Air Traffic Control Facilities: Improving Methods to Determine Staffing Requirements Improving Methods to Determine Staffing Requirements -- Special Report 250 (1997) / Chapter Skim
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TRANSPORTATION RESEARCH BOARD 1997 ExEcunvE COMITTEE CHAIRSIAN: DAVID N WORMLEY, Dean of Engineering, Pennsylvania State University, University Park VICE CHALItsIAN: SHARON D
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S PEC it RPOR1 250 AN Ifif f IC CON1901 f ACI 11110 IMPROVING AETHODS TO DITIRAINI STAMING REQuIREAENTS Comm iftee To Study the federal Aviation Administralion's Methodologies for [stimating A i r T r a f f i c Controller Staffing Standards Transporafion Research Board Nafional Research Council Nafional icodemy Press Washington, D
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Transportation Research Board Special Report 250 Subscriber Category V aviation Transportation Research Board publications are available by ordering individual publications directly from the TRB Business Office, through the Internet at http://www.nas.edultrb/index.html, or by annual subscription through organization or individual affiliation with TRB. Affiliates and library subscribers are eligible for substantial discounts.
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Committee To Study the Federal Aviation Administration's Methodologies for Estimating Air Traffic Controller Staffing Standards AARON COHEN, Chairman, Texas A&M University, College Station CHARLES B AALFS, Federal Aviation Administration (retired)
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PREfACE The appropriate level of staffing for air traffic control has long been controversial. Following the controller strike in 1981, which resulted in the firing of two-thirds of the controllers, congressional concerns about staffing, were focused primarily on the overall size of the work force.
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vi PREFACE was also recognized that, although Congress posed a highly technical question, any study of methods to determine appropriate staffing levels would raise hotly debated questions about work rules, productivity, compensation, management practices, and other issues. Although these issues do affect total staffing levels, they extend well beyond the technical boundaries of this study and are not examined in detail as part of this report.
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PREFACE vii Chief Petty Officer Kathleen Shanahan of the U.S. Navy, who described how staffing requirements are estimated for air traffic control at military facilities; Jack Knight, who described how staffing requirements are determined for flight controllers at the National Aeronautics and Space Administration's Johnson Space Center; and Kathy Fox, who provided information about the determination of staffing and scheduling requirements for air traffic controllers in Canada.
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CON If N IS FINDINGS AND RECOMMENDATIONS . 1 INTRODUCTION .................................10 Request for Study and Scope of Work 10 The Airport and En Route Air Traffic Control System 11 Staffing Air Traffic Control Facilities 15 Outline of Report 20 2 CURRENT STAFFING PROCESS: DESCRIPTION AND SHORTCOMINGS ...................
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fINDINs AND R[COMM[NDAIIONS The Federal Aviation Administration (FAA) has developed quantitative models known as staffing standards to estimate the number of air traffic control specialists (ATCSs)
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AIR TRAFFIC CONTROL FACILITIES It is not possible to test the validity of the FAA headquarters staffing standards at the facility level in an empirical, scientific way, because FAA does not have formal performance criteria or systematically collected measures of air traffic control system performance related to staffing against which to compare model-predicted estimates. For a model to have validity in the scientific sense, predictions of the model must be tested, directly or indirectly, against some external measure (i.e., criterion)
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FINDINGS AND RECOMMENDATIONS system performance. A high, statistically significant correlation would imply that the staffing standards are valid.
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AIR TRAFFIC CONTROL FACILITIES 2. Can the current staffing standards be modified to provide more accurate estimates?
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FINDINGS AND RECOMMENDATIONS 3. What alternative approaches could be pursued?
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6 AIR TRAFFIC CONTROL FACILITIES in the regions by a less formal "bottom-up" approach (see accompanying diagram)
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FINDINGS AND RECOMMENDA TIONS Collection of more data and trial use of state-of-the-art clustering techniques to group facilities, or sectors3 within or among facilities, with like characteristics to support development of separate models for these groups if statistically significant differences are found. Inclusion of more of the factors that affect controller performance directly in the models.
