Solution-Space-Based Complexity Analysis of the Difficulty of Aircraft Merging Tasks

Abstract

Air traffic controller workload is considered to be a limiting factor in the growth of air traffic worldwide. In this paper a new method of assessing controller task demand load will be developed and tested. Based on the hypothesis that operator workload is primarily caused by the difficulty of the task to be conducted, the concept of the solution space is described. For any particular air traffic control problem, the solution space describes the constraints in the environment that limit (and therefore guide) air traffic controller decisions and actions. The difficulty of that particular control problem can then be analyzed by considering the properties of the solution space. The task of merging an aircraft into a stream of other aircraft that fly along a fixed route is considered. An experiment has been conducted in which subjects were instructed to solve several merging problem scenarios of varying difficulty. After completing each scenario, subjects were asked to rate the difficulty of their task. High correlations are found between several solution-space properties and self-reported task difficulty. Nomenclature A = area, % of available area B = bunching BW = band size, deg d = distance, length, m F = ratio of sample variances H = heading, deg N = number (as in number of aircraft) P = position, m ^ P = transposed position, m p = significance R = Pearson correlation coefficient S = separation minimum (for aircraft), m S = score S = mean score T = time, s t = time, s V = velocity, m=s Subscripts AC = aircraft a = approaching b = back c = correction com = command e = turn termination (point) e = evacuation (time) f = front (for interception velocity) G = ghost h = heading head = heading int = interception l = largest (area) min = minimum max = maximum rel = relative (velocity) rel = relevant (aircraft) SV = separation violations s = segment t = turn initiation (point) t = total (area) Z = Z (as in Z scores) = mean = standard deviation ! = angular velocity, rad=s

Solution-Space–Based Analysis of Dynamic Air Traffic Controller Workload

“…That is, the "area" of safe solutions in the SSD is strongly correlated to task complexity. Hermes et al [27] experimentally tested and confirmed this hypothesis, in a task where subjects merged one "free" aircraft in a stream of on-route aircraft. High correlations were indeed found between the initial solution space area and the subjective difficulty ratings.…”

“…Conclusions from previous work [27] stated that the area in the solution space that offers conlict-free solutions has a strong (inverse) correlation with ATCo workload. For this experiment, for each aircraft, the area of that aircraft's SSD that is covered by the CoZ's was calculated as a percentage of the total available area between the minimum and the maximum velocity constraints (of that aircraft) in the SSD.…”

“…Hermes et al [27] presented an approximated solution, modelling turns in an aircraft future route as straight segments -cutting the corner -replacing the curve by a straight route-segment that starts at the turn initiation point and that ends at the turn termination point. The observed aircraft is assumed to change its heading instantaneously at these two transition points, see Fig.…”

“…Exceptions are the work on complexity maps as proposed by Lee et al [25], the conflict-resolution taskload method as described in Vela et al [26], and the solution-space based approach of Hermes et al [27]. In Vela et al [26], workload is approximated using the number of resolution commands required to manage traffic in a sector, and optimization techniques are applied to reduce conflict resolution-related workload.…”

The Effect of Traffic Complexity on the Development of Near Misses on the North Sea

“…In terms of safety analysis, however, the human element adds to the complexity of the system. Several aviation-related studies propose that traffic complexity can be assessed in terms of traffic manoeuvrability, expressed in a solution space for each aircraft [6], [7]. This paper proposes a similar method for maritime traffic.…”