During the 1990s, FAA’s staffing models were used mainly to develop national workforce targets for general budgetary decisions. Regional offices generated their own estimates of the number of controllers required per facility. FAA recognized that its national staffing models were too generalized and imprecise to predict staffing needs at each facility. Its models were built on highly aggregated data derived from a small number of sampled sectors and control centers. While considered adequate for generating systemwide estimates of workforce needs, the models lacked the detail needed to inform facility-level planning.

Acknowledging that FAA’s staffing models were not designed to inform facility-level staffing plans, the 1997 TRB study committee nevertheless questioned the models’ use of simple counts of the number of flights traversing a block of airspace as the main indicator of traffic demand on controlling capacity. FAA found that these volume-based measures generated staffing values that were much higher than facility managers believed were reasonable on the basis of demonstrated experience. In particular, the measures did not take into account how the complexity of traffic activity, in addition to its quantity, affects controlling capacity. The committee observed, for instance, that the models employed data on various controller actions that could be readily observed and timed, such as scanning a radar screen, typing on a keyboard, and radioing a pilot. These identified controller actions, however, were not linked to the specific tasks performed by controllers working different types of aircraft activity; for instance, a flight entering the air-space requires the controller to accept the hand-off from another controller, whereas a flight that is changing heading or altitude requires the controller to perform various checks and clearances. Establishing these connections between traffic activity and the actions that controllers must take in response was viewed as critical to developing more accurate estimates of the time demands on controllers.

In particular, the TRB committee recommended that FAA try to quantify the time controllers spend performing specific tasks as they monitor, inform, and direct the actions of aircraft. By modeling traffic activity and coupling this activity with time-varying controller tasks that must be performed in response, FAA could then estimate the total time spent executing tasks, referred to here as “task load.” The TRB commit-



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