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8 AIR TRAFFIC CONTROL FACILITIES and reporting format for providing regionally based estimates of facility staffing, which are one element of the overall staffing process. The most desirable approach for strengthening the regional component of the staffing process would be for headquarters to gather and share information with the regions on best practices in individual regions and, once consensus on an approach is reached, to establish it uniformly across the regions.
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FINDINGS AND RECOMMENDATIONS 9 cations of different levels of facility staffing, which, over time, could provide the basis for validating facility staffing estimates. NEXT STEPS The committee strongly urges that FAA headquarters ensure that action is taken on the elements of the improved staffing process recommended in the preceding section.
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INTRODUCTION All models are wrong but some are useful.
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INTRODUCTION 11 ber of controllers at each of its facilities" (Appendix A)
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En Route 7 Tower M Center controllers clear the lane to land -- Navigation Transmitter - on ! gatIo ' Transmitter SurfaceN9ation En Rou 4 Center Inside the en route - center, flights are handed detection from controller to kirpo r controller, each Te1 overseeing a particular slice of airspace 6 As the plane nears its destination, control _ 3 The fit ht is then transmitters goes to a radar-approach controller _________ Terminal radar- taken ovjby an route send signals approach control centers across the to help pilots the who guides the plane to the runway (TRACON)
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14 AIR TRAFFIC CONTROL FACILITIES weather is present, the control task is even more demanding. Center controllers may be required to delay the passage of aircraft out of their sectors to meter traffic flow into terminal areas (OTA 1982, 37)
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INTRODUCTION 15 Sectors For air traffic control purposes, the airspace system has been divided into many small, contiguous sectors. Each sector is defined in terms of its horizontal and vertical extent and is the responsibility of an air traffic controller at a particular facility (OTA 1982,36)
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16 AIR TRAFFIC CONTROL FACILITIES FAA's staffing standards apply to controllers whose primary responsibility is the separation and control of aircraft or the provision of flight information services -- the air traffic control specialists (ATCSs) ;4 they do not apply to supervisory personnel.
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18 AIR TRAFFIC CONTROL FACILITIES available, traffic flow is restricted or aircraft are held outside of the affected area to ease the work load. Thus system efficiency is reduced to avert any adverse effects on safety.
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INTRODUCTION 19 different facility or sector conditions.'1 Without a better understanding of the factors that affect controller performance, the current staffing standards can only provide a gross measure of the differences in staffing requirements within and across facilities. Expected Changes in the Work Environment Expected changes in the air traffic control environment are likely to affect the nature of controllers' tasks and possibly the level of staffing.
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20 AIR TRAFFIC CONTROL FACILITIES Automated air traffic control systems may change the role of the controller and therefore the requirements for staffing. However, until these systems are operationally tested and procedures of use are established, changes in staffing requirements would be 'difficult for FAA to forecast.
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INTRODUCTION 21 Mogford, R.H., J.A. Guttman, S.L.
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PA CURRENT STAfflN6 PROCESS: DESCRIPTION AND SHORTC0MIN6S A cen' tral mission of the Federal Aviation Administration (FAA) is to manage airspace and control air traffic operating in that airspace.
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I STEP1 I FAA Headquarters Develops National and Regional Staffing Estimates Based on Staffing Standards Each Region in Proportion to Staffing Standard Estimates, Adjusted for Actual Funding Available + Can Request Changes to FAA Headquarters Funding Allocation + Negotiates Final Funding Allocation with FAA Headquarters Develops Estimates of Facility-Level Staffing Requirements Within FAA Headquarters Funding Allocation + Negotiates Staffing Levels and Allocates Staffing Among Individual Facilities FAA Facility FIGURE 2-1 Overview of FAA staffing process.
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24 AIR TRAFFIC CONTROL FACILITIES FAA Headquarters Staffing Process The staffing standards are the centerpiece of the FAA headquarters process of estimating ATCS staffing requirements. What Is a Staffing Standard?
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CURRENT STAFFING PROCESS 25 standard) , to more scientifically based standards using modified industrial engineering techniques to measure controller work load (first introduced in 1973)
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FAA HEADQUARTERS STAFFING STANDARDS -- How THEY WORK IN BRIEF In general, staffing estimates are built on empirical measurements of controller work as a function of aircraft activity (S. Helzer, air traffic briefing to committee, May 30, 1996)
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CURRENT STAFFING PROCESS 27 A basis for informing management of how resources are used; and A baseline for "what if" analyses of future scenarios, including proposed program changes, expansion, or reduction; consequences of not staffing at full levels; and impacts of using overtime. In practice, FAA headquarters staffing standards are used primarily as a budgeting and resource allocation tool.
