Mysterious orange and white balls situated on power lines across the United States have a crucial safety purpose: making the lines visible to pilots, particularly in areas near airports. These markers, often observed on taller power lines, are designed to prevent aviation accidents.
According to Professor Rui Bo of Missouri University, writing for The Conversation, the orbs function as prominent warning signs in the sky. "They’re like bright warning signs in the sky, protecting pilots, passengers and people on the ground below," Bo explained. Power lines, he noted, can easily blend into the surrounding landscape of homes and trees, creating a hazard for pilots flying at low altitudes during approaches and departures.
The balls themselves are not electrified. They are constructed from insulating materials such as plastic or fiberglass, which allows them to withstand outdoor conditions for 10 to 15 years. Their characteristic orange color is intentionally chosen for high visibility to pilots. Each ball is approximately the size of a large beach ball and weighs around 25 pounds. They are typically manufactured in two halves that are then assembled on the power line.
Installation of these markers can be a complex process, especially for very high power lines. Specialized teams, sometimes utilizing helicopters, are required for the task. During installation, the power lines remain energized, meaning high voltages of electricity continue to flow through them. For lower lines, installation crews can use bucket trucks. However, for higher lines, crews must work from a hovering helicopter to attach the two-halved marker to the wire.
While they require little maintenance, utility companies conduct periodic inspections to check for significant cracking or fading. Most residential power lines are not tall enough to necessitate the installation of these visibility markers.