Too-Bright Headlights & Fog-Lamp Questions

SubLGT

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....good quality research on the subject (by UMTRI, a very reliable group of scientists in this field) concludes that safety would be improved -- meaning fewer crashes, less injury, fewer fatalities, less property damage -- if everyone used high beam after dark, even in traffic. The researchers acknowledge, however, that this would be very uncomfortable and so would not be accepted in practice....

High beams always on? Sounds like a recipe for increasing nighttime road rage incidents, with resulting deaths and injuries.
 

pungo

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This is the key, right here. What many people don't understand (or don't like to hear) is that we are not dealing with a 1:1 safety issue here where a unit of extra seeing light and a unit of extra glare light cancel each other out, safetywise. In fact, the safety benefit of additional seeing light is massively bigger than the safety detriment of additional glare. So much so that good quality research on the subject (by UMTRI, a very reliable group of scientists in this field) concludes that safety would be improved -- meaning fewer crashes, less injury, fewer fatalities, less property damage -- if everyone used high beam after dark, even in traffic. The researchers acknowledge, however, that this would be very uncomfortable and so would not be accepted in practice.
Maybe I just don't get it, but I can't understand how it would be safer if everyone drove around with their high beams on? On some of the narrow back country roads I drive, sometime an idiot will be coming toward me with their high beams on in an SUV and even though I flash my high beams a few times and they don't turn them off. A few times, even though I'm looking toward the shoulder, I've had to come to a craw since I can barely see the edge of the road. How is that safer?
 

SubLGT

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Apparently, driving with your high beams always on is popular in China.

https://www.bbc.com/news/blogs-news-from-elsewhere-37847056

Police in southern China are punishing drivers who dazzle other road users with full-beam headlights by making them stare into the lights for a minute, it's reported.

The force faced criticism for a similar initiative in 2014, but nonetheless decided to start it up again on Tuesday. This time around, the reaction has been largely positive.

Shenzhen Traffic Police posted photos of the campaign in action on their official Weibo account. "Tonight we are carrying out punishments using a high beam," the post reads. It's racked up 87,000 likes and been shared 93,000 times. The photos show people sitting directly in front of a car with its headlights on.
 

-Virgil-

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Given the influence of headlamp aim on measures of visibility and glare (Akashi et al., 2008),and the frequency of mis-aim found on vehicles, more consistent vertical aim of headlamps would provide more consistent light levels toward oncoming drivers' eyes, and reduced instances where light levels are high. Periodic adjustment of headlamp aim or automatic adjustment systems could then be helpful countermeasures against glare.
Yes, we need both of those -- periodic headlamp aim adjustment and automatic adjustment systems. This isn't a breakthrough finding or anything; read the link in post #10 of this thread.

low beam headlamp beam patterns are, if not perfect, then close to optimal
This is a good example of where contextual awareness and knowledge are required to correctly read and understand scientific writing. If this is read the same way you'd read a newspaper, it looks like it's saying low beams are pretty close to ideally suited to their task. That is not what it means. It means the writer's interpretation of the data they're working with is that U.S.-specification low beams strike the right balance between seeing and glare (which is the definitional intent of a low beam). This is not a new or groundbreaking thing; that has been the U.S. position for as many years as the European position has been that the European-specification low beams strike the right balance. The U.S. position is backed by a great deal of science; the European position is backed more by philosophical stance. As far as our discussion here on this board goes, it doesn't really move the ball any -- it's exactly where we were at post #13 of this thread. :)

Even though higher intensities from such headlamp patterns are probably necessary to ensure detection distances sufficient to respond to hazards at many driving speeds, drivers' intolerance for the discomfort glare from such intensities probably limits the feasibility of increasing low-beam headlamp intensity significantly. Many lines of evidence suggest that increasing the intensity of a headlamp will improve visibility for a driver and simultaneously worsen glare for other drivers.
Post #9 of this thread.