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FAA Headquarters (HO) Develops Regional ATCS Staffing Requirements Applying the Staffing Standards FAA HO Adds Other Staffing Requirements to Develop Regional Totals + FAA HO Identifies National Funding Available for Air Traffic FAA HO Compares Budgeted Funds with Staffing Standard Estimates + F OAdjustsnal Totals ortionately FAA HO Provides Regions with Adjusted Lump Sum Staffing Allocations FAA HO Responds to Regional Requests for Changes to Staffing Allocations FIGURE 2-2 FAA headquarters staffing process.
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CURRENT STAFFING PROCESS 29 requirements and special needs, which may result in facility staffing levels that differ from headquarters model-derived numbers (FAA 1996a, 5)
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30 AIR TRAFFIC CONTROL FACILITIES SOUTHWEST REGION STAFFING APPROACH The staffing needs of this region are reviewed at least annually. The air traffic manager of each facility is responsible for identifying die staffing needs of the facility and reporting them to the regional office.
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CURRENT STAFFING PROCESS 31 Regions Solicit Facility Staffing Needs Needs Analysis and Justify Regions Receive Facility Staffing Regions Review Estimates and Facility Staffing Overall Regional __ Plans and Staffing Allocation Forecasts from Headquarters Regions Develop Staffing Proposal and Solicit Facility Review + Facilities Review Regional Staffing Allocation and Comment Back to Regions + Regions Finalize Facility Allocations and Forward Them to Facilities FIGURE 2-3 FAA regional staffing process. dards were not developed for this purpose, but could they be modified to meet this objective?
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32 AIR TRAFFIC CONTROL FACILITIES two general categories -- the characteristics of the staffing standards themselves and the staffing process of which the models are only one part. A more detailed discussion of these issues can be found in Appendix C
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CURRENT STAFFING PROCESS 33 opment of the staffing standard for TRACONs to examine the potential for developing separate work-time models for different subsets of the data (e.g., organized by sector size and tpe)
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34 AIR TRAFFIC CONTROL FACILITIES results are adjusted by a factor that nearly doubles the staffing numbers. The currently used 1.76 adjustment factor takes into account 7-day facility operation.
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CURRENT STAFFING PROCESS 35 The more critical problem occurs in forecasting future year air traffic. To predict the staffing required to meet future year traffic levels, baseline data on facility traffic for the 90th percentile or 37th-busiest day of the preceding year are gathered.
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36 AIR TRAFFIC CONTROL FACILITIES tors account for most of the differences. First, more controllers are sometimes required for a sector than the national staffing standard assumes.
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CURRENT STAFFING PROCESS 37 Use of Headquarters Staffing Standards As indicated at the outset of this chapter, the staffing standards are only one input to the process of estimating staffing requirements and making facilitylevel staffing decisions. Discrepancies between facility staffing estimates produced by FAA headquarters and those determined by the regions reflect the different processes used by the FAA regions to determine facility staffing requirements.
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38 AIR TRAFFIC CONTROL FACILITIES Lack of Validation Measures Until an external criterion is developed against which estimates of staffing requirements can be compared, there is no objective basis on which Congress, FAA headquarters, or the FAA regions can determine whether a spccific facility has the optimum number of ATCSs, whatever staffing standard or staffing approach is used. The current FAA headquarters staffing standards have not been validated in this sense, and such validation is not easy.
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CURRENT STAFFING PROCESS 39 could provide the basis for developing a better approach to estimating staffing requirements for individual facilities, the subject of the next chapter. REFERENCES ABBREVIATIONS ERAT Eastern Region Assessment Team FAA Federal Aviation Administration GAO General Accounting Office STI Standards Technology, Inc.
