Benefits of direct-to tool in National Airspace System

Initiatives in air traffic management both in the United States and in Europe are aimed at providing air traffic controllers with automation tools to separate traffic, meet time constraints required for traffic flow and accommodate route preferences of users such as airlines. These efforts are expected to result in removal of restrictions on users preferred routes without compromising safety. Thus, aircraft will be able to fly optimal routes such as great circle and wind-optimal routes. NASA has developed the design for a new automation tool, referred to as the direct-to tool, which advises the controller on direct time-saving routes for any aircraft irrespective of levels of equipage. In contrast to earlier studies on the potential benefits of direct routes in the National Airspace System, the objective of the paper is to evaluate the benefits based on a controller tool. The paper describes the benefits of applying this algorithm to the 20 air route traffic control centers within the United States. Benefits are measured in terms of the total time savings accrued by flying the direct route. Results are described for three different implementations dependent on the search region bounding each air route traffic control center. The first region exactly encloses the air route traffic control center airspace, the second is the smallest rectangular bounding region while the third is a bigger rectangular bounding region approximately twice as large as the second region. It is shown that the application of the direct-to routing algorithm does not significantly alter the number of conflicts and their spatial distribution compared to the case in which the aircraft fly along the airways. The results presented in the paper suggest that the direct-to routing algorithm can provide significant cost savings to the users without adversely impacting the air traffic management functions