why do some power lines have balls on them

Have you ever seen those big yellow, orange, white or red balls hanging from power lines and wondered what they re used for? They re called visibility marker balls or marker balls. You ll often find them near mountain passes, in the deep valley areas, near major freeway crossings and around airports.

They weight about 17 pounds each. The marker balls are placed on power lines to make the conductor crossings visible to aircraft. Helicopters and small aircraft often fly low in mountain passes or freeways and usually fly low while approaching an airport.

When you are flying, the conductors and skyline become almost invisible against the terrain especially the skyline wires. Many of the marker balls are required by the Federal Aviation Administration (FAA), like the ones near airports.

Over the years, Southern California Edison has also identified areas that are particularly hard to see. Next time you re driving past a marker ball, remember that they re used for the safety of the flying aircraft and to protect the electrical infrastructure.
Asked by: Claire Buckley, Ireland The coloured balls on overhead electricity cables act as visual warnings for low flying aircraft.

They are most often used when cables cross major highways or deep gullies or valleys.

To aid visibility, the colours are chosen to provide the greatest possible contrast with the background terrain. Where more than one cable is strung between the pylons, the coloured balls are mounted on the highest.