). The sections at or below this minimum acceptable level of service are slated for M&R at the first opportunity. The establishment of the minimum acceptable levels of service also provides rational justifica- tion for pavement maintenance and rehabilitation needs. The minimum acceptable levels of service are also called critical levels or critical PCI values. Safety-related Level of Service The safety-related level of service is typically defined in terms of minimum recommended friction levels for runway pavement surfaces given in FAA Advisory Circular on Mea- surement, Construction, and Maintenance of Skid-resistant Airport Pavement Surfaces (2004). The safety-related level CHAPTER FIVE IDENTIFICATION OF NEEDS

23 of service can also be defined in terms of other pavement sur- face defects such as rutting depth. Trigger Levels In addition to using levels of service to estimate the need for pavement M&R, trigger levels provide timing guidance for pavement M&R treatments. An example of levels of service and trigger values is provided in Figure 13. Trigger values may be general or treatment specific. General Trigger Levels General trigger levels provide guidance on what types of M&R treatments are considered for a given pavement condition. For example, MicroPAVER enables the user to specify the PCI levels that trigger a reha- bilitation treatment. Treatment-Specific Trigger Levels These trigger levels are related to the need to apply a preservation treatment at the right time to be effective, before the pavement reaches a con- dition where a different, more expensive treatment would be needed. For example, sealing of cracks in AC pavements is most effective when the pavement is still in very good con- dition. An example of a trigger level for crack sealing and for an overlay is shown in Figure 13. Closely related to the concept of trigger levels is the link- age between specific pavement surface distresses and the rec- ommended pavement M&R treatments. An example of the linkage between pavement cracking and recommended pave- ment M&R treatments is shown in Table 8. The relationship shown in this table, developed for all key pavement dis- tresses, is called a maintenance policy in MicroPAVER. IDENTIFICATION OF NEEDS Identification of needs on the network level consists of the following four steps: 1. Identification of pavement sections that require M&R treatments because of the level-of-service require- ments or because of trigger levels. 2. Selection of M&R treatments for the sections identi- fied in step 1. 3. Estimation of the costs for the implementation of M&R treatments selected in step 2. 4. Prioritization of projects if the cost of the treatments, estimated in step 3, exceeds the available budget. The selection and prioritization of projects is done system- atically and objectively using the procedures described in the next chapter. Identification of needs is discussed separately for two time horizons: • Short-term planning for time horizons of about 5 years or less. For simplicity, it is also assumed that the ana- lytical procedures used for short-term planning do not include the generation and evaluation of alternative treat- ments in future years. • Long-term planning for time horizons of more than 5 years. In this case, analytical procedures can include the generation and evaluation of alternative treatments in future years. Short-Term Planning Many airports use short-term planning to identify and prior- itize pavement M&R needs. The typical procedure consists of the following steps: a) Updating Pavement Inventory—Pavement inventory, including pavement condition, is updated. The update includes results of all recent pavement-related projects and other changes to the pavement infrastructure. 100 0 Pavement age, years Pa ve m en t C on di tio n In de x, P CI Minimum acceptable level of service for individual sections Trigger level for crack sealing Trigger level for overlay (mill and fill) Target level of service for average network condition Performance curve FIGURE 13 Example of levels of service and trigger levels. Level of Service Average PCI for all Sections Facility Type Target or desirable Minimum acceptable Minimum Acceptable Level of Service PCI for Individual Sections Runway 80 65 55 Taxiway 70 60 45 Apron 70 60 40 TABLE 7 EXAMPLE LEVELS OF SERVICE FOR A MEDIUM-SIZE GENERAL AVIATION AIRPORT WITH AC PAVEMENTS

b) Defining Scope of Work—Pavement preservation treatments that can be planned at least a year in advance are included, whether corrective maintenance, preven- tive maintenance, or rehabilitation treatments. The treat- ments may include, for example, sealing of cracks and joints, AC overlays, full-depth repairs of PCC pave- ments, and installation of subdrains. c) Reviewing Pavement Preservation Needs for Each Air- port Pavement Section—One of the reasons for dividing a pavement network into sections is to create future pavement repair units. Each section is considered in turn to decide if the section is expected to require any M&R work during the next 5 years, or during the given plan- ning horizon. Many sections may not require any treat- ment during the planning horizon, whereas other sec- tions may require preventive maintenance or other types of treatments. The decisions are based on the mandated levels of service (Table 7) and trigger values such as those shown in Figure 13. The needs take into account expected pavement deterioration during the planning period. The identification of needs is documentation of the needs that are necessary on the basis of the levels of service. An example of pavement preservation needs for a small airport (shown in Figure 7) is given in Table 9. Table 9 was generated by MicroPAVER. In this exam- ple, the costs of the major M&R treatments depend on the PCI levels. The actual type of M&R treatments is not defined. d) Selecting Treatment Types—To refine the cost esti- mates, airport pavement maintenance managers select 24 the M&R treatment. Figure 14 provides a summary of survey responses regarding the methods used for the selection of M&R treatments. For example, about 85% of respondents use engineering judgment and 30% of the respondents use computer-based tools. Decision trees were used by about 6% of the respondents. How- ever, engineering judgment often includes reasoning that has the structure of decision trees. The need for maintenance treatments, particularly preventive maintenance treatments, is determined using trigger values for individual pavement surface dis- tresses. For example, using the PCI pavement distress evaluation terminology, the occurrence of joint seal damage at the medium or high severity triggers the need for joint sealing, and the occurrence of corner break at the medium or high severity levels triggers the need for full-depth patching with PCC. An example of the network-level maintenance plan generated by MicroPAVER for the small airport shown in Figure 7 is shown in Table 10. The exact extent of maintenance work is determined on the project level. For example, the existence of the 11 corner breaks was estimated by sampling (and not by an actual field count) and verified by a detailed survey on the project level. Similarly, the size of the full-depth patches to repair the cracks needs to be determined individually for each crack repair. For localized M&R treatments, MicroPAVER uses maintenance polices that match the distresses with M&R treatments (Table 8). Major M&R treatments are identified as a function of the PCI level in terms of costs only (Table 9). Other software packages identify generic Plan Year Branch Name Section Number Section Area, ft2 Maintenance, $ Major M&R, $ Cost, $ 2009 A01 10 48,000 0 238,000 238,000 20 46,000 49,400 0 49,400 THEAST 10 17,800 0 97,100 97,000 RW1533 10 205,600 0 945,900 945,900 2010 No work identified 2010 No work identified etc. 5-year plan total 49,400 1,794,700 1,844,100 Source: Michigan Airports Division (2007). TABLE 9 EXAMPLE OF 2009 5-YEAR MAJOR M&R PLAN FOR UNLIMITED BUDGET Recommended Maintenance Treatment Severity of Pavement Cracking AC pavements PCC pavements Low None—continue to monitor None—continue to monitor Medium Crack routing and sealing Crack sealing High Crack repairs Full-depth repairs TABLE 8 EXAMPLE OF MAINTENANCE POLICY FOR CRACKING

