They are signalling power and status.

BBC: Neanderthals used feathers as 'personal ornaments'

The firm said it continuously monitors track, signalling, overhead power supply and other equipment for ageing and degradation.

BBC: England

Network Rail has upgraded power supplies and signalling systems and lengthened 41 platforms at 12 stations on the Midland main line north of London to accommodate the new trains which are nearly 270 yards (250m) long.

BBC: Longer trains set to ease congestion on Thameslink line