You’ve probably seen those reddish-orange balls that hang like Christmas lights on power lines here and there, but have you ever stopped to wonder why they adorn some and not others? Is there a reason, or do the electrical companies in some towns just feel more festive than in others?
The helpful little orbs are called visibility marker balls (or just marker balls), and they help make power lines more obvious to low-flying planes and helicopters. The reason you don’t see them everywhere is because they’re typically used near mountain passes, deep valleys, major freeway crossings, and airports – all locations where airplanes are more common and run a greater risk of getting tangled in cables they couldn’t see in time.
Marker balls are regulated by the Federal Aviation Administration (FAA), including specifications as far as size and shake. Their diameter must be at least 36 inches on wires that cross canyons, lakes, and rivers but can be as small as 20 inches across on power lines below 50 feet above ground and within 1500 feet of the end of an airport runway.
They’re also required to be spaced evenly – 200-foot intervals on regular wires and 30-50 feet intervals near the ends of runways.
Lines that sport fewer than four balls will be “aviation orange,” but otherwise, the markers should alternate between orange, white, and yellow.
Marker balls came about in the 1970s, when then-Arkansas governor Winthrop Rockefeller noticed how close he came to power lines while landing his aircraft, and they have also come to assist boats in the same manner.
They’re installed by the power companies (sometimes by helicopter), and they allow pilots and boat captains everywhere tpo sleep a little easier.