Adaptive headlamp systems such as the SAFS prototype evaluated through the present research program (Bullough et al., 2008) provide a possible work-around regarding the inherent conflict between visibility and glare by reducing luminous intensity only when and where other drivers are located and maintaining higher intensities for good visibility in the remaining parts of the visual scene.
Post #8 of this thread.

Thirty-six percent of the [new-vehicle sample's] VOR vehicles and 22 percent of the VOL vehicles had at least one headlamp mis-aimed by more than 0.76° and 62 percent [of the in-use sample] had at least one headlamp mis-aimed
Also not new or groundbreaking...yes (still, again, still, again) we don't care about headlight aim in North America, and while today's headlamps are easier to aim, they are also more sensitive to misaim. The two go hand-in-hand.

Toyota has apparently asked for clarification on ADB systems
The Toyota petition, back in 2015 or so, floated the idea that ADB could be considered legal within the existing text of FMVSS 108. That idea didn't find favor with NHTSA.

However, given the glacial speed of US headlamp regulations, I wouldn't hold your breath.
That's pretty much the long and short of it. Even Canada, where the vehicle standards and regulations are generally kept in close alignment with the US rules, got tired of waiting and permitted ADB. NHTSA's proposal for an ADB specification was a mess, essentially saying automakers could put ADB systems on their cars as long as the systems meet all existing high and low beam requirements and limits, which, in effect, means no ability to do what ADB systems are designed to do. NHTSA also proposed a completely unworkable test regime for ADB systems. Nobody seems to know why their proposal was such a freakshow; nobody wanted this. It's not like NHTSA had competing asks and they had to pick and choose or split the difference or compromise, etc. Pretty much everyone (car industry, lighting industry, safety researchers and academics...) is in surprisingly uniform consensus about what an ADB system should do and how it should work...except for NHTSA.

Yes, it is, for getting a pretty good background handle on the divergencies between US and "everywhere else" practice, though its publication date means everything in the last 23 years is absent.
 

-Virgil-

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Virgil, Can you point to this study? How recent is it?

It's not a single study, it's a pretty large amount of research over many years, by a pretty good list of highly capable, very reputable researchers. Yes, I could point to many of the individual papers and studies, but I have to say your post here doesn't make me want to do so. In fact, it makes me want to specifically not go get the references and post them here, and I'll let your words do most of the work in explaining why:

It seems to me that it is an older study
Did the researchers take into consideration that many the fatalities, that occur at night, are related to alcohol consumption?
It seems to me that the study you refer to is flawed.

You literally have no idea what you're talking about -- you guessed/assumed it's a single study, you guessed/assumed it's old and therefore obsolete and invalid, you threw alcohol in there because you guessed/assumed it's relevant to this discussion and you guessed/assumed the researchers must have not factored that in, and then you "concluded", based on your pile of guesses, that "the" study is flawed, and claimed victory...all without having read a single bit of the large amount of research. You seem to believe guesses and assumptions and opinions are just as valid as scientific research, but that is not the case.

If you were really curious, if you really wanted to learn and understand, you wouldn't have made this attempt to debunk from a position of pure ignorance, you would have asked thoughtful questions. Instead you demonstrated that you aren't interested in getting informed or understanding the science -- you "know" what you (think you) know, you "understand" what you (think you) understand, you have your (baseless) opinions and guesses and assumptions and what you (think you) understand of what you (think you) remember from fifty years ago, you have your misinformed, unrealistic prescriptions for how to make everything better, and by gummit, you're not about to let any stupid old study change your mind. Now, why on earth would anyone else want to do any homework or footwork for you? You have the same access to the UMTRI and RPI-LRC research libraries as everybody else, including me. When I first started accessing those resources I had to figure out how to search effectively, just like everyone else. When I find materials relevant to whatever topic I'm looking into, I have to use their bibliographies to follow the research thread and find the referenced prior research, just like everyone else.

