A Review of Conflict Detection and Resolution Modeling Methods <s> CD&R System <s> An algorithm for detecting and analyzing potential enroute conflicts has been designed and implemented within the Center-TRACON Automation System (CTAS). The design uses the 4D trajectories provided by CTAS to produce a set of probable future conflicts, and assists the enroute sector controller in efficiently resolving these conflicts. Conflicts are detected via comparisons of trajectories at closely spaced time instants, with measures taken to limit the computations required to complete the search. Performance tests indicate more than 800 aircraft can be processed by the conflict detection and analysis algorithm within a search cycle of 10 seconds. This suggests that the search algorithm easily meets the performance requirements for an automated conflict detection and resolution tool in the current air traffic system. The algorithm includes a trial resolution functionality which automatically detects conflicts of proposed resolutions, and gives near instantaneous feedback to controller input. Field evaluation of the Conflict Probe will be conducted at the Denver and Fort Worth Air Route Traffic Control Centers (ARTCC) beginning in September, 1997. <s> BIB001 </s> A Review of Conflict Detection and Resolution Modeling Methods <s> CD&R System <s> In order to respond to rising demands for services from the National Airspace System (NAS), the Federal Aviation Administration (FAA) and The Mitre Corporation's Center for Advanced Aviation System Development (CAASD) have developed and evaluated a set of en route air traffic control (ATC) decision support capabilities based on many of years of earlier work on the Advanced En Route ATC (AERA) program. The component capabilities-embodied in a prototype referred to as the User Request Evaluation Tool (URET)-include a conflict probe that continuously checks current flight plan trajectories for strategic conflicts, and a Trial Planning function that allows a controller to expeditiously evaluate problem resolutions before they are issued as clearances. These capabilities are intended to provide the flexibility and decision support needed to allow more user preferences to be met while continuing to maintain or enhance today's level of safety. The URET prototype was deployed to the Indianapolis Air Route Traffic Control Center (ARTCC) for field trials in January 1996 and later expanded to include more sectors and to span longer periods of time. In addition, the prototype has been deployed and is being evaluated at the Memphis ARTCC. This paper presents key findings from the field trials and from other related activities. <s> BIB002 </s> A Review of Conflict Detection and Resolution Modeling Methods <s> CD&R System <s> A method to incorporate aircraft flight path intent information into a conflict detection and resolution system is described. The approach uses a set of probability density functions that describe potential trajectory errors such as cross-track, along-track, or course change, in a series of Monte Carlo simulations. The simulations are used to estimate the probability of conflict in traffic encounters. Intent information is readily included in the model, and can consist of a series of waypoints, heading or track holds, target altitudes, or maneuvering limitations from free flight concepts. The method also allows for direct incorporation of the confidence with which an intended path will be followed. An efficient modeling method is used that enables the Monte Carlo simulations to be run in real time, suggesting that such an approach could be used in conflict detection systems. Several example traffic encounters are discussed using conflict probability maps that show regions in which a conflict will likely occur. The potential benefit of access to intent information in a vertical conflict example is also shown. <s> BIB003
Alerting Thresholds using perf. metrics (false alarm, separation) Fig. 6 . Performance-based CD&R system design method Note that the same information elements are used to design the system in Figure 6 as are used in Figure 5 . The difference is only in the more direct application of that information in Figure   6 in the sense that surrogate metrics are no longer necessary. A limitation of the more direct approach, however, is that it requires real-time estimation of probabilities and must use reasonable probabilistic trajectory models. Probability estimation can be performed analytically or by running Monte Carlo simulations in near real time. These methods have been demonstrated in several applications, and should become even more viable as computational capabilities continue to increase BIB001 BIB002  BIB003 .