xenon "blue" lights

[wolfie]

I wonder how (or if) LED traffic lights solve this?

This issue has been discussed, and "put on an electric heater grid" looks to me to be the simplest answer. Another contributor has brought up the reason for combining taillights and brake lights/turn signals in a single bulb.

[protege]

I wondered what had happened to those. They seemed to be everywhere for about a year, but now I see them hardly ever.

The fad seems to have ended. Probably...because the people that bought high-end Audis, BMWs and other expensive rides...got tired of seeing "their" lights showing up on shitbox Honda Civics and Chevy Cadavaliers But seriously, things seem to have moved to the "white" end of the spectrum. That is, many lamps now fitted to those cars are more white, than the more-yellow lights fitted to many cars now.

Oh, and it's not just in the real world either. There was a period that model manufacturers insisted on fitting bluish LED lamps into their locomotives. They too have uh, seen the light (pun intended!), and new designs now come with slightly yellow, or even white, LEDs instead. At the time, it was felt that the bluish lamps made the models more realistic. But, from personal experience, they didn't. Real locomotive headlights have a slight yellowish tinge to them

[wolfie]

There was a period that model manufacturers insisted on fitting bluish LED lamps into their locomotives. They too have uh, seen the light (pun intended!), and new designs now come with slightly yellow, or even white, LEDs instead.

That's probably a matter of availability. Until fairly recently, the only 3mm and 5mm white LEDs (sizes model manufacturers would use) were "cool white". The LED makers were going for efficiency at the expense of colour accuracy - even now, "warm white" is slightly less efficient than "cool white".

Also, there's no such thing as a "white LED" - what's sold as that are blue LEDs with a phosphor coating (yellow under reflected light with the LED off - look at any LED flashlight and you'll see). If the coating's too thin (i.e. cutting corners to save money), you'll get an even bluer tint, since not all of the original blue will be absorbed (and re-emitted at a longer wavelength). If you look at the specs, you'll see white LEDs claiming a 10,000 hour lifetime, but red, amber, green, and blue claim 100,000 - that's because the phosphor layer "wears out", so the tint will go more to the blue end as the LED ages.