Leif Neland wrote:

George Herold formulerede spørgsmålet:
2: In incandescent traffic signals, the bulbs for yellow last longer
than
for red and green. So even after being switched on and off about a
million times, on-time is still a significant factor in life
expectancy.

However, traffic signal bulbs have a more vibration-resistant
filament
than standard incandescents.


I've been told traffic signals have resistors across the relays (or the
semiconductor equivalent), so the bulbs are never turned completely
off, eliminating the turn-on surge.

But it may be just rumours...


That technology was called 'Keep alive' which ran a low voltage to
lamps to extend their useful life. I saw it used on displays for
mission critical applications, but never on a traffic light.