Display dimensionality and conflict geometry effects on maneuver preferences for resolving in-flight conflicts

Rendezvous Under Temporal Uncertainty

OBJECTIVE

Three experiments sought to understand performance limitations in controlling a ship attempting to meet another moving ship that approached from various trajectories. The influence of uncertainty, resulting from occasional unpredictable delays in one's own movement, was examined.

BACKGROUND

Cognitive elements of rendezvous have been little studied. Related work such as the planning fallacy and bias toward underestimating time-to-contact imply a tendency toward late arrival at a rendezvous.

METHODS

In a simplified simulation, participants controlled the speed and/or heading of their own ship once per scenario to try to rendezvous with another ship. Forty-five scenarios of approximately 30 s were conducted with different starting geometries and, in two of three experiments, with different frequencies and lengths of the unexpected delays.

RESULTS

Perfect rendezvous were hard to obtain, with a general tendency to arrive late and pass behind the target vessel, although this was dependent on the angle of approach and relative speed. When occasional delays were introduced, less frequent but longer delays disrupted performance more than shorter but more frequent delays. Where delays were possible, but no delay occurred, there was no longer evidence of a general tendency to more frequently pass behind the target ship. Additionally, people did not wait to see if the unpredictable delays would occur before executing a course of action. Different control strategies were deployed and dual axis control was preferred.

CONCLUSIONS

The tendency to arrive late and the influence of the possibility of uncertain delays are discussed in relationship to control strategies.

Comparing two types of engineering visualizations: task-related manipulations matter

This study focuses on the comparison of traditional engineering drawings with a CAD (computer aided design) visualization in terms of user performance and eye movements in an applied context. Twenty-five students of mechanical engineering completed search tasks for measures in two distinct depictions of a car engine component (engineering drawing vs. CAD model). Besides spatial dimensionality, the display types most notably differed in terms of information layout, access and interaction options. The CAD visualization yielded better performance, if users directly manipulated the object, but was inferior, if employed in a conventional static manner, i.e. inspecting only predefined views. An additional eye movement analysis revealed longer fixation durations and a stronger increase of task-relevant fixations over time when interacting with the CAD visualization. This suggests a more focused extraction and filtering of information. We conclude that the three-dimensional CAD visualization can be advantageous if its ability to manipulate is used.

False alerts in air traffic control conflict alerting system: is there a "cry wolf" effect?

OBJECTIVE

The aim is to establish the extent to which the high false-alarm rate of air traffic control midair conflict alerts is responsible for a "cry wolf' effect-where true alerts are not responded to and all alerts are delayed in their response.

BACKGROUND

Some aircraft collisions have been partly attributed to the cry wolf effect, and in other domains (health care and systems monitoring), there is a causal connection between false-alarm rate and cry wolf behavior. We hypothesized that a corresponding relationship exists in air traffic control (ATC).

METHOD

Aircraft track and alert system behavior data surrounding 495 conflict alerts were analyzed to identify true and false alerts, trajectory type, and controller behavior. Forty-five percent of the alerts were false, ranging from 0.28 to 0.58.

RESULTS

Although centers with more false alerts contributed to more nonresponses, there was no evidence that these were nonresponses to true alerts or that response times were delayed in those centers. Instead, controllers showed desirable anticipatory behavior by issuing trajectory changes prior to the alert. Those trajectory pairs whose conflicts were more difficult to visualize induced more reliance on, and less compliance with, the alerting system.

CONCLUSION

The high false-alarm rate does not appear to induce cry wolf behavior in the context of en route ATC conflict alerts.

APPLICATION

There is no need to substantially modify conflict alert algorithms, but the conflict alert system may be modified to address difficult-to-visualize conflicts.