*2.1. Methodology*

This subsection summarises the methodology followed throughout the study, from the first steps taken to setup the simulation platform to detailed analysis of the event combinations and their influence on the taskload and subjective workload of ATCOs. The methodology followed in this study can be seen in the form of a flow chart in Figure 1. Four stages have been defined:


**Figure 1.** Methodology to follow to obtain an event-based taskload profile of reference and to study ATC events and their combinations.

Before simulations could be performed, several preliminary steps had to be taken. First, the simulation platform was configured. Subsequently, the ATC events that would serve as the basis for exercise design were defined. For this first stage of the project, a total of four exercises of increasing difficulty were designed. When events were introduced at specific moments of the exercise, a unique designed taskload profile was obtained for each of the exercises.

Once the exercises had been designed, the next step was to develop the simulation campaign. In total, six participants participated in the simulations. Each of them simulated each of the four exercises. Several data were recorded during the development of the exercises.

For this line of research, the data of interest were the video recordings of the simulations, which provided information on the actual events and actions carried out by the participants, and subjective workload assessment data. For this purpose, the Instantaneous Self-Assessment (ISA) method was implemented in the simulator through the use of a window that appeared on the radar screen every two and a half minutes to ask participants to evaluate their perceived workload.

The ISA method is based on the idea of asking the operator to assess their workload at regular intervals. At each assessment, the operator is required to select a value on a scale of 1–5. On this scale, 1 means under-utilised and 5 means excessively busy [18]. The ISA method was chosen because it is considered less intrusive than other subjective workload assessment methods [19]. Furthermore, it can be run during the progression of exercises.

The first objective was to find an event-based taskload baseline. In fact, the ultimate goal was to create a profile with the taskload values for each minute of the simulation.

When the exercises were created, a designed taskload profile was defined. Therefore, the first question to be solved is whether this designed taskload can be used as a reference. This question is represented by the diamond in Figure 1. There are two options: 'yes' and 'no'. The first option is to demonstrate that the answer is 'yes'. This would be the simplest possible situation. In that case, since the designed events of the simulations are known in advance, the designed taskload profile could be used directly as a reference when studying the evolution of neurophysiological variables.

The other alternative is that the answer to the question is negative. If it is not possible to use the designed taskload profile as a reference, it will be necessary to establish a methodology for obtaining a better reference based on the events that actually took place during the development of the simulations before addressing the second objective of the study and moving towards analysis of the events and their relationship with the recorded subjective workload values.
