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The primary purpose of the research on Separation Assurance in the Airspace Operations Laboratory is to gather more insight into the fundamental problem of human/automation integration and allocation of roles and responsibilities required to achieve the significant capacity increases targeted for the Next Generation Air Transportation System (NextGen). Initial part-task studies with controllers in the loop on this research topic have been conducted in the Airspace Operations Laboratory since August 2007. These studies specifically begin to investigate the future role of air traffic controllers and automation in a service provider-based automated separation assurance environment. The focus is on trajectory-based operations at double and triple the traffic density of today's airspace system. An introduction to this research area is also provided in the movie on effective human/automation cooperation on this website


Air traffic demand is anticipated to grow substantially in the coming decades. The Federal Aviation Administration (FAA) and industry forecast that air traffic operations are expected to increase 150 to 250 percent over the next two decades. Analyses of even the most conservative growth estimates show a significant lack of existing and planned capacity.

It is assumed that managing 2 or 3 times today's traffic density requires a fundamental change from today's operations in how separation between aircraft is assured. In today's very safe system, air traffic controllers take active control over each aircraft in their airspace and issue clearances to keep it separate from other traffic, expedite traffic flows, and provide additional services, workload permitting. Being actively involved with each individual aircraft provides the awareness required to detect and resolve potential losses of separation independent of automated aids. However, this manual process can only be performed for a very limited number of aircraft. In recognition of this fact, each airspace sector today has a defined maximum number of aircraft that are allowed to enter. This constraint exists as a way of ensuring that the demands on the cognitive resources of the air traffic controller(s) controlling this sector are not exceeded. Figure 1 below depicts an air traffic controller display contrasting a typical current day high traffic density to twice and three times this density. Assuming that the display on the left represents the limit of the sustained traffic load a controller can comfortably manage today; operations need to change significantly for the move to the traffic levels depicted in the center and on the right to be realized.

Figure 1. Current day controller display with 1x, 2x and 3x traffic. 2x and 3x cannot be managed with conventional air traffic control techniques.
Figure 1: Current day controller display with 1x, 2x and 3x traffic. 2x and 3x cannot be managed with conventional air traffic control techniques.


NextGen envisions trajectory-based operations (TBO) to replace clearance-based operations in many parts of the airspace. New automated separation assurance functions are intended to help overcome the aforementioned limitations of controllers in manually maintaining safe separation between aircraft. The two primary new separation assurance concepts are airborne self-separation and ground-based automated separation assurance. Research is ongoing in both areas. Between 2002 and 2004, NASA researchers, including the researchers in the AOL were part of human-in-the-loop assessments of mixed operations with airborne self-separation at more than two times today's traffic density.

In late 2006 the AOL team started implementing the latest ground-based conflict resolution technologies developed under the guidance of Heinz Erzberger in NASA Ames' Aviation Systems division. At the same time new display prototypes were developed in the AOL that reflect the shift in roles and responsibilities from the human to the automation and are designed to enable managing the extreme traffic density that is envisioned for NextGen. An example prototype is depicted below for the same traffic situation that can be seen on the 3x display above and on the right.

Controller display prototype for managing higher traffic levels with advanced automation
Figure 2: Controller display prototype for managing higher traffic levels with advanced automation. All low-lighted aircraft are managed by the ground-based separation assurance automation. The controller manages the highlighted aircraft in the same airspace.

Today the AOL represents one of the very few -if not the only- laboratory that can simulate the full range of near-, mid- and far-term separation assurance functions from current day air traffic control via integrated decision support functions to fully automated separation assurance. All capabilities are integrated into realistic controller and pilot workstations and can be turned on or off by the researchers via setup panels. The ground automation is fully interoperable with current day and advanced flight decks that participate in the simulation within the AOL or simulation facilities that are networked with the AOL.

Click to download the complete Separation Assurance research report Download the full Separation Assurance Synopsis(PDF- 1.1MB)


P. Kopardekar, T. Prevot and M. Jastrezebski (2008) "Complexity Measurement Under Higher Levels of Automation and Higher Traffic Densities" Air Traffic Control Quarterly (in preparation)

Prevot, T., Homola J. and J. Mercer (2008) "Initial Study of Controller/Automation Integration for NextGen Separation Assurance" AIAA-2008-6330 AIAA Guidance, Navigation, and Control Conference and Exhibit 18 - 21 August 2008, Honolulu, Hawaii

Prevot, T., Homola J. and J. Mercer (2008) "Human-in-the-Loop Evaluation of Ground-Based Automated Separation Assurance for NextGen" ICAS 2008-11.4.5, 6th International Congress of the Aeronautical Sciences (ICAS), and AIAA-ATIO-2008-8885, Anchorage, Alaska, Sept 15-19, 2008

Point of Contact: Thomas Prevot, Dr. -Ing., San Jose State University/NASA Ames Research Center
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Curator: Phil So
NASA Official: Everett Palmer
Last Updated: June 22, 2012