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3 STRAT[6Y FOR AN IMPROV[D SIAFFIN6 PR0C[ss The congressional request for more accurate estimates of controller staffing at individual facilities is best addressed by focusing on the two-part process by which staffing requirements are determined rather than on the Federal Aviation Administration (FAA) headquarters staffing standards alone.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 41 form process -- agreed upon by FAA headquarters, regional, and facility staff -- for estimating, reviewing, and reconciling facility staffing estimates. The process should build on the strengths of the current staffing system.
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42 AIR TRAFFIC CONTROL FACILITIES IMPROVING THE HEADQUARTERS STAFFING PROCESS After considering several alternatives, the committee concluded that an improved headquarters staffing process should start, as it does now, with initial headquarters and regional estimates of staffing requirements for all air traffic control facilities. This conclusion was based on the analysis that follows, which supports the role of and continuing need for headquarters staffing standards.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 43 $500,000 because of the substantial data collection required. However, user acceptance of the approach, specifically its subjectivity, was perceived to be a major drawback.
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44 AIR TRAFFIC CONTROL FACILITIES within or among facilities, with similar characteristics as the basis for supporting development of separate models for these groups if statistically significant differences among clusters are found. The many factors that affect controller work time could be screened to identify those highly correlated with differences in work performance.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 45 and second, if increased automation and procedural changes in the air traffic control system result in major changes in the nature of controllers' work that would likely render the current models obsolete. One method that warrants consideration is a task analysis -- based modeling approach.
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46 AIR TRAFFIC CONTROL FACILITIES TASK ANALYSIS -- BASED MODELING APPROACH Development of the model would require the following steps: Detailed descriptions of controller operations at representative sites and development of a systematic classification of controller tasks, subtasks, and work elements by sector (i.e., position) based on the descriptive information would be required.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 47 should present model-developed staffing estimates with statistical confidence intervals9 to define for users, such as the oversight team or congressional staff, the statistical accuracy of the estimates. IMPROVING THE REGIONAL STAFFING PROCESS Whatever changes are adopted at the headquarters level, the regional approach to developing estimates of facility staffing requirements should be retained and strengthened by the adoption of a uniform approach to determining facility staffing requirements across the regions.
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48 AIR TRAFFIC CONTROL FACILITIES staffing requirements. In an improved staffing system, a headquarters-level oversight process should be established to review, explain, and reconcile differences between headquarters and regional estimates.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 49 worth exploring for their links with staffing levels. It would also include performance measures.
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50 AIR TRAFFIC CONTROL FACILITIES shelf" approaches or methods that FAA could adopt to improve staffing estimates.12 Two approaches were found that merit further consideration. First, the United States armed forces have developed a bottom-up staffing approach for military controllers.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 51 UNITED STATES AIR FORCE STAFFING PROCESS FOR AIR TRAFFIC CONTROL: A BOTTOM-UP APPROACH The United States armed services use a standardized, bottom-up, position-based staffing approach and oversight process for estimating staffing requirements for air traffic control. The Air Force staffing process provides a good illustration of how the approach works.
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52 AIR TRAFFIC CONTROL FACILITIES AUTOMATED STAFFING PROCESS FOR AIRPORT OPERATIONS Determining staffing requirements and assigning the personnel needed to support airport operations is often a labor-intensive, manual process that calls for detailed analysis of flight schedules, employee availability, scheduling constraints, and service and cost considerations. Commercial organizations have developed computerized decision support systems to help the airlines determine the level of staffing required to support scheduled flights.
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STRATEGY FOR AN IMPROVED STAFFING PROCESS 53 proach, FAA headquarters should establish it uniformly across the regions and provide training, if needed, in its use. Third, a headquarters-level oversight process should be established to review and reconcile differences between headquarters and regional estimates of facility-level staffing requirements.