You see...

This professorial affectation is really the cherry on top. Protip: when you're in a forum or a room populated with subject matter experts, and you start throwing around uninformed opinions and guesses and assumptions, they will be detected as such immediately -- even if you put "You see..." before them.

20 years ago, high beams may be uncomfortable when aimed into the face of oncoming traffic, but they would not necessarily be blinding. Today's lights are absolutely blinding.

This is so completely wrong, from start to finish, that it's almost entertaining.

There are another couple of spots on the way home, that are hilly, and the road curves. In these sections, the road is very dark, and my eyes are a little dark adjusted.

Yet another incorrect guess-assumption-opinion.

Often, suddenly as I approach this curve, an oncoming vehicle comes up the rise, with it's beam in my face, such, that I have to look away, and judge, that I am staying in my lane, by looking to the right hand side of my lane, for where the asphalt meets the dirt. Sometimes, the light is so blinding, that I have to hit my brakes, and am afraid, that I might be rear-ended, because the driver behind me, may also be blinded, and not see my brake lights.

You think you know what you can and can't see. You think you know when you're blinded. In fact, you know neither. This is not specific to you in particular; it applies to all human beings: we mistakenly think we know how well we can see. It's an unfortunate quirk of how our visual systems and our minds work.

I often have a vehicle behind me on the interstate, that is literally 1/4 mile away, and its headlights, lights the interior of my cab sufficiently, that I can read a gas station receipt. I can not believe, that much light, and with that much intensity, is needed to increase safety.

Reality exists as it exists regardless of what anyone thinks they can't believe. Beliefs don't have a legitimate place in this discussion.

Back in the seventies, I took a driver's safety test that warned driver's: Do Not Over-drive Your Headlights. In other words, do not driver faster than you would be able to stop, within the distance, that you can safely see with your headlights.

Fine advice -- and yet, virtually every driver outdrives their low beams on a routine basis. Telling them to stop is pointless; that's not going to happen. We have to deal with the world as it is, not as we wish it were or think it should be.

They also pointed to using low beams or fog lights, and NOT high beams, when driving in fog, AND that people have a tendency to drive faster in fog, than they should, because (they proposed) that when in fog, people lose some of their sense of speed because they can't see very far into the periphery

So here we have a presentation of what you think you remember from over four decades ago, including what you think you recall of somebody else's speculation.

All this to say... people need to be cognizant to their surroundings, and not excessively speed just because they can.

People outdrive their low beams. The only way to stop it would be to rigidly enforce a 35-mph (dry) 30-mph (rain/snow) 15-mph (fog, heavy rain, heavy snow) speed limit. That's not going to happen, and so the solution will have to be technological. For the time being, that largely means lighting.


does it suggest that I should increase the output of my headlights

Too vague a question to answer usefully, but I think you were probably asking rhetorically.

and drive with my high beams on?

That would be illegal. Nobody has proposed that everyone should drive with their high beams on. The science of the matter is that if everyone drove with high beams, there would probably be fewer crashes and pedestrian-hits, but there are many, many steps between that and a recommendation that everyone should drive with high beams. Even if you asked this question disingenuously, I can't entirely blame you for it; most people have no training in how to read and understand scientific writing, and one of the clickbait industry's tactics is to put complex, narrow scientific findings under simplistic, general headlines.

Does it mean that I would no longer be blinded if doing so?

Again with the disingenuous rhetorical question -- this time with a premise that's faulty because it's based on one of your beliefs that isn't based in reality, but rather in what you think you perceive.

Driving blind can not be a good thing.

Nobody has suggested otherwise.
 
