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22 CHAPTER FIVE IDENTIFICATION OF NEEDS The identification of pavement preservation needs described dated level of service. In other words, the pavement preser- in this chapter is based on the results of pavement condition vation needs become justified and mandated on the basis of surveys, the prediction of pavement deterioration, and the approved criteria. desirable level of service for airfield pavements (Unified Facilities Criteria on Pavement Maintenance Management The levels of service given in Table 7 are example levels 2004). The concept is simple: pavement preservation needs and are included herein for a medium-sized general aviation arise when the predicted pavement condition is lower than airport for illustrative purposes only. It is noted that levels of the recommended or mandated level-of-service criteria. The service in terms of PCI depend on several factors: key for the successful operation of this model is the objective assessment of pavement condition and the establishment of · Airport type and size--General aviation airports may the levels of service that are accepted or mandated by deci- have lower target levels of service than carrier airports, sion makers. particularly large carrier airports. · Facility type--Higher target levels of service are typi- cally required for runway pavements than for pave- LEVELS OF SERVICE AND TRIGGER LEVELS ments on taxiways or aprons. Also, some airports may use higher target levels of service for primary facilities Pavement preservation needs depend on the level of service (e.g., primary runways) than for secondary or tertiary the airport pavements are expected to provide. A higher level facilities. of service, for the same pavement structure, results in higher · Number of aircraft operations and aircraft size--Higher M&R needs and thus in higher agency costs. Levels of ser- target levels of service are typically required for facili- vice for airport pavements are typically expressed in terms of ties serving a larger number of aircraft operations or PCI values. They are seldom expressed in terms of pavement larger and heavier aircraft. roughness because of the unavailability of recognized rough- · Pavement type--Some agencies use different levels of ness criteria for in-service airport pavements (Larkin and service for different pavement types (Utah Continuous Hayhoe 2009). However, the FAA is developing new guide- Airport System Plan 2007). lines on roughness of in-service airport pavements as dis- cussed in chapter three. Minimum Acceptable Level of Service Level of Service The minimum acceptable level of service can be expressed as the average condition for all sections for a given facility type There are several types of level of service that may be used or as the minimum acceptable level of service for individual to establish the amount of maintenance and rehabilitation air- pavement sections (see Table 7). The sections at or below port pavements may require. 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- Target Level of Service tion for pavement maintenance and rehabilitation needs. The minimum acceptable levels of service are also called critical The target or the desirable level of service can be expressed levels or critical PCI values. 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 Safety-related Level of Service the same target level of service. An example is provided in Table 7. For comparison purposes, this table also includes The safety-related level of service is typically defined in the minimum acceptable level of service, which is discussed terms of minimum recommended friction levels for runway subsequently. If the target level of service is approved and pavement surfaces given in FAA Advisory Circular on Mea- mandated by the airport management it can be used to deter- surement, Construction, and Maintenance of Skid-resistant mine the pavement preservation strategy to provide the man- Airport Pavement Surfaces (2004). The safety-related level