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APPENDIX A CoNRfssIoNAL REQuEST fOR STAffING STANDARDS STUDY U S Congress, House Committee on Appropriations, H
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APPENDIX B CALCULATION Of fACILITY STAffIN6 REQUIREMENTS A key function of staffing standards is to provide an objective method for determining staffing requirements. In this appendix, a description is provided of the steps involved in the Federal Aviation Administration's (FAA's)
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Identification of Measurement Methodology and Data Measures I Data Collection Development of ATCS Work- Time Models Application of Work-Time Models to Facility 24-hour Traffic Requirements for Each Time Frame in 24hour Day Detailed Facilit Traffic Activity Traffic Count Computer Program Number I Shifts, Shift I Lengths, Shift I Start Times, I I Break I Requirements Application of Development of Scheduling Scheduling 1 Algorithm Model Staffing Application of Forecasting Models 90% ~Da Facility Fore Facility Staffing Adjustment for Off-Position Activities and 7- day Covera e Annual Facility Staffing Requirement
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58 AIR TRAFFIC CONTROL FACILITIES quirements to reflect scheduling constraints by applying a scheduling algorithm (Boxes 6 and 7 of Figure B-i)
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TABLE B-2 SUMMARY OF METHODOLOGIES AND MODELING ASSUMPTIONS USED IN THE DEVELOPMENT OF FAA STAFFING STANDARDS FOR MAJOR TYPES OF FACILITIES FACILITY TYPE NUMBER OF SAMPLE FACILITIES TASK ANALYSIS METHODOLOGY AND SAMPLING POSITIONS INTERVAL COVERED WORK-TIME MODEL ANALYSIS METHOD MODEL ADJUSTMENTS To DETERMINE STAFFING REQUIREMENTS FORECASTING MODEL ANALYSIS METHOD Air route 1985 study: six Timestudy; Radar, handoff, Linear regression Constant for Linear regression traffic ARTCCs 15-n-Lin coordinator, Dependent variable: "look at Dependent variable: control 1991 revalidation intervals and flight data total work in minutes display" time 24-hr controller centers study: three Independent "Difficulty" staffing requirement (ARTCCs) ARTCCs not variables:" number of factor, 90 Independent variable: visited in sector aircraft percent number of facility 1985 study minutes during a 15- confidence operations in 24-hr min interval; number level except period of aircraft leaving a for 1- Note: forecasting sector during a 15- controller model is developed for min interval; number model, which each ARTCC • of aircraft remaining used 95 in a sector during percent the entire 15-min confidence interval; maximum level instantaneous number 1.76 adjustment • of aircraft in a factor for 7- sector during a 15- day coverage min interval and off- position activities (continued on next page)
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TABLE B-2 (CONTINUED) MODEL TASK ANALYSIS ADJUSTMENTS To METHODOLOGY DETERMINE NUMBER OF AND SAMPLING POSITIONS WORK-TIME MODEL STAFFING FORECASTING MODEL FACILITY TYPE SAMPLE FACILITIES INTERVAL COVERED ANALYSIS METHOD REQUIREMENTS ANALYSIS METHOD 2.5 controllers for each manual/oceanic sector for a 24-hr day Terminal 1991 study: 35 Time study; Radar, handoff Linear regression Constant for Linear regression radar TRACONs, 15-min coordinator, Dependent variable: "look at Dependent variable: approach partially random intervals and flight data total work in minutes scope" time annual controller control sample Independent variables: "Difficulty" staffing requirement facilities stratified by total number of factor, 90 Independent variables: (TRACONs)
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a facility during a 90th percentile for two types of 15-min interval busiest day TRACONs -- ARTS II (flight data model traffic and ARTS III only) forecast facilities Air traffic 64 ATCTs for work Time study Local control, Simulation model based Constants for Linear regression control sampling and work ground control, on time study to other work not Dependent variable: towers 26 ATCTs for time sampling; and clearance estimate work time in accounted for annual controller (ATCTs)
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TABLE 6-2 (CONTINUED) TASK ANALYSIS METHODOLOGY NUMBER OF AND SAMPLING FACILITY TYPE SAMPLE FACILITIES INTERVAL POSITIONS COVERED WORK-TIME MODEL ANALYSIS METHOD MODEL - ADJUSTMENTS To DETERMINE STAFFING REQUIREMENTS FORECASTING MODEL ANALYSIS METHOD 90th percentile busiest day traffic forecast Automated 1994 study: nine Time study; In-flight, EFAS, Work-time equations are Constants for Linear regression flight AFSSs, non- 1-hr preflight, developed to calculate such work Dependent variable: service random selection intervals data, total work in minutes elements as number of controllers stations process broadcast, and by position for a 1-hr "review required for the 90th (AFSSs)
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where the dependent and weather variable is typically observation total work in minutes positions and the independent Leveling variable is some analysis to measure of activity equalize For tasks without performance of readily identifiable noncritical drivers, a constant tasks among time is used, defined time study as the average intervals percentage of time 1.76 adjustment expended on these factor for 7-day tasks converted into coverage and off- minutes from the 1-hr position activities time study samples . 90th percentile busiest day traffic forecast NOTE: ARTS = automated radar terminal system; IFR = Instrument Flight Rules; \'FR = Visual Flight Rules; EFAS = Enroute Flight Advisory Service.
