Interesting Pacifica feature

Its non-standard and not (strictly) legal. Its also a hellishly BAD
idea, right up there with blue-tinted bulbs and clear turn signals...
and quite often found on the same idiot-mobiles that have those features
too. Signal lights do standardized things for a very good reason... so
that no one gets killed while trying to figure out WTF a non-standard
blinking light "means".

Worst offender locally- the city bus system with their non-standard
"deceleration lamps." Is he stopping? No. Is he signalling a turn? No.
Is he actually slowing down? Not perceptibly. So we get a blinking
christmas tree of amber lights that mean NOTHING and distract from the
two small signals that really DO mean something. What are these people
smoking?

 

Worse than with a single, center-mounted lamp. Yes.

OK, so you disagree with reams of data garnered from simulations,
controlled-environment studies and quantified real-world experience,
because the data don't match your opinion which is based on nothing
but...your opinion.

Just so we know where you stand.

I'm not aware of any such study.

It's within the positional requirements of North American and
international European regulations.

You can see that CHMSL over the roof of the Chevrolet Caprice in front of
you even if you're in a Civic. What's your point?

If you're at the 8:00 position relative to the Yukon, you aren't within
the angle of visibility the CHMSL is intended to cover. This objection is
like saying you can't see the right front turn signal when you're standing
next to the driver's door.

Quite correct. The US runs the show in North America. Regulators in Canada
and, to a lesser degree, in Mexico don't like it, but that's the way it
is. By and (very) large, what the US says goes.

Pardon my apparent lack of explicitness: This refers to the many countries
outside North America that adhere to ECE regulations. So that's all of
Europe, all of Scandinavia, most of Asia, Russia, Australia, New Zealand,
South Africa and a great many more I'm not listing here.

It doesn't work this way. For seven years, CHMSLs weren't allowed in
Germany or in the middle eastern countries, amongst many others. US
vehicles shipped to those countries for sale as new had the CHMSL removed
or the lens blacked out and the bulb removed. Remember also that the CHMSL
required in North America is different from the rest-of-world one. There's
a significant amount of overlap in the design, performance and mounting
specs, so it's fairly easy to make a "World CHMSL", but it's not
automatic. Same goes for every other exterior lighting and signalling
device.

Right, because your guesses and opinions trump data...

Didn't happen like this, either. See above.

Consumer cost protection, perceived safety detriment, national
stubbornness...there are all kinds of reasons.

Remember that the European approach to automotive equipment regulation is
conceptually opposite to the North American approach in that in most
European countries, a device or function is not allowed unless it is known
to be safe, while in North America, a device or function is allowed unless
it is known to be unsafe.


DS

 

ANY reason is a good reason.

 

Douglas G. Cummins wrote:

, but slow-moving

Which can be done just as well with a rotating beacon using LEDs as can
be done with an omnidirectional beacon using a xenon strobe....

 

R.Lewis wrote:

Actually, its quite well understood, and the products have already
penetrated the market heavily. LEDs have probably grabbed more than 50%
of the commercial vehicle signal lighting market in recent years (Dan,
got a number?), and- at least in my metro area of about 1 million- 100%
of the traffic signal market.

 

Victor Roberts wrote:

Efficacy- how well does the lamp convey the intended information? It
doesn't matter if it takes the whole Comanche Peak nuclear generating
station to run the lamp, it can be very efficacious so long as it
conveys the signal well.

Efficiency- how much input power does it take to achieve efficacy?

LEDs are much more efficient and COMPARABLY efficacious to incandescent
lamps in most signalling applications. For some applications (eg.
headlamps, stadium lighting) LEDs aren't efficacious enough yet. For
others (traffic signals, turn signals, brake lamps, small hand-held
flashlights) they are.

 

Efficacy is a measure of how well a source produces visible light. It
is measured in lumens out per watt in. I don't understand how you
measure "conveys the signal well."

Efficiency for any energy conversion device, including light sources,
is simply power out divided by power in.

LEDs are much more efficacious than incandescent lamps ONLY when
compared to filtered incandescent lamps. That is, when most of the
light generated by the incandescent lamp is absorbed by a filter that
transmits only a relatively narrow band of light, such as in almost
all signaling applications. Since LEDs are naturally narrow band
sources, they do not use absorptive filters and do not suffer from the
filter loss.

