Right of Way in the Sky: Two Problems in Aircraft Self-Separation and the Auction-Based Solution
Erev, Ido, Barron, Greg, Remington, Roger, Human Factors
Recent developments in aviation technology significantly improve the information available to pilots and the possibility of communication between aircraft (e.g., Livack, McDaniel, Battiste, & Johnson, 1999). In the near future, equipment will be available commercially that will allow aircraft to connect to air traffic control central computers and receive an updated picture of their location and the air traffic around them. The expected availability of this technology has led the U.S. Federal Aviation Administration (FAA) to consider changing current flight regulations to take advantage of the potential increases in efficiency afforded by this new technology (see National Civil Aviation Review Commission, 1997; Radio Technical Commission for Aeronautics [RTCA], 1994; Wickens, Mavor, & McGee, 1997). Among the options being investigated are changes to the rules that determine who is responsible for maintaining adequate separation between aircraft and who should maneuver to avoid potential conflicts (RTCA, 1994).
In current air traffic operations, ground-based air traffic controllers have the responsibility for maintaining separation as well as the authority to vector aircraft to avoid separation violations. Pilots fly in accordance with air traffic control instructions regarding airspeed, altitude, and heading, unless such instructions pose a direct threat to the aircraft. In effect, air traffic control acts as a noncompetitive entity within the competitive air carrier environment, in which the principal concern is the safe operation of the national airspace. The changes under consideration would replace the centralized oversight provided by air traffic control with a decentralized decision-making system. Individual aircraft could freely choose fuel- or time-optimized routes, instead of being routed along fixed airways, as is the typical case today. This general concept has been termed free flight and is the subject of intensive investigation by the FAA, the National Aeronautics and Space Administration (NASA), and various industry and academic research efforts (e.g., the Advanced Air Transportation Technologies program).
One change envisioned under free flight is the transfer of responsibility for separating aircraft from ground-based air traffic control to individual aircraft, a concept referred to as self-separation. Under self-separation, aircrews would be alerted to potential conflicts and be responsible for choosing maneuvers that would resolve them. Two implementation approaches have been investigated: (a) communication between conflict aircraft to negotiate a solution maneuver (e.g., Livack et al., 1999; Lozito et al., 2000) and (b) "right-of-way" rules that would determine which aircraft should maneuver. Proposed right-of-way rules rely on existing regulations in effect today under visual flight rule conditions. Visual flight rules are in effect for flight operations outside of terminal control areas conducted under visual conditions that afford good visibility. These rules state that when two aircraft are in potential conflict (i.e., continuing on the current trajectories would lead to a separation violation), the right of way goes to (a) the aircraft that comes from the right or, in cases of overtaking, (b) the aircraft in front. Whereas these right-of-way rules have been found to be very useful for many years, their effectiveness when applied to the entire airspace has yet to be demonstrated. Likewise, negotiating an avoidance maneuver sounds reasonable but is largely untried.
The development of new, efficient rules requires good understanding of the technological and economic constraints and of the expected behavior of future users. It is of particular importance to try to understand the possible long-term adaptation of users to the new rules. Failure to do so can lead to unintended consequences that may be inefficient or potentially dangerous. However, existing methods make it difficult to assess long-term adaptation. …