Figure 4.

Conflict event models A (A) and B (B). Algebraic symbols and equations specify the length of the path segments of the air routes (not drawn to scale) and their topological relationships. These routes were kept hidden from participants' view. Colored aircraft represent aircraft cruising on the same flight level while gray aircraft in the background represent aircraft cruising at flight levels different from that of the former cluster. On the same flight level, a non-conflicting aircraft in each model (colored in green) was placed initially at a safe distance away from the conflict zone, which is represented by the dotted circle with a radius of 5.0 nm. The total number of non-conflicting aircraft located in the vicinity of two conflicting aircraft that constituted each conflict event increased from one in the low air traffic density (ATD) condition to three and five in the medium and high ATD conditions, respectively (see text, for more details).