> -----Original Message-----
> From: piclist-bounces@mit.edu On Behalf Of William "Chops" Westfield
> Sent: Wednesday, July 16, 2008 4:33 PM
>
> A fair number of the LED traffic lights around here have developed
> blotches of dead LEDs.  Especially the white LEDs used for "Walk"
> signals, but also even RED lights.  It's sorta sad; I bet someone in
> the local DoT is unhappy that the believed the "saves replacement
> costs" spiel..
>
> BillW

I saw this happening soon after the LED lamps were introduced in SE
Worchester County MA back about five years ago. Within a year a number of
the lamps had been replaced and since then many have been replaced with the
old incandescent type. A new traffic light was added on my commute a month
ago and that town put up incandescent instead of LED, I'm guessing that town
has given up on LED lights.

>From a drivers perspective I'd like them to put them all back to
incandescent because the LED units with multiple dead LEDs are very
difficult to see in bright sunshine. I suspect the decreased light output
when hot contributes to my difficulty in seeing some of them on hot commutes
home. The town's around here seem to wait until they have more than 66% dead
LEDs before they replace them.

My guess as to why they are such a problem up here is that they failed to
take into account the over 55 degC ambient temperatures inside a traffic
light on a hot southern New England summer day. Add in all the heat from the
LEDs and it wouldn't surprise me if on some days it's well over 80 degC in
the light fixture.

Paul Hutch


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