In article , Josepi wrote in part:

BTW: LEDs in traffic control lights are typically replaced every two years.
The individual units continually burn out with the severe heat and current
demand on them.

I have plenty of experience where I have been able to track individual
units due to fading and/or a few LEDs being burned out and/or LEDs of a
particular spectral characteristic are obsolete for the purpose due to
lower efficiency than more modern ones. I can tell you that LED traffic
signal units have a very high rate of lasting a lot more than 2 years -
more like 5-10.

- Don Klipstein )