I'm not sure the new LED lights for cars and traffic signals are a good thing

[Peter Constantinidis]

Where I live I am increasingly seeing more and more car taillights using
LEDs, primarily buses, but also recent model passenger cars.

Traffic signals are also starting to install them.

The reason I am concerned about them is because they are so dazzingly
brilliant.

On car taillights I am starting to have to avert my gaze away from the car
in front of me because I am finding the lights too bright, esp. after I
have adjusted to darkness. I have even seen a 18 wheeler that was studded
with LEDs all over and looked like a giant christmas tree. Even during the
daytime they are awfully bright, the traffic signals can be seen far off
into the distance. This means I have another use for my tinted windshield
banner, to cut glare from traffic lights in addition to the streetlights.

I thought we had laws saying that you cannot have lights on the back
brighter than a certain amount. I recently was behind a guy who either
removed his red plastic plate in front of his middle window brake light, or
replaced the bulbs with high output white bulbs. It was very uncomfortable
and I don't feel it increased road safety for either of us.

I also see a lot of people driving with ultra brilliant fog lamps and what
appears to be high beams.

Is there anyone out there in legislative land paying attention to these
issues? Too much brightness in my opinion is a road safety issue as is too
little.

 

[Douglas G. Cummins]

Where I live I am increasingly seeing more and more car taillights using
LEDs, primarily buses, but also recent model passenger cars.

Traffic signals are also starting to install them.

The reason I am concerned about them is because they are so dazzingly
brilliant.

On car taillights I am starting to have to avert my gaze away from the car
in front of me because I am finding the lights too bright, esp. after I
have adjusted to darkness. I have even seen a 18 wheeler that was studded
with LEDs all over and looked like a giant christmas tree. Even during the
daytime they are awfully bright, the traffic signals can be seen far off
into the distance. This means I have another use for my tinted windshield
banner, to cut glare from traffic lights in addition to the streetlights.

I thought we had laws saying that you cannot have lights on the back
brighter than a certain amount. I recently was behind a guy who either
removed his red plastic plate in front of his middle window brake light, or
replaced the bulbs with high output white bulbs. It was very uncomfortable
and I don't feel it increased road safety for either of us.

I also see a lot of people driving with ultra brilliant fog lamps and what
appears to be high beams.

Is there anyone out there in legislative land paying attention to these
issues? Too much brightness in my opinion is a road safety issue as is too
little.

Every regulatory body (ECE, DOT, etc) has requirements on how "bright "
a lamp - any lamp - can be no matter what the light source is. All
LED-based lamps are supposed to meet the same requirements - both
minimum and maximum - as incandescent-based lamps. You can't say that
LEDs are brighter - that's like saying red cars are faster. It's all a
matter of design.

If you feel people are abusing the system, contact your local
authorities. If you think the traffic signals are too bright - complain
to the city manager. If somebody added twenty marker lamps to his
vehicle and you think it's too bright - call the police or highway
patrol, they can site motorists for creating unsafe driving conditions.

 

[Daniel Stern Lighting]

Where I live I am increasingly seeing more and more car taillights using
LEDs, primarily buses, but also recent model passenger cars.
Traffic signals are also starting to install them.

Yep. The adoption of LED traffic signals, in particular, has been swift.
They pay for themselves *very* quickly in *hugely* reduced energy
consumption and *hugely* lengthened service intervals.

The reason I am concerned about them is because they are so dazzingly
brilliant.

Some of them certainly can be, particularly a great many green traffic
signals. The problem is that the standards for traffic signals were
written when there was only one kind of light source -- an incandescent
bulb. There is some feeling that the existing standard may not properly
assess the output of LED traffic signals, and this is being investigated.
In Europe, they use variable-intensity LED traffic signals that are dimmer
at night than during the day.

On car taillights I am starting to have to avert my gaze away from the
car in front of me because I am finding the lights too bright, esp.
after I have adjusted to darkness.

Again, in Europe there are standards in place for variable-intensity
vehicle signals that produce amounts of light appropriate to the level of
dark adaptation of observers, though I'm not specifically aware of any
vehicles that actually do so, yet.

