Browsing by Author "Churchill, Andrew Michael"

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    Coordinated and robust aviation network resource allocation
    (2010) Churchill, Andrew Michael; Lovell, David J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In the United States, flight operators may schedule flights to most airports at whatever time best achieves their objectives. However, during some time periods, both at airports and in the airspace, these freely-developed schedules may become infeasible because weather or other factors reduce capacity. A plan must then be implemented to mitigate this congestion safely, efficiently, and equitably. Current planning processes treat each congested resource independently, applying various rules to increase interoperation times sufficiently to match the reduced capacity. However, several resources are occasionally congested simultaneously, and ignoring possible dependencies may yield infeasible allocations for flights using multiple resources. In this dissertation, this problem of developing coordinated flight-slot allocations for multiple congested resources is considered from several perspectives. First, a linear optimization model is developed. It is demonstrated that optimally minimizing flight arrival delays induces an increasing bias against flights using multiple resources. However, the resulting allocations reduce overall arrival delay, as compared to the infeasible independent allocations, and to current operational practice. The analytic properties of the model are used to develop a rule-based heuristic for allocating capacity that achieves comparable aggregate results. Alternatively, minimizing delay assigned at all resources is considered, and this objective is shown to mimic the flights' original schedule order. Recognizing that minimizing arrival delays is attractive because of its tangible impact on system performance, variations to the original optimization model are proposed that constrain the worst-case performance of any individual user. Several different constraints and cost-based approaches are considered, all of which are successful to varying degrees in limiting inequities. Finally, the model is reformulated to consider uncertainty in capacity. This adds considerable complexity to the formulation, and introduces practical difficulties in identifying joint probability distributions for the capacity outcomes at each resource. However, this new model is successful in developing more robust flight-slot allocations that enable quick responses to capacity variations. Each of the optimization models and heuristics presented here are tested on a realistic case study. The problem studied and the approaches employed represent an important middle ground in air traffic flow management research between single resource models and comprehensive ones.
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    Determining the Number of Slots to Submit to a Market Mechanism at a Single Airport
    (2007-05-09) Churchill, Andrew Michael; Lovell, David J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In this thesis, several stochastic optimization models are presented to determine the number of airport arrival slots that should be made available for distribution via a market mechanism. Considerable attention is paid to the structure and mathematical properties of each of these models, with regards to obtaining integer-valued solutions. Calibration of the various parameters is undertaken using historical data. In addition, an analysis of the average pecuniary valuations assigned to each slot is presented, as this is an essential input to these models. Several methods are suggested by which each of these values can be estimated. The models are intended to be taken in a general context, but extensive computational examples making use of data for LaGuardia Airport are provided as a case study in the application of the various techniques presented herein.