The role of PF-TO in restricting the risk is however limited when PF-TX is not actively monitoring the traffic situation.
The comparison of cases with and without active traffic monitoring by ATCo-R indicate that in most cases, the controller's observation does not significantly restrict the risk.
The Monte Carlo simulations make it possible to understand the potential of agents in restricting the risk in off-nominal scenarios, through capturing their stochastic nature.
Only in cases without active monitoring of PF-TO and at the same time with active monitoring of PF-TX, do alerts restrict the risk by higher factors.
The results suggest that if PF-TX is not actively monitoring the traffic situation, then the conditional collision risk is high, and then the role of PF-TO, ATCo-R, and alerts in restricting the risk is rather limited.
To better understand the potential of agents to restrict the risk in cases where the performance of other agents is affected, one or more agents can be placed out of the monitoring role in the Monte Carlo simulations.
However, if the PF-TX is out of the monitoring role, the contribution of ATC alerts in restricting the risk is reduced to a factor of 1.9 and 4.2 for the cases C13 versus C14, and C15 versus C16 respectively.
This way the role of ATC alerts in restricting the risk becomes clearer in cases where the controller is not actively monitoring the traffic situation visually (e.g. cases C3, C7, C11, and C15).
The role of each agent is explained below: The results show that an actively monitoring PF-TX restricts the risk in cases where the performance of one or two agents is affected (cases C1 to C7).
This indicates that an active monitoring of PF-TO considerably restricts the risk in cases that involve both the lack of monitoring of ATCo-R, and malfunctioning of ATC alerts (Case C4 versus C8).