When competing with white light sources, current generation LEDs have
about the same efficacy as good incandescent lamps, since in this case
the incandescent lamps are not hobbled by an absorptive filter. I
agree that for very low lumen applications LEDs may have higher
efficacy than some very low power incandescent lamps used in devices
such as hand-held flashlights, but even this is not certain. I have
seen efficacy data on flashlight bulbs that is equivalent to typical
LEDs. However, there is no question that LEDs have longer life and are
more rugged than these low power flashlight bulbs.

 

Have the (local) specifications for the traffic signals been altered to
accommodate LEDs or are they, as I understand is not uncommon, just 'under
test' ?

 

Within a small community, it may indeed have such a rigorous definition.
So might the word "snorklefroodle," but who cares? I've got two degrees
in electrical engineering, but have never been subjected to such a tight
definition of "efficacy," and I suspect that no one in any of the
newsgroups other than s.e.l. has either. In the general sense, efficacy
is simply a measure of the capability to produce a desired effect. A
signalling device that uses the entire power output of a Westinghouse
pressurized water reactor to convey the signal "stop at this
intersection" (or a bazooka to swat a mosquito) may be 100% effective,
but horribly inefficient.

Efficiency, however, has a rigorous definition of power out divided by
power in, and that applies to all audiences. Effectiveness is by no
means strictly tied to efficiency in any sort of general sense.

And since we're talking specifically about signalling (subject is
'emergency lights'), name me an incanedescent lamp that can be used to
produce red, blue, green, or amber light without filtering.

 

Yes, what's your point? If you had read the earlier post, you would
have read that I said there aren't any viable LED beacons in the market
yet. But that doesn't mean there won't be in the future. I just found
this:

http://www.911ep.com/PDF/360StarFinal.pdf

I've also seen several other prototypes from many other manufacturers.

 

You are absolutely correct. I should have said that the "efficacy of a
LIGHT SOURCE is defined as .... " Since I am answering this question
in sci.engr.lighting, I assumed, incorrectly, that this qualifier was
not necessary.

None, and that is the point of the discussion. The only way to get
narrow band emission from an incandescent source is to use absorptive
filters, which dramatically reduce the efficacy of the incandescent
lamp. Under these conditions current generation LEDs have higher
efficacy than filtered incandescent lamps, but, as I stated before,
this advantage disappears in almost all cases when comparing white
light sources because the filter is no longer used with the
incandescent lamp.

 

The point is that if your in a smaller car following a Pukon, the light is
so high
that if your tailgating it's out of your field of vision.

Of course I'm not endorsing tailgating here, but since the CHMSL is supposed
to prevent rear end collisions by morons who tailgate, putting it that high
makes it pointless to have.

And if your not tailgating but your the second car behind, well I don't know
about
where you live but here there's a lot more SUV's and trucks and minivans
than Caprices
that would entirely block the CHMSL no matter where it was placed. You
claimed one of the reasons for the thing was so that vehicles behind could
see
through the windshields of the ones in front of them.

Almost certainly any study that claims that the CHMSL is normally visible
through the windshield and backglass of interceding cars must have been
done in Europe somewhere. In the US at least half to 3/4 of vehicles on the
road you can't see squat through.

It may not be intended to cover that position. But you can see other
vehicles CHMSL's at that position. So once again why were the stylists
allowed to move it to a position that makes it less safe than the
competition?
(I know, they wanted to produce an even uglier SUV than the competition)
OK, so this example may be more one of deliberately not taking advantage
of a "safety" feature that your mandated to have, (ie: stupidity) than any
argument for or against the CHMSL. But it does illustrate the silliness of
the
regulations that they are so lax as to allow the Pukon to move the lamp
to such a dumb place - it's definitely not in the axis of the drivers field
of
vision.

cost protection on a ten cent lamp in the back of the car? (in quantities
of
ten million or whatever that the automakers buy them at) Automakers spend
more money on fancy logos that they plaster over the ass-end of the
car. OK, as for the other reasons, I guess I can't argue that people that
would believe those kinds of stupidity don't exist.

Good point, I wish the US was like this for a lot of things on vehicles.

Ted

 

Victor Roberts wrote:
....

I have not followed this entire discussion, but I won't let that
stop me from commenting that The avowed point of LED stop lights
is that it is FASTER AND therefore a more effective way of letting
the person in the rear know that they should take action. - RM

 

The city has decided that they will no longer use ANY incandescent
signal traffic signal lamps. All replacements are to be with LED arrays.
That decision is probably 9 months old, and its already nearly
impossible to find an incandescent traffic signal anymore. They were
"under test" at selected intersections 5 years ago, and that is the
basis for the wholesale conversion.

 

After 5 years the degradation will be getting significant.
How do they measure/monitor them for specification or is it a time-planned
automatic replacement.?
Are they color controlled in any way?

