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The Collaborative Routing Coordination Tools, or CRCT, is an integrated collection of automation functions to assist traffic flow management in monitoring traffic flows, developing strategies to alleviate congestion and avoid severe weather, and analyzing the impact of proposed strategies. With the CRCT analysis capabilities, the traffic manager is able to visualize the impact of a proposed strategy on sector loading or on individual aircraft, and compare the potential effects of each strategy. Eventually, the traffic manager will be able to share this information not only with traffic managers from other facilities but also with airspace users. Thus, CRCT capabilities will help facilitate collaboration among National Airspace System (NAS) stakeholders to develop strategies that are most suitable for meeting their respective operating objectives when constraints in the NAS require traffic flow management action.

CAASD's laboratories were the site for the initial development and evaluation of the tools that became known as CRCT. Constructed to evaluate the implications on the NAS of the Free Flight concept (especially on air traffic controllers and traffic flow managers), the tools evolved with the guidance of operational personnel at the Kansas City Center where an early version of CRCT was located for feedback purposes.

Developed by the Center for Advanced Aviation System Development (CAASD) at The MITRE Corporation as part of its Traffic Flow Management Research and Development activities, CRCT currently exists on a research platform on which operational concepts and automation functions are developed in CAASD's laboratory and evaluated by traffic flow management personnel in their operational facilities. As a result of these evaluations, operational needs for capabilities are identified, desired capabilities are refined, and procedures for operational use are developed. When the Federal Aviation Administration (FAA) determines that a capability should be integrated into the Traffic Flow Management System, CAASD assists the FAA in transferring the technology to the implementation team and, where appropriate, the private sector.

With focused research efforts begun by CAASD in 1996 (and building on more general research at CAASD over the previous decade), CRCT has been developed for the purpose of providing tools to traffic flow managers and airspace users to address the shortfalls experienced in the present system. Specifically, CRCT functions are designed to assist with the following:

• Visualizing future traffic flows, based on filed flight plan information.
• Identifying and analyzing potential traffic flow management situations.
• Identifying the flights that are expected to be directly impacted by the situation.
• Defining candidate routes (either for traffic flows or specific flights) to alleviate the situation.
• Analyzing the impact of a reroute strategy on sector loading for all the sectors across a region.
• Enabling traffic flow managers from all facilities and airspace users to gain common situational awareness and information about strategy alternatives.
• Facilitating the implementation of reroute strategies.

Roles of Air Traffic Control and Traffic Flow Management

In air traffic control, separation assurance is a service provided by air traffic controllers. Controllers work with flights one-on-one to ensure every single aircraft remains at safe distances from all other aircraft and from designated airspace. On the other hand, traffic flow management, which is performed by traffic flow managers, works with aircraft populations that together build the traffic flows from city-to-city and region-to-region. As traffic levels increase, traffic flows become more complex and traffic flow management actions (because of weather avoidance, reduced capacity at some major airport, or a myriad of other reasons) can affect more flights. The greater the number of aircraft affected, and the frequency of traffic flow management actions, the greater the probability that traffic flow management actions become costly to the users of the airspace, for example, in added distance or time per flight, inefficient altitude or route assignments, or ground holds. On the other hand, the user costs of actions must be balanced with the primary need to maintain safety of the system. This balancing is the key job of traffic flow management. The complexity of the current and future traffic flow management task drives the need for automation assistance which, in turn, will enable the multi-party collaboration needed to solve traffic flow management problems safely and cost-effectively.

The Need for Traffic Flow Management Tools

Personnel at the Kansas City Air Route Traffic Control Center evaluate the most recent installation of CRCT capabilities. The CRCT effort is the result of more than a decade of research and development aimed at meeting the needs stated by airspace users and traffic flow managers since the mid-to-late 1980s. These needs have the common theme of "collaboration:" airspace users and service providers need to collaborate on traffic flow management strategy and decisions to ensure the aviation system runs smoothly and efficiently.

When the availability of airspace is reduced—because of severe weather or loss of a navigational aid, for example—or when airspace is congested, traffic flow management is responsible for taking action to balance demand for airspace with the capacity of the airspace without compromising safety. Such actions often involve requesting flights, whether in the air or yet to depart, to fly another route than had been planned by the dispatcher or flight planner. Although rerouting is a common strategy, traffic managers today develop reroutes with limited information being available on how moving traffic to other airspace affects sector volume and, hence, the en route center's ability to manage the additional traffic or the changing traffic patterns. Likewise, because users' operating constraints, preferences, and objectives are not apparent from the filed flight plan, traffic managers develop reroute strategies without benefit of a clear understanding of an airspace user's operational constraints or preferences.

Traffic managers today lack the necessary tools to accurately forecast demand, visualize the future demand, quickly evaluate how well a proposed strategy works, or share situational awareness or strategy information with other operational facilities or the airspace users. In particular, lack of common situational awareness often leads to second-guessing, and, in the case of the airspace user, being reactive rather than proactive in managing its fleet of aircraft to the constraints of the NAS. With common situational awareness, airspace users or FAA operational facilities could take actions that reduce demand for congested airspace (through changing flights' routes or altitudes, delaying departures, or , in the case of a user, canceling flights all together) — thus, either obviating the need for major traffic management actions or reducing their severity. Therefore, airspace users are able to make decisions that better fit their economic and operational objectives and FAA facilities can take actions that complement other situations they may be addressing.

