Visual search in complex displays: Factors affecting conflict detection byair traffic controllers

Recent free flight proposals to relax airspace constraints and give greater autonomy to aircraft have raised concerns about their impact on controller performance. Relaxing route and altitude restrictions would reduce the reg ularity of traffic through individual sectors, possibly impairing controlle r situation awareness. We examined the impact of this reduced regularity in four visual search experiments that tested controllers' detection of traff ic conflicts in the four conditions created by factorial manipulation of fi xed routes (present vs, absent) and altitude restrictions (present vs, abse nt). These four conditions were tested under varying levels of traffic load and conflict geometry (conflict time and conflict angle). Traffic load and conflict geometry showed strong and consistent effects in all experiments. Color coding altitude also substantially improved detection times. In cont rast, removing altitude restrictions had only a small negative impact, and removing route restrictions had virtually no negative impact. In some cases conflict detection was actually better without fixed routes. The-implicati ons and limitations of these results for the feasibility of free flight are discussed. Actual or potential applications include providing guidance in the selection of free flight operational concepts.