Photometric testing.
Actually, the legal requirements in force in North America agree with me, and not with you. If you believe otherwise, your understanding of the applicable regulations is faulty.
DS (the legal requirements in force everywhere else in the world also agree with me, but that's beside the point).
That is not correct. 49CFR564 contains the specifications for replaceable headlamp "light sources" (bulbs). The actual Federal requirements for car lights, contained in 49CFR571.108, actually state the opposite of your faulty understanding: The design and performance characteristics of every light source are mandatory, and cannot be selectively modified to suit the whim of whoever's doing the modification. Any modification -- different power rating, different filament configuration, replacement of filaments with arcs or arcs with filaments (or arcs or filaments with LEDs, etc.) -- means it is a different light source, not legally interchangeable.
Furthermore, 49CFR564 contains the specifications only for forward illumination light sources ("bulbs"). Signalling light sources are not contained in 49CFR564. The exact legal reason behind the illegality of "LED bulbs" is a little tricky to follow: When such bulbs are installed, they spoil the compliance of lighting devices designed to use a filament bulb of one sort or another, and manufacturer-certified as compliant with FMVSS108 when using that filament bulb. So it's not the bulb itself that's illegal to sell, buy or install, it's what happens to the performance of the vehicle lighting device as a result of installing the "LED bulb".
In actual fact, "LED bulbs" do not produce anywhere near the same amount of light as a filament-type signalling bulb, nor do they produce anywhere near the same (Lambertian) distribution of light...even those clever ones with sideward-facing LED emitters in addition to the rearward-facing items. Installing "LED bulbs" in bulb-type car lamps doesn't just spoil their compliance with the applicable safety standards, it spoils their performance. The light is too dim, the illuminated area is too small, the intensity ratio between bright (brake or turn) and dim (tail or park) is improper, and the vertical and horizontal angles of visibility are much too small. All of this adds up to grossly reduced vehicle conspicuity and safety.
DS
Thanks Dan
I wondered why my city was replacing the traffic light lamps with led's. Never knew that they had a smaller field of view. And ya during the summer sun in the desert you can hardly see them unless there are hoods over the lens. Ok they probably save a dime or two in maintenance and energy.
This is a departure from the topic that was being discussed (retrofitting automotive lighting devices with "LED bulbs"). Were you wondering why they were replacing the entire traffic light instead of just screwing in an "LED bulb"?
Well, individual LED emitters give a highly directional beam (light emitted in one direction), while a filament lamp produces light in an even sphere (light emitted in all directions). But, LED traffic lights -- like LED vehicle lighting devices -- are engineered to produce the required amounts of light through the required angles of visibility.
H'm. That's an interesting complaint. Most all of the LED traffic signals I've seen in North America and Europe are considerably more conspicuous than their filament-lamp type counterparts. And, FYI, the LED traffic signals save a fortune, not a dime or two, in maintenance and energy.
DS
Not a complaint, just an observation/realization. Until I read your post I never thought about the field of view. Makes sense to keep lights "focused" into the area needed. As long as you in the area being served the led's do tend to stand out more. I will need to keep this in mind the next control panel I build that has a "whole lot of little tiny lights"
I have installed LED's in exit signs when the company had the money. Over all we have reduced the loading on the generators by ~25 kw. Also do not have to visit the exit sign again, probably in my career. Most of the retro fits are guaranteed for 10 years. Which means they will probably last a lot longer.
Around here they usually install LED retrofits in the traffic lights unless the signals don't meet current spec in some other way. The retrofits take the place of the reflector and lense, and mount in the door with the existing lense mount.
I've also seen retrofits that were a disk shaped pcb full of LED's with a screw base on a post on the back side but those are much less common.
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