From the late 1980s to the early 1990s, the FAA convened the Traffic Flow Management-Architecture and Requirements Team to define the future traffic flow management system to overcome these shortfalls. Composed of leaders from industry and the FAA, the TFM-ART articulated the need for traffic flow management to become more collaborative—to become more information-driven, to share information, to develop joint strategies and action—since decisions and actions affecting traffic flows could affect airline costs and competitiveness. The TFM-ART's report emphasized the need for collaboration and provided the framework for future research.

CRCT Features

To speed up the development of the CRCT prototype, existing CAASD modeling and simulation capabilities were used whenever feasible (click on images below for larger version)..

Current major CRCT capabilities include the following:

NAS Monitor — displays the alert status of the 20 Air Route Traffic Control Centers (ARTCCs) in the contiguous United States.

The CRCT NAS Monitor and NAS Sector Demand capabilities were created as a result of one of the requests from the FAA that initiated CRCT research: Develop capabilities that improve upon the FAA's existing Monitor Alert function. An especially useful tool for national TFM, the CRCT NAS Monitor display enables the traffic flow manager to quickly identify those en route centers expected to experience traffic levels that exceed their sectors' thresholds. For example, in this display, according to currently filed flight plans, Jacksonville Center (ZJX) is expected to have one sector in red alert (when the number of active flights exceeds the sector threshold) in the 17:45-17:59 time frame, two sectors in yellow alert (when the total number of active and not yet departed flights exceeds the sector threshold) in the 18:15-18:29 time frame, and one sector in red alert and two sectors in yellow alert in the 18:00-18:14 time frame. By using the computer mouse to click on a specific entry in the NAS Monitor display, additional information can be obtained, such as which specific sectors in ZJX are alerted as well as the number of active and not yet departed flights exceeding the sector threshold. This mouse action would activate the NAS Sector Demand capability described below.

NAS Sector Demand — provides sector count projections for several hours in the future for each of the 20 ARTCCs:

For example, projected loading for each of the sectors of Indianapolis Center (ZID) is depicted for the next four hours. In particular, based on filed flight plan information, the number of flights that are currently airborne is expected to overload sector 81 during the 18:15-18:29 time period (a red alert because the number of airborne flights exceeds the normal capacity of sector 81, 12 aircraft), while a combination of currently airborne and not-yet-departed flights is expected to exceed sector 82's threshold from 20:30-20:44 (a yellow alert because the traffic load that exceeds the normal capacity includes flights that have not yet departed).

Traffic Flow and Demand Analysis — identifies flights that are planned to operate through a defined airspace and characterizes the demand on that airspace.

The traffic flow manager can analyze the traffic through any airspace by defining a three-dimensional Flow Constrained Area (FCA) around the airspace on the CRCT display and specifying the time period for which the FCA is active. The airspace being analyzed can have predefined boundaries, such as a sector or Special Use Airspace, or can be drawn ad hoc to fit the situation, such as a severe weather system. In this case, the Kansas City Center (ZKC) traffic flow manager has defined Sector 2 as an FCA because CRCT has indicated that this sector is expected to be congested from 20:30 to 22:30. CRCT depicts the routes of those flights that have been planned to transit Sector 2 during this time period.

CRCT lists flight information for each of the flights expected to transit the active FCA.

Aircraft Reroute Definition — permits graphical or textual definition of reroutes for a group of flights or for individual flights.

Using CRCT, the traffic flow manager is able to propose reroutes in several ways. Here, the traffic manager uses the computer mouse to create a reroute to the east of Sector 2 for a group of north-south flights. The proposed reroute strategy has these flights continuing on the remainder of their filed routes.

CRCT displays the route specification for each flight affected by the proposed reroute and also estimates the difference in time and nautical miles flown if the flight were replanned as proposed. These estimates take the wind effects into account.

Reroute Evaluation — permits evaluation of the potential impacts of reroutes on sector volume, spacing, and traffic density.

The traffic flow manager can develop several reroute proposals, then compare the results. Here, the traffic flow manager is studying the sector loading for Memphis Center (ZME) that would result if the reroute proposal "Reroute Set 3" were implemented. Those sectors outlined in light blue would experience a decrease in loading, while those outlined in dark blue would experience an increase. In addition, CRCT can also be used to evaluate reroutes by using the Future Traffic Display to examine resulting spacing and density.

Web-based Sharing of CRCT Information — permits operational facilities and airspace users to view CRCT information on the Command Center Web page. Typically, a traffic flow management action involves the coordinated efforts of traffic flow managers in several facilities. Web-based sharing is an inexpensive way to allow all the stakeholders, both FAA and airspace users, to share the information equally.

