In article , Josepi wrote:
The traffic light people cannot afford failures. The legal implications are
too great. I am not sure if it is based on manufactures warraties,
recommendations or history but we still ocasional segments missing.

With LED experience this may also be a heat problem with retrofitting old
units and heat not being drawn away?? When you push LEDs too hard they don't
last long. This is only from a small sample area with slightly over $500K
population.

I meant being kept in service for 5-10 years. Most of Philadelphia's
red ones installed in the 1990's and using an LED chemistry since
superseded in traffic signal use are still working and in service, not
relaced just for a few LEDs being out.

Now that they are making them with power consumption as low as 7 watts
for ones 8 inches in diameter and 8 watts for the ones 12 inches in
diameter, heat is not that big a deal in traffic signals that had
incandescents of 92 or 116 watts. Such huge reduction in power
consumption occurs in part from not having 70-75% of the light blocked
by red and green filters.

If any failure is so intolerable, then why were incandescents
acceptable?

- Don Klipstein )

"Don Klipstein" wrote in message
...
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 )

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.