# Preliminary Impact Assessment of the Ad Hoc Separation Minima: A New Separation Mode
## 3 Methodology
### Capacity KPA  
Capacity focusses on the capability of a challenging volume of airspace to handle an increasing number of movements per unit of time through changes in operational concept and technology [38]. En-route capacity is analyzed in this study and is commonly estimated using Fast Time Simulations (FTS), employing models based on the ATCO workload (WL). An in-depth analysis of the different models applied in European and North American countries for the capacity estimation is provided in [39]. CAPAN methodology [40] was used for capacity computation in this research. This methodology was developed by EUROCONTROL. The capacity is estimated from the WL values of the tactical ATCO (TC) by means of FTS, with the ATCO WL being expressed in time values. The ATCO WL threshold used to obtain the capacity value was 70%, a value commonly used by several countries, such as Spain, Italy, Portugal, and Norway. Therefore, the capacity calculated with this threshold is equivalent to a WL of 42 min in one hour (70%). To calculate the ATCO WL, FTS are performed in RAMS software [41]. For this purpose, a 24H traffic sample (FPL trajectories, i.e., not modified by ATCO interventions) is used, which is cloned repeatedly to obtain different traffic situations in the sector. The ATCO WL is calculated on an hourly basis from the times associated with the different tasks assigned to the ATCO. These times were obtained from [42] and are detailed in Appendix A. The RAMS software simulates the real behavior of the sector and provides values for the tactical ATCO (TC) and planner ATCOs (PC) WLs. The capacity is calculated from the intersection of the curve representing the ATCO WL (found by regression) and the threshold value of 70%. For the capacity computation, different days of the busy week (the one containing the busy day) were simulated in RAMS, determining the ATCO WL for each hour of each of the days. Three scenarios were considered for the capacity study: the Baseline Scenario, Scenario 1 and Scenario 2. * Baseline Scenario: current scenario in which the horizontal separation minimum value is fixed and corresponds to a value of 5 NM (current value). * Scenario 1: scenario where the concept of Ad Hoc separation is implemented and the ASMT tool is available for the ATCO. However, this tool only includes the Ad Hoc separation determination functionality for each aircraft pair, not the CD&R functionality. * Scenario 2: scenario in which the concept of the Ad Hoc separation is implemented and the ASMT support tool is available, which includes, among its functionalities, the CD&R. A key assumption regarding the capacity computation in a scenario in which the concept of Ad Hoc separation is implemented is the issue that the ATCO WL could change. From the point of view of separation management, the concept of Ad Hoc separation could seem more complex. Nevertheless, it is assumed that whenever this concept is implemented, the ATCO will have a support tool that displays the ADSM to be applied (ASMT). Moreover, this tool includes advanced CD&R functionalities. Therefore, the ATCO WL could be maintained or even reduced (as a consequence of these advanced functionalities). The number of _LOS_ decreases because of reducing separation minima. That is, _LOS_ that could occur with a separation value of 5 NM, now, with Ad Hoc separation, may not \begin{table}
\begin{tabular}{c c c} \hline \hline
**KPA (SESAR)** & **PI** & **Units** \\ \hline \multirow{3}{*}{**Environment**} & CO\({}_{2}\) emissions reduction per _LOS_ saved & Kg \\  & Fuel reduction per _LOS_ saved & Kg \\  & Flown distance reduction per _LOS_ saved & NM \\ \hline \hline
**Airspace User** & & \\
**Cost-Efficiency** & Strategic Delay reduction per _LOS_ saved & Minutes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._occur (_LOS_ saved). The ATCO time associated with each of these _LOS_ saved (detection and resolution tasks), which translates into ATCO WL, should then not be considered. This would result in a new ATCO WL, and therefore a new capacity value (Scenario 1).