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64 AIR TRAFFIC CONTROL FACILITIES Application of these methodologies requires defining small, discrete divisions of work, called work elements. The appropriate unit of analysis was deemed to be a sector in an air traffic control facility.
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CALCULATION OF FACILITY STAFFING REQUIREMENTS 65 gies must be determined for site selection and work measurement. As noted in Chapter 2, FAA contractors designed their sampling strategies for development of national-level staffing standards.
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66 AIR TRAFFIC CONTROL FACILITIES work time and work load for most of the key work elements. Thus, linear regression was deemed to be an appropriate model form.
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TABLE B-3 SINGLE-CONTROLLER WORK-TIME MODEL FOR TRACONs (STI 1991a, B-7) ELEMENT INTERCEPT COMILTOT GATOT Look at scope/keyboard and trackball 0.5612 0.0144 0.0232 Combined for process flight strip 0.4925 - 0.0316 Combined for communicate with aircraft - 0.5096 0.5480 Combined for related activity 0.0976 - - Combined for interphone communication 0.4460 - 0.0313 Combined for within facility communication 0.1291 0.0066 0.0160 Total 1.7264 0.5296 0.6501 Look at scope 1.0000 Variability .
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68 AIR TRAFFIC CONTROL FACILITIES TAB[E B-5 FLIGHT DATA CONTROLLER WORK-TIME MODEL FOR TRACONs (STI 1991a, 13-10) ELEMENT INTERCEPT FACAC Combined for keyboard activity 0.6313 - Combined for walk 0.6105 0.0257 Combined for distribute strips 0.6494 0.0542 Combined for process strips 5.4306 0.0827 Voice communication 0.8873 - Related activity 0.9099 - Total 9.1190 0.1626 NOTE: TWFD = 9.1190 + (0.1626*
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CALCULATION OF FACILITY STAFFING REQUIREMENTS 69 cedure similar to that for the other staffing standards was used to pool the work and work load data from the sample sites to develop the time allowances for work not accounted for by the simulation model. Step 4: Application of Work-Time Models Because air traffic control work load fluctuates, a major purpose of the worktime models is to ensure adequate staffing for work load peaks.
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70 AIR TRAFFIC CONTROL FACILITIES Adjustments for Scheduling Step 1: Development of Scheduling Model Air traffic control facilities require several shifts to cover peaks in work load and around-the-clock operation. Thus, shift scheduling is important to ensure adequate daily staffing to meet peaks in activity and to allow for meals and breaks.
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CALCULATION OF FACILITY STAFFING REQUIREMENTS 71 staffing requirements. Using data on daily schedule-adjusted staffing requirements as the dependent variable and on daily facility traffic counts and other measures of traffic activity as the independent variables, a regression line is fitted.
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72 AIR TRAFFIC CONTROL FACILITIES position activities represent facilitywide averages. The current adjustment factor, calculated by dividing the total hours per year (2,087)
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APPENDIX C RvIw of SHORTCOMINGS IN CURRENT STAffING STANDARDS fOR APPLICATION TO INDIVIDUAL fACILITIES A more detailed review of Federal Aviation Administration (FAA) headquarters staffing standards from the perspective of their application to individual facilities is provided in this appendix.
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74 AIR TRAFFIC CONTROL FACILITIES staffing models are to play a role in a strengthened headquarters-regional staffing process. Better documentation should increase understanding and use of the models and should assist verification and reviews of methodological approaches.
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SHORTCOMINGS IN CURRENT STANDARDS 75 FAA selected time study and work sampling as its primary methods of collecting work data.6 These are well-known industrial engineering methodologies for studying worker performance. The agency's choice was a good one.
