On Capacity Estimation and Capacity-Safety Relationship in an Air Transportation Network

Abstract

Air transportation is a complex system of interlinked distributed networks in which different components have their own constraints and performance measures. For example, an airport network in which each airport is treated as a node and models the departures/arrivals of flights as links considers capacity as its limiting factor. Whereas, an airspace network that consists of airways (as links) and waypoints (as nodes) providing an orderly flow of air traffic and safe separation between flights considers collision risk as its limiting factor. To accommodate the increasing demand to safely manage air traffic flow, it is imperative to understand the interactions between these two components and the limiting factors that define their characteristics. Understanding this relationship is a major consideration when determining whether and which components should aim to increase safety and capacity. In this thesis, I propose a model for airport network capacity estimation and a model of airspace network risk analysis. I then develop a framework for modelling and integrating airport and airspace networks in an overall air transportation system. Finally, I propose a methodology for determining their complex interactions to analyse the relationship between capacity and safety.

One challenge in analysing the capacity-safety relationship for air transportation is measuring its capacity. In air transportation, capacities have traditionally been measured based on the individual elements of the network, such as links (sector capacity and airspace complexity) and nodes (terminals and runway throughput). These measures obviously do not constitute the overall system-level capacity of a network. This research involves developing a network-level capacity estimation model and method. The proposed model does not require knowledge of an individual airport's capacity and offers an understanding of the relationship between the flow capacity and safety metric of its corresponding airspace.

Experimental and empirical results establish the nature of the relationship between airport network capacity and airspace safety when considered in an interacting air transport system. As the hourly flow increases in the airport network, the overall collision risk increases linearly and, after a certain level, crosses the target level of safety. Such a capacity-safety relationship indicates that the capability of existing air traffic control systems to safely handle projected growth in aircraft operations appears to be artificially limited by the airspace.