1. 1 A General Approach to Equity in Traffic Flow Management and Its Application to Mitigating Exemption Bias in Ground Delay Programs Michael Ball University of Maryland, College Park, MD Thomas Vossen University of Colorado, Boulder, CO Robert Hoffman, Michael Wambsganss Metron Aviation, Herndon, VA

2. Motivation for Ground Delay Programs: airline schedules “assume” good weather SFO: scheduled arrivals: VMC airport acceptance rate: IMC airport acceptance rate:

3. Ground Delay Programs delayed departures delayed departures delayed arrivals/ no airborne holding

4. Collaborative Decision-Making Traditional Traffic Flow Management: Flow managers alter routes/schedules of individual flights to achieve system wide performance objectives Collaborative Decision-Making (CDM) Airlines and airspace operators (FAA) share information and collaborate in determining resource allocation; airlines have more control over economic tradeoffs CDM in GDP context: CDM-net: communications network that allows real-time information exchange Allocation procedures that increase airline control and encourage airline provision of up-to-date information

5. GDPs under CDM Resource Allocation Process: FAA: initial “fair” slot allocation [Ration-by-schedule] Airlines: flight-slot assignments/reassignments [Cancellations and substitutions] FAA: periodic reallocation to maximize slot utilization [Compression] Note: - reduced capacity is partitioned into sequence of arrival slots - ground delays are derived from delays in arrival time

6. Basic RBS Allocation Principle OAG Schedule: arrival rate = 60/hr Degraded Conditions: arrival rate = 30/hr AAL has 3 slots in 1st 10 min AAL has 3 slots in 1st 20 min

7. Key Properties of RBS Allocation independent of current status of flights  –Not affected by information provided by airlines  no disincentive to provide information Based on simple, well-accepted priority scheme (first-come, first-served  first-scheduled, first- served). Delay allocation has all flights as “close to the average as possible”.

8. GDPs and Flight Exemptions GDPs are applied to an “included set” of flights Two significant classes of flights destined for the airport during the GDP time period are exempted: –Flights in the air –Flights originating at airports greater than a certain distance away from the GDP airport Question: Do exemptions induce a systematic bias in the relative treatment of airlines during a GDP??

9. Analysis of Flight Exemptions (Logan Airport) Flight exemptions introduce systematic biases: USA (11m/flt), UCA (18m/flt) “lose” under exemptions

10. GDPs as Balanced Just-in-Time Scheduling Problem flts nb Xb na time Airlines = products, flights = product quantities Minimize deviation between “ideal” rate and actual production “ideal” production rate Cumulative production Possible deviation measures Vertical deviation horizontal deviation

11. How do we measure deviation from ideal?? slots Number allocated to airline A Ideal allocation to A

12. How do we measure deviation from ideal?? slots Number allocated to airline A Ideal allocation to A Horizontal deviation: When did A get 3 rd slot vs when should A get 3 rd slot?? Vertical deviation: After time t, how many slots did A receive vs how many should have A received?? Actual allocation to A

13. How do we minimize deviation from ideal?? Two models based on horizontal deviation measure: Assignment model: Min  airlines  slots (ideal slot k – actual slot k) 2 “Greedy Algorithm” – looks more like current rbs Also models based on vertical deviation

14. Flight Exemptions Minimize deviations using optimization model that incorporates exemptions reduces systematic biases, e.g. USA from 11m/flt to 2m/flt, UCA from 18m/flt to 5m/flt Deviation RBS ideal-RBS actualDeviation RBS ideal-Opt. model

15. Distribution of delay among flights by airline: Current allocation Allocation by new procedure Delay in minutes num of flights

16. Delay in minutes num of flights Current allocation Allocation by new procedure Distribution of delay among flights by airline (cont):

17. Generality within GDPs Can easily be adapted to manage program dynamics: whenever revisions to programs are required, make changes to approximate “ideal” as best as possible. Can be modified to handle other “constraints” on allocation, e.g. handling “pop-ups”. Provides single approach to both RBS and compression. Could apply other measures/models of deviation from idea, e.g “vertical” models. Could be used with other definitions of an ideal allocation.

18. General Approach to Equity in Air Traffic Management Define ideal allocation Generate optimization model that minimizes deviation between actual allocation and idea.