ENTITY-CENTRIC ABSTRACTION AND MODELING FRAMEWORK FOR TRANSPORTATION ARCHITECTURES

Journal of Air Transportation, 2006 by Lewe, Jung-Ho, DeLaurentis, Daniel A, Mavris, Dimitri N, Schrage, Daniel P

ABSTRACT

A comprehensive framework for representing transportation architectures is presented. After discussing a series of preceding perspectives and formulations, the intellectual underpinning of the novel framework using an entity-centric abstraction of transportation is described. The entities include endogenous and exogenous factors and functional expressions are offered that relate these and their evolution. The end result is a Transportation Architecture Field which permits analysis of future concepts under the holistic perspective. A simulation model which stems from the framework is presented and exercised producing results which quantify improvements in air transportation due to advanced aircraft technologies. Finally, a modeling hypothesis and its accompanying criteria are proposed to test further use of the framework for evaluating new transportation solutions.

INTRODUCTION

The U.S. transportation system witnessed unprecedented growth in the 20th century. In particular, since the 1960s, the modern aircraft-just like its predecessors, trains and automobiles in their times-has dramatically boosted mobility of the general public. As indicated in Figure 1, the air transportation system picked up momentum after Lindberg's transatlantic flight and yearly domestic enplanements have continued to outnumber the population since 1976, and the spread is expanding.

With further enhancement in mobility, the public could spend less time on travel over a given distance, take longer trips in a given time, and/or travel in ways otherwise not currently possible or affordable. Such a positive scenario, however, is in jeopardy as the rate of expansion of mobility under the current transportation system is reaching a limit on the ground and especially in the air due to (partly unforeseen) growth in congestion, pollution and network delay (AIA, 2001). The aerospace community is undertaking various remedies in the face of this challenge including design of new commercial jets (e.g., Airbus A380 and Boeing 787), enhancement of capacity in both the airspace and terminal area, and development of environment-friendly technologies. Further, targeted research extends to general aviation, where some are experimenting with new types of aircraft and advanced operational structures (e.g., very light jets, on-demand regional air services, and even personal use air vehicles; Holmes, Durham, & Tarry, 2004). The premise motivating most of these initiatives is apparent: advanced technology spurs mobility enhancement. The temptation to look for innovation through technology alone, however, must be resisted. Systems thinking is required, as recognized in NASA's Aeronautics Blueprint: "The aviation system is a system-of-systems. . . . Furthermore, consideration must be given to the intermodal relationships within larger transportation systems (land and sea). These analyses require the construction of complex, intricate and comprehensive system models" (NASA, 2002).

If the system-of-systems premise is adopted, then the design space in which solutions may be found is much more open. Infusion of new technology into the existing infrastructure organization is but one possibility; a reorganization of how new, improved and existing systems interoperate is also an alternative. However, existing analysis methodologies and tools, developed for systems, can only bring us so far, and thus new approaches are required to fully examine new solution sets. Further, the system-of-systems perspective expands the problem boundary to fully include areas such as policy and economics-public and private interest groups must be examined together along with the networks that connect them. Altogether, creating complex, intricate and comprehensive models requires first a new holistic framework so that problems within systems domains can be properly formulated and then solved by designers of aircraft, airspace and so forth. At the same time, results that flow from the system-of-systems framework must be concrete and actionable, targeted at identifying the research and development necessary to realize the most attractive transportation futures.

In sum, the pursuit of a desired, future national transportation system and a full comprehension of the preferred paths to guide this pursuit together represent a tremendous challenge, one that surely requires the wisdom and innovation of many. The essential ingredients at the start, however, are clear: effective frames of reference, thought processes and problem formulations. It is from this motivation that the present paper is written. The authors attempt to lay out a novel paradigm to address the challenge, starting from the idea that existing approaches are incomplete for the job is neither entirely new nor exclusive observations of the authors. Hence, the first part of this paper summarizes relevant research works indicative of the aerospace engineers' perspective, which then motivated the development of a broader intellectual construct. The second part formulates the transportation architecture and expresses the entities and their interaction dynamics in a generic, comprehensive manner. The final section presents initial results achieved through simulation and hypothesis of a more complete approach. The overall aim is to foster a generic, conceptual framework for the examination of air transportation architectures in the context of a larger National Transportation System (NTS), allowing problems to be recast so that today's designers can contemplate the future without preconceived boundaries.