Which of the following is NOT a visual system used to identify overhead powerlines?

Traffic cones are not a visual system specifically used to identify overhead powerlines. Instead, they are commonly used for traffic management and to indicate hazards or delineate areas for safety in various situations, but they do not serve the specific purpose of marking or highlighting overhead powerlines.

In contrast, tiger tails, warning signs, and powerline marker balls are all designed to make powerlines more visible to prevent accidents. Tiger tails are brightly colored materials that hang down from powerlines to alert individuals of their presence. Warning signs communicate the danger of nearby powerlines, while powerline marker balls, which are large, distinctive spheres, are placed on powerlines to enhance visibility, especially in areas where aircraft might be present. These systems are crucial for ensuring safety in environments where overhead powerlines are present, particularly around construction sites or in industrial areas.