 

Thats a lot more detail than I know about the program. My guess is that
the city enineers buy the modules from some vendor, and they know that
they don't have to replace them nearly as often as they do
incandescents. Replacement probably is triggered more by percentage of
elements in the array not working than by any degradation of each
element's output or color.

 

[dire warnings of LED inadequacy, degradation, inefficiency,
inapplicability and assorted other such piffle]

Look, Mr. Lewis, I donno why you're so rabidly against LED traffic and
vehicle lights. They exist, they work well, and they save a lot of money
in operating and maintenance costs compared to the incandescent and strobe
devices they replace. While some of the problems you mention are indeed
real technical issues with LEDs, they are addressed adequately in the
units that are actually in service.

Virtually every locality that "tested" LED traffic signals went ahead and
installed them right across the board, not even waiting for the
incandescent ones to burn out. Yes, they really do cost *that* much less
to run and maintain.

The only real remaining issue with LED traffic signals is that they can be
excessively intense, causing glare after dark -- especially the green
ones. This is handled in European regulations that call for traffic
signals with a higher daytime and a lower nighttime intensity; I'm not
aware of any such dual-level installations in North America. As the
technology and the regulations evolve, manufacturers will probably feel
less urge to use the most intense LEDs they can (which has in the past
been done both for the "Look what we can do!" effect and probably to
ensure the devices are still compliant after several years' service).
Consider that the original red traffic signals contained 800 emitters and
the latest ones contain 2 emitters(!). The technology is a great deal more
advanced than you seem to be willing to grasp, for reasons unknown but to
you.

<sarc>
Naw. They just use any ol' colour. They turn 'em all green for St.
Patrick's day, and they're all pink in Castro and Dupont Circle. And in
the Haight-Ashbury and Eugene they've got colour-changing ones what swirl
around like a lava lamp.
</sarc>

DS
(Never thought I'd say this, but where's whatsisface Lowrie with his
Amazing Patent Pending LED Turnip Twaddler when you need him???)

 

It is unlikely that replacement is triggered by the percentage of LEDs
in the array that fail to work. Or, if this is the method used, then
it will lead to serious problems.

Unlike incandescent and discharge light sources, most LEDs will
operate virtually forever, but with a continuously decreasing amount
of light output. The old definition of "lamp life" as being the time
required for 50% of a large sample of lamps to fail is not applicable
to LEDs because of the different way in which they "fail".

The LED industry is moving toward a new definition of "life" for LEDs
that is based on the time required to decrease to 50% of their initial
light output. I believe the 50% cutoff gives an overly optimistic
result for LED life, since incandescent sources and most discharge
sources will have lost much less than 50% of their initial output by
the time they fail.

Since good lighting systems are designed on the basis of mean lumens
instead of initial lumens, using 50% loss of light as the definition
of end of life for LEDs will further reduce the mean efficacy of LEDs
when compared to existing white light sources.

 

| > Are they color controlled in any way?
|
| <sarc>
| Naw. They just use any ol' colour. They turn 'em all green for St.
| Patrick's day, and they're all pink in Castro and Dupont Circle. And in
| the Haight-Ashbury and Eugene they've got colour-changing ones what swirl
| around like a lava lamp.
| </sarc>
|

ROFL. I want one of those swirling lava lamp traffic lights for my rec room.
<g>

 

I agree.

If you look at the LED manufacturer's graph for intensity over life, for
a given LED (meaning individual LED die or commonly packaged array of
dies), it is a series of curves with each curve being for a given drive
current. Bottom line is that the intensity curve for a given end
product that contains the LED's will be very much dependent on how hard
the LED's are driven in the particular design (as percentages of their
max. allowable ratings). If there was difficulty meeting some initial
brightness spec. in the design phase (i.e., the technology was being
pushed to the edge for the particular application), there is more
likelihood that the engineer pushed it pretty hard, and degradation will
be more rapid. As the technology matures (and it has already to a great
extent), the designs can be less close to the edge, and degradation can
be easily insignificant over many years.

Similarly, one manufacturer may gain an initial competitive advantage by
driving them harder for higher initial brightness, but find that it's
competition wins out in the long term if they (the competition) use more
conservative designs (by using, say, more LED's and driving them less to
achieve the same intensity - costs more, more parts - but lasts longer
for lower overall long-term costs).

BTW (some LED trivia) - it was only within the last fifteen years that a
blue LED was commercially available - that was a holy grail of the
industry, and was quite a breakthru when it was achieved.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")