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76 AIR TRAFFIC CONTROL FACILITIES separation of aircraft -- into small, discrete divisions of work, called work elements (STI 1991b, 10)
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SHORTCOMINGS IN CURRENT STANDARDS 77 collected for the four-controller position (Cullinane 1996, 18) .8 The effect of undersampling of these positions on the validity of the data cannot be determined.
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78 AIR TRAFFIC CONTROL FACILITIES The net effects of these changes on the consistency of the data cannot be assessed. Work Load Sampling Aircraft activity is the key factor that determines ATCS work load and the time required to perform work.
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SHORTCOMINGS IN CURRENT STANDARDS 79 To ensure consistency and uniformity in data collection among the 05-3 observers, a comparison of observers' data was made. Two 05-3 observers monitored one radar position simultaneously.
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80 AIR TRAFFIC CONTROL FACILITIES gathering work samples (100 samples) at one site at $16,600.
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SHORTCOMINGS IN CURRENT STANDARDS 81 Representativeness of the Models One of the primary reasons why FAA's staffing standards may not be highly accurate predictors of staffing requirements for individual facilities lies in the treatment of the data inputs to the models. The key data in the work-time models -- controller work times and aircraft activity measures -- are treated as one statistical population.
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82 AIR TRAFFIC CONTROL FACILITIES Predictive Capability of the Models Modeling and quantifying the factors that affect controller work are challenges that the current staffing standards have not fully addressed. During the data collection phase, much information was collected on the complexity of air traffic operations, as well as on the volume and density of air traffic, as factors affecting controller work (STI 1991a, 25; STI 1991b, 8-9)
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SHORTCOMINGS IN CURRENT STANDARDS 83 Sensitivity Estimates Both the work-time and the forecasting models contain numerous adjustment factors and assumptions that are potential sources of error. Among the more important are the choice of the 90th percentile busiest day and the 1.76 adjustment factor in the forecasting models.
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84 AIR TRAFFIC CONTROL FACILITIES dards do not distinguish between weekdays and weekends in applying the work-time models and hence may overstate staffing requirements at certain facilities. Areas for Improvement Perhaps the most promising area for improving the staffing standards for application to individual facilities is to explore the development of work-time models that more adequately represent the different facility types, or the different types of sectors within or among facilities.
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SHORTCOMINGS IN CURRENT STANDARDS 85 they are being used. If the models are used to provide regional estimates for budgeting purposes, their validity should be tested at the regional level of aggregation.
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86 AIR TRAFFIC CONTROL FACILITIES not exclusively driven by the staffing standards. Actual staffing depends on a variety of other considerations.
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SHORTCOMINGS IN CURRENT STANDARDS 87 idation procedures, particularly lack of an external standard against which to compare modeled estimates, make it impossible to test the correctness of the estimates provided by the staffing standards. Finally, use of alternative methods by the FAA regions for estimating staffing requirements for facilities in their regions and factors external to any staffing model are likely to result in continuing discrepancies between FAA headquarters-generated and regional estimates of staffing requirements for some facilities.
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STUDY COAAITTIE BIOGRAPHICAL INfORMATION AARON COHEN, Chairman, is Zachry Professor of Engineering in the College of Engineering at Texas A&M University.
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90 AIR TRAFFIC CONTROL FACILITIES RUSSELL A BENEL is Principal Scientist in System Engineering and Analysis at the Center for Advanced Aviation Systems Development at the MITRE Corporation.
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STUDY COMMITTEE BIOGRAPHICAL INFORMATION 91 JOE D HINsON is Vice President of Global Operations Planning at Federal Express.
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92 AIR TRAFFIC CONTROL FACILITIES ers and TRACONs and as instructor at FAA's Academy in Oklahoma City. At the time of his retirement, he was the Manager of Air Traffic Career Systems at FAA Headquarters.
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STUDY COMMITTEE BIOGRAPHICAL INFORMATION 93 the Human Factors and Ergonomics Society, and the Institute of Electrical and Electronics Engineers Society for Systems, Man and Cybernetics.
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The Transportation Research Board is a unit of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board's purpose is to stimulate research concerning the nature and performance of transportation systems, to disseminate the information produced by the research, and to encourage the application of appro.priate research findings.
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