The US standards allow much more intense brake and rear indicator lights
than are permitted in most of the rest of the world; the glare problem is
not limited to LED units. The rear indicators of a '96-'97 Taurus sedan,
for instance, and the brake lights of a current US-model VW Passat, are
glaring and more intense than is necessary to do the job adequately.

That's not to say that the European standard is, on the whole, better. Its
minimum-intensity levels are a bit on the weak side, and its maximum brake
lamp intensity is lower than it should be. It'd be best to have one
worldwide standard with sensible minimum *and* maximum values. Don't hold
your breath.

I have even seen a 18 wheeler that was studded with LEDs all over and
looked like a giant christmas tree.

Well, that's a result of laws that say once the standards are met with the
minimum necessary lighting equipment, you're free to add whatever other
equipment you want, as long as the optional equipment complies with
overspanning rules (such as light color) and does not interfere with the
function of mandatory equipment. Some of the truckers like to have four
and five and ten brake lamps per side, three hundred sidemarker lamps,
etc.

I thought we had laws saying that you cannot have lights on the back
brighter than a certain amount.

Well...no. We don't. There is a Federal standard for *each individual*
lamp, and one for lamps containing multiple bulbs. State standards
generally say little or nothing relevant on the matter, so all the extra
lights are usually legal.

I recently was behind a guy who either removed his red plastic plate in
front of his middle window brake light, or replaced the bulbs with high
output white bulbs. It was very uncomfortable and I don't feel it
increased road safety for either of us.

Well, that's a noncompliance with the Federal standard and almost
certainly with the state standard -- white light shining rearwards is
legal only in the case of reversing lamps.

I also see a lot of people driving with ultra brilliant fog lamps and
what appears to be high beams.

This is (slowly) being addressed by the Feds and (even more slowly) by the
states. There is a National Highway Traffic Safety Administration docket
(Number 8885) open for glare issues, focusing primarily on glare from
forward lighting (headlamps, fog lamps, etc.). You can access all of the
responses, or submit your own, at http://dms.dot.gov . If you wish, you
may read my response here:
http://www.pergolesi.demon.co.uk/dastern/

DS

 

[Hi Ho Silver]

$On Tue, 12 Aug 2003, Peter Constantinidis wrote:
$> On car taillights I am starting to have to avert my gaze away from the
$> car in front of me because I am finding the lights too bright, esp.
$> after I have adjusted to darkness.
$
$Again, in Europe there are standards in place for variable-intensity
$vehicle signals that produce amounts of light appropriate to the level of
$dark adaptation of observers, though I'm not specifically aware of any
$vehicles that actually do so, yet.

I haven't found them dangerously bright, but I've noticed that
truck and bus taillights that use LEDs have a different problem: they
appear to be a number of very bright point sources. Traditional
taillights tend to use reflectors or diffusers or whatever else to
take the light from one bulb (whose filament is larger than an individual
LED anyway) and spread it at least somewhat over the lamp area.
For some reason, the LED ones don't seem to do this; each LED is clearly
visible, and the areas between them don't seem to get a lot of light.
So while the overall light output may be comparable to that of
a conventional bulb (or it may not - I really have no idea), the
brightest parts are _way_ brighter than with conventional bulb
assemblies.

Is it just me that thinks this is an odd way to set things up?

 

[Helmet Head]

I haven't found them dangerously bright, but I've noticed that
truck and bus taillights that use LEDs have a different problem: they
appear to be a number of very bright point sources. Traditional
taillights tend to use reflectors or diffusers or whatever else to
take the light from one bulb (whose filament is larger than an individual
LED anyway) and spread it at least somewhat over the lamp area.
For some reason, the LED ones don't seem to do this; each LED is clearly
visible, and the areas between them don't seem to get a lot of light.
So while the overall light output may be comparable to that of
a conventional bulb (or it may not - I really have no idea), the
brightest parts are _way_ brighter than with conventional bulb
assemblies.

Is it just me that thinks this is an odd way to set things up?

As bright as some LEDs are, one might get a more uniform pattern
by aiming them at the (redesigned) reflector, instead of at the
lens. [?]

 

[Daniel Stern Lighting]

As bright as some LEDs are, one might get a more uniform pattern
by aiming them at the (redesigned) reflector, instead of at the
lens. [?]