Getting CRCT to the Field

During the last two years, CRCT has been installed for evaluation purposes at Kansas City Center and the Air Traffic Control System Command Center (the facility responsible for national traffic flow management), and will continue to be evaluated by traffic flow managers over the next several months. The FAA and CAASD are jointly conducting these evaluations. Later this year, CRCT will be installed in the Indianapolis Center to enable a broader evaluation. CRCT functionality has benefited greatly from past field evaluation efforts and, with input from ongoing exercises and evaluations, continues to evolve. The purpose of the current set of evaluations is to validate the local and national traffic management requirements for CRCT capabilities that will be implemented in the NAS as part of the FAA's Free Flight Phase 2 program. These validated requirements will serve as the basis for technology transfer of CRCT to the FAA's implementation team.

A view into the Air Traffic Control System Command Center in Herndon, Virginia, where CRCT was installed for operational evaluation in May 2000. The Command Center coordinates the activities of traffic managers among the different FAA operational facilities (en route centers and terminals), and also provides the leadership to plan traffic management actions when confronted with major events such as reduced capacity at a major airport or a weather system over several en route centers.

CRCT is being used for analysis purposes by CAASD personnel at the Air Traffic Control System Command Center to support the FAA's Spring 2000 initiative.

Future Plans

CAASD is researching and developing new capabilities that have high potential to deliver additional operational benefits when combined with the initial CRCT capabilities. For example, development of capabilities to model Miles-in-Trail (MIT) restrictions and to assess their impact, in concert with rerouting and ground delays, is being given high priority based on user feedback. Also, research is being conducted on computer-assisted resolution support to reduce time and workload involved in providing equitable resolutions. The FAA and CAASD are preparing for field evaluations of these new features.

In addition, CAASD is working with the FAA on transferring the technology associated with a desired CRCT capability (for example, FCA application and trajectory modeling algorithms) to the FAA's implementation team responsible for integrating the CRCT capability into the Traffic Flow Management System.

Flow Constrained Area Advisory Enabled by CRCT

The Federal Aviation Administration's Air Traffic Control System Command Center (ATCSCC) in Herndon, Va., published the first ever flow constrained area (FCA) advisory on April 23. FAA personnel conducted two weeks of intensive training on when to implement an FCA at the facilities. FCAs are part of the strategic planning process for events occuring in the national airspace system (NAS) that are anticipated to last 90 minutes or longer. The Ft. Worth air route traffic control center (ARTCC) submitted the April 23 FCA, encompassing the Ft. Worth and Memphis centers, because of severe thunderstorms impacting en route traffic.

The publication of this advisory is an important milestone in the evolutionary transfer of CAASD's collaborative routing coordination tools (CRCT) technology to the FAA. CRCT is being integrated with the existing Enhanced Traffic Management System functional capabilities and the Traffic Situation Display human computer interface. The FCA capability and the rerouting capability (to be deployed this fall) of CRCT are the first two components to be transferred to the FAA.

Many people in CAASD have worked hard toward the success of transferring and implementing CRCT technology. Laurel Rhodes (F045) and Dusty Rhodes (F068) conducted extensive evaluations before the technology transfer process could begin. Project Team Managers Kelly Connolly and Alex Alshtein (F045), along with Norma Taber (F045) and Rafe Katkin (F042) are supporting the actual piece by piece transfer of CRCT. Finally, Mark Huberdeau (F064), Elliott Simons (F045) and Jack Brennan (F068) conducted the testing of transferred CRCT capabilities at the ATCSCC that validated the use of the procedures.

Why create a flow constrained area?

FCAs are designed to evaluate and alleviate potential adverse effects to the FAA and users during periods when events have a significant impact on the NAS. The FCA is one of several initiatives that have been underway to improve NAS performance through "collaborative decision making." Not only does it provide a mechanism of automated data transfer, it enables a common situational awareness to air traffic personnel and NAS users. For example, when an FCA is implemented, CRCT allows traffic flow managers (TFMs) to generate a list of the aircraft that are scheduled to navigate through that area. Airlines can be notified of the expected reduction in traffic in the FCA and airline dispatchers can then keep their aircraft out of that area when filing flight plans.

How does it work?

Using CRCT's Traffic Flow and Demand Analysis capability, TFMs can identify flights that are planned to operate through a defined airspace and characterize the demand on that airspace. The TFM defines a three-dimensional FCA around the airspace on the CRCT display and specifies the time period for which it will be active. The airspace being analyzed can have predefined boundaries, such as a sector or Special Use Airspace, or can be drawn to fit a specific situation. Once the FCA is specified, CRCT lists flight information for each of the flights expected to transit the active FCA. At this point, the TFM makes the decision as to whether or not to submit the proposed FCA to the command center.

The ATCSCC monitors and manages the flow of air traffic throughout the NAS with the goal of producing a safe, orderly, and expeditious flow of traffic while minimizing delays. It also serves as the focus of collaborative decision making by the FAA and industry. If ATCSCC specialists concur that an FCA should be created, they make it "public" by sending an advisory and then plan strategies during the next strategic planning team teleconference. (Teleconferences take place every... how often?) The strategic planning team is a key component of the collaborative decision-making process and it includes the ATCSCC, airline strategic planners, FAA field facilities, forecasters, military, international facilities and general aviation.

Date Posted: July 18, 2007