Check out the video below from T&D World to see exactly what that looks like. If you’re wondering by what magic the marker balls get installed on hard-to-reach power lines, it sometimes takes one helicopter and a very plucky technician. The article also notes that the benefits go beyond aviation-the markers also help geese and boats steer clear of inconspicuous cables. Otherwise, they should alternate between orange, white, and yellow to provide the highest level of visibility to approaching aircraft.Īccording to a 1983 article from United Press International, the marker balls first gained popularity in the early 1970s, when Arkansas’s then-governor Winthrop Rockefeller noticed electric wires whiz by as his aircraft started to land and decided something should be done to make them more obvious to pilots. If there are fewer than four marker balls on a given wire, they should all be “aviation orange,” the fluorescent hue you probably associate with some communication towers. They should be spaced evenly at roughly 200-feet intervals along regular wires, and with less space (30- to 50-feet) intervals on wires near runway ends. The diameter of the balls must be at least 36 inches on wires that cross canyons, lakes, and rivers, but the FAA allows 20-inch spheres on power lines fewer than 50 feet above ground level and within 1500 feet of an airport runway end. The Federal Aviation Administration regulates these marker balls and details their specifications in the Advisory Circular No. Though you might not have realized it, you usually spot marker balls near mountain passes, deep valleys, major freeway crossings, and airports-all locations where aircraft tend to fly at low altitudes, running the risk of getting tangled up in the hard-to-see cables.
Though we sort of wish they were rogue holiday decorations local governments forgot to take down, the truth is that they’re actually used for aircraft safety.Īccording to electric utility company Edison International, the balls are called visibility marker balls (or just marker balls, for short), and they help make power lines more obvious to low-flying aircraft like planes and helicopters. If you've ever driven past those colorful balls strung up along a power line, you might have wondered about what purpose they serve-a thought that usually disappears as soon as the balls have faded from your rearview mirror.