The Natural Philosopher wrote:
snip
LEDS die at around 100C. The reason they are used increasingly in
traffic lights is energy efficiency.

However, this is not the case for white LEDs.
For traffic lights, it's true, for a couple of reasons.

Firstly, most of the light in a normal light is absorbed by a filter,
and secondly, the bulbs are very inefficient as they are run at a low
output to increase time between failures.

LEDs produce light at one wavelength only, so need no filters.
And the way they are used in traffic lights, where there may be hundreds
per light means that they fail gradually.