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“Cultural” issues regarding the introduction of new technologies (DSTs), procedures and roles/responsibilities; e.g., operational training and pilot/controller acceptance.
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Business issues that influence user decision-making regarding operational priorities.
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Information security issues related to access and/or exchange of user-proprietary data.
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Issues relating to NAS benefits arising from a reduction in separation standards.
2. EVOLUTION PATH TO DAG-TM
2.1 Issues, Concerns, and Opportunities in the National Airspace System
Many users of today’s aviation system believe that the current, relatively centralized mode of air traffic control / management creates excessive constraints on their operations, resulting in operational inefficiencies. The U.S. air traffic control system has evolved considerably from its birth in the 1920’s to today’s system; a description may be found in Refs. 3 and 4. Today’s system has evolved in response to the increase in traffic volume over the years. To deal with the increase in traffic volume, the Federal Aviation Administration (FAA) has employed several measures to prevent actual traffic levels from exceeding the human capabilities of the controllers who are responsible for the safe separation of traffic. These measures include airspace sectorization (to divide workload); airspace structure, procedures, and ATSP-preferred routes (to structure traffic flows and segregate aircraft); and flow restrictions (to prevent congestion from exceeding acceptable levels). The current system is considered to be technologically outdated and likely to bog down further as predicted traffic growth is realized. Without significant changes to the NAS, analysis indicates that predicted traffic growth will bring the system to gridlock by the year 2014 (Ref. 5). In fact, users are already experiencing significant losses due to inefficiencies. It has been estimated that scheduled air carriers alone lost $3.5 billion in direct operating costs due to delays in 1995 (Ref. 6). These delays and associated costs are noticeably greater today with the rapid growth of traffic in recent years. This has led to an effort within the aviation community to develop a more flexible system that increases capacity and allows the users to increase their operating efficiencies in ways that meet their own objectives. Users not only desire greater flexibility, but also less dependence on centralized air traffic control systems and infrastructure (to minimize their dependence on a government service and to maximize global interoperability). This loosely defined operational paradigm is commonly referred to as “Free Flight.”
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本文鏈接地址：Concept Definition for Distributed Air/Ground Traffic Management (DAG-TM)(8)