This would introduce more problems than it would solve. Additional
complexity, an additional level of optical design (and expense, and
inefficiency), additional component depth. There's no need for any of
this; there exist many LED vehicle signal devices that do exhibit this
"many bright point sources" effect, but there also exist many that do not.
The Cadillac DeVille, Mercedes S-Klasse and BMW E46 are three car models
that from most angles you have to scratch your head and ask "Are those
LEDs, or...?". The universal-fitment truck/bus units also vary widely. You
can see individual point sources in some of them, but not in others,
depending upon the design.

With the rapidly increasing efficiency of LED emitters, the number of
individual emitters per assembly necessary to meet the photometric and
geometric requirements is dropping. With very high *or* very low emitter
counts in an assembly, the "individual point source" appearance is
minimized. With very high emitter counts (40, 50, 60, etc. -- Petersen
Mfg. still makes some like this, and a lot of FedEx trucks use them in the
4" round format), the emitters are packed so closely together that you can
only see them clearly as individual point sources if you're very close to
them. With very low emitter counts (1, 2, 5) the optics required to spread
the light from so few emitters through such wide angles as are required of
most signalling functions are such that the emitter heads blend into the
illuminated optics.

The technology is still young, and its maturation is being extended by the
fact that not only the light sources but the optics are evolving, and the
regulations applied to devices so equipped, too. Give it some time.

DS

 

[Daniel Stern Lighting]

Actually, there isn't really legislation on brightness for signal lamps.
There is legislation for intensity which is a measure of flux (power)
emitted into a solid angle. Intensity doesn't deal with the source
characterstics (ie size/area). When someone talks of something being
too bright, they are usually referring to what is known as the
luminance. The luminance is related to the power emitted per unit area.
This is what one sees when they look directly at a lamp and the
brightness will be affected by the size of the lamp. Intensity would be
more related to what one might see on a wall a long distance from a
lamp.

Marty, you're exactly right. I've long felt that luminance standards for
signal lamps would make a tremendous amount more sense than intensity
standards. Intensity serves as a passable proxy for luminance in most
reasonably conventional cases, but tends to break down in what might be
called "extreme" cases (very large or very small device projected area,
non-bulb light sources, traditional bulbs with nontraditional
optical techniques, etc.).

It's interesting to note that while the European intensity maximum for
e.g. brake lamps looks alarmingly low at just 160cd, one does not often
get the impression of inadequate brake lamps while driving in a country
governed by European (ECE) lighting regulations. This apparent
contradiction becomes easier to swallow when we observe that most
ECE-compliant brake lamps are on the small side compared to their US (SAE)
counterparts, but use very similar light sources. This is probably a
result of ECE regulations requiring a greater number of separate rear
signalling functions (amber turn signal, red tail/red brake, red rear fog,
white reverse, red retroreflex, minimum separate total of five, compared
to US/SAE requirement for red turn signal/red tail/red brake, red
retroreflex, white reverse, minimum separate total of three). As a
result, the luminance of a smaller ECE brake lamp is often greater than
that of a larger SAE brake lamp, and so both are adequate. With the
increasing prevalence of nontraditional light sources and optical
techniques, it seems to me that luminance standards would make a very good
addition to worldwide technical standards, and would almost certainly
greatly facilitate ongoing regulatory harmonization.

It does not make a lot of sense to use a measurement of how well you can
see *by* a light source (intensity) on a device the critical function of
which is how well you can *see the light source* itself.

By the same token, luminance standards for forward lighting components
(headlamps, fog lamps) would probably go a long way towards addressing the
glare problem.

DS

 

[Victor Roberts]

With the rapidly increasing efficiency of LED emitters, the number of
individual emitters per assembly necessary to meet the photometric and
geometric requirements is dropping.

Did you mean to say "the rapidly increasing output per emitter?" I do
not believe there has been a rapid increase in the efficiency of LED
emitters but there certainly has been a rapid increase in the amount
of light per package (through not even per junction.)

 

[Daniel Stern Lighting]

So I can't add a Q-Beam with a red lens to substitute for my CHMSL when
tailgaters are problematic, but I could put a dozen of them back there
and call them rear fog lights?

Post when you get done in traffic court and let us know how it worked
out.

DS