This article focuses on issues regarding safety nets within A-SMGCS. A different point of view on evaluating the conflict alert function is presented. The given function is studied within the environment of continuation training of Air Traffic Controllers (ATCO) on 3D Tower simulator. During the exercises, the ATCOs are subjected to RWY incursion situations. The outcome is the proposal of methodology to be used to evaluate the performance of conflict alert function as well as the results of the evaluation itself. Conclusions regarding timing of alerts and performance of the conflict alert function as such are issued at the end.