25 treatment types; for example, an AC overlay, and the corresponding cost of the generic treatment types. The actual treatment design, including the design of pre- overlay improvements, overlay thickness, and material properties, is done on the project level. e) Selection of Preventive Maintenance Treatments— About 56% of airports systematically identify pave- ments that would benefit from preventive maintenance and 35% of airports do so when budget permits (Figure 14). For comparison purposes, Figure 15 also shows that 33% of airports have dedicated budgets for preventive maintenance. The existence of a dedicated budget for preventive maintenance is considered to be one of the prerequisites for timely, successful, and sustainable oper- ation of preventive pavement maintenance programs. Long-Term Planning Long-term planning for airport pavement maintenance needs can improve engineering and economic decision making by helping answer the following example questions: • What will be the condition of the pavement network 10 years from now given the existing budget? • What is the future funding to achieve a specified level of service? • How much additional funding will be needed in the future to compensate for reduced funding now? • What would be the impact on the network condition of diverting funds to preventive maintenance or lower- cost treatments? • What would be the impact of constructing new runways or taxiways on the pavement preservation budget? The accuracy of future funding requirements for airport pavement maintenance depends on the reliability of long- term prediction of pavement performance and the generation of feasible alternatives. Long-term planning and prioritiza- tion can consider, for each section, several treatment options in each analysis year. This results in a large number of pos- sible combinations of program years and treatments for one section alone. The concept of generating alternative M&R treatments for different years is illustrated for one pavement section in Figure 16. For clarity, only two treatments (microsurfacing and overlay) and two analysis years (now-plus-3 years and now-plus-9 years) are considered. Alternative 1 is microsur- Pavement Surface Distress Branch Name Section No. Type Severity Quantity Unit Maintenance Treatment Cost A01 20 Corner break High 11 Slab Full-depth patching with PCC $9,500 Linear cracking Medium 150 Feet Crack sealing $400 Joint seal damage High 460 Slab Joint sealing $34,000 Shattered slab High 4 Slab Full-depth patching with PCC $4,700 Corner spalling High 12 Slab Partial-depth patching with PCC $800 Total $49,400 TABLE 10 EXAMPLE MAINTENANCE PLAN 0 25 50 75 100 Co mp ute r p rog ra m En gin eer ing jud gm en t Wo rst co nd itio n firs t De cis ion tre es Wh en haz ard ex ists Ag e o f p ave me nt Op era tio na l p rio riti es Oth er co ns ide rat ion s Selection of treatments Pe rc en t o f r es po nd en ts FIGURE 14 Methods used to select M&R treatments on the network level. 0 20 40 60 Yes Budget permitting No Have dedicated preventive maint. budget Identification of preventive maintenance treatments Pe rc en t o f r es po nd en ts FIGURE 15 Systematic identification of preventive maintenance needs.

facing to be constructed 3 years from now. Alternative 2 is an overlay to be constructed in year now plus 9 years, when the existing pavement will reach the minimum acceptable level of service. Sophisticated software generates and evaluates multiple treatment options. For the example shown in Figure 16 it means generating the two alternative treatments (microsur- facing and overlay) at two different years, and estimating their life spans. The life spans of the alternatives and their costs are used subsequently to select the most cost-effective alternative. This type of analysis has been carried out by many highway agencies, but is not routinely done by airport agencies. 26 Minimum acceptable service level Overlay 0 100 Now + 3 Pavement age, years Now + 9 Micro-surfacing 2 1 Pa ve m en t C on di tio n In de x Now FIGURE 16 Pavement performance prediction for multi-year identification of needs.

Next: Chapter Six - Prioritization, Planning, and Budgeting »
Common Airport Pavement Maintenance Practices Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s Airport Cooperative Research Program (ACRP) Synthesis 22: Common Airport Pavement Maintenance Practices explores how airports implement a pavement maintenance management program, including inspecting and tracking pavement condition, scheduling maintenance, identifying necessary funds, and treating distresses in asphalt and concrete pavements.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!