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-Virgil-

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Maybe I just don't get it, but I can't understand how it would be safer if everyone drove around with their high beams on

There would likely be far fewer pedestrian-hits -- pedestrian-hits are the biggest group of traffic-related deaths, and most of them occur after dark, mostly because they were not adequately lit by the low beams. This does not mean everything would be better if everyone drove with high beams. It wouldn't solve every problem, it would create some new problems (the obvious one being a lot more discomfort), and there would probably be an increase in some other kind of bad event, perhaps such as run-off-the-road incidents. However, the net effect would probably be positive; there would have to be a HUGE increase in the number of run-off-roads to come close to the number of pedestrian-hits, and the percentage of run-off-roads that is fatal or severely injurious is much lower than that percentage of pedestrian-hits, so in all likelihood overall safety would be improved.

"Unintended consequences" is usually assumed to mean bad ones, but there can be good ones, too. For example, right now we know relatively little about the cumulative effect of prolonged and repeated glare on driver performance. That doesn't mean we know little, just that we know less about it than we do about immediate or shorter-term repeated or extended glare. If everyone started driving around with high beams, we would probably learn a lot about the effect on driver performance of long-term extended/repeated glare.

All of this is academic now; ADB effectively gives high-beam seeing with low-beam glare (given appropriately-written regulations and appropriate attention to headlamp aim), thus finally resolving the seeing/glare conflict that has existed in headlighting for about a hundred years.


sometime an idiot will be coming toward me with their high beams on in an SUV and even though I flash my high beams a few times and they don't turn them off. A few times, even though I'm looking toward the shoulder, I've had to come to a craw since I can barely see the edge of the road. How is that safer?

I'm not trying to be a smartass, but you slowed down, didn't you...!

One tragic effect of the present state of education, politics, and news media in the United States is that many people think all opinions are equally valid, few people are equipped to sort facts from opinions internally or externally, few people are trained in basic scientific thinking and so tend to be more comfortable with what they consider "common sense", and many people think "science" is just a word for some person's or group's self-interested opinions.

If the high intensity portion of the beam pattern (glare) can intersect the oncoming driver eyes, why is that not a safety hazard for the oncoming driver since they can be partially blinded until the vehicle passes?

The short answer is we're not blinded (partially or completely), we're made uncomfortable. It feels like "HELP I'M BLIND O MY GOD I CAN'T SEE GET THAT LIGHT OUT OF MY EYES", but that's not the actual reality of the situation. It cannot be stated often enough: there is often a large disconnect between how safe we are and how safe we feel.
 
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Poppy

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Virgil,
Thank you for your response.
I apologize for my lack of clarity in my comments, those that led you to believe that I was disingenuous. I did not intend dis-ingenuity, but rather would like to learn from you, in that you have an obvious (to me) greater depth of knowledge of the subject at hand, than I.

I drive a 2008 Mercury Grand Marquis with halogen lamps. My daughter has a Mazda CX5 with lights that are MUCH brighter than mine. Her seat is higher than mine. In my car the glare is terrible. In her car, bad, but not so bad. I have electric seats and raised my seat to the max, and that actually made an improvement, but not enough. So my question from a scientific point of view is this: if my headlights were brighter, would I perceive less glare?

Thank you for the links you posted above, I'll look through them and get back to you.
 
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-Virgil-

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I apologize for my lack of clarity in my comments, those that led you to believe that I was disingenuous. I did not intend dis-ingenuity

Apology accepted, and I in turn apologize if I reacted too harshly. When someone comes up with a tone of voice indicator system for on-screen words, they'll make a billion dollars (and they'll deserve it).

I drive a 2008 Mercury Grand Marquis with halogen lamps. My daughter has a Mazda CX5 with lights that are MUCH brighter than mine.

OK, so the questions at hand sound more like "Hey, how come her lights are so much brighter? How can I make mine better?". Is that along the lines of what you want to know?

my question from a scientific point of view is this: if my headlights were brighter, would I perceive less glare?

Yes, though we have to be careful what we mean by "brighter headlights" -- if it means more light and longer/wider seeing because we've done appropriate upgrades that preserve or improve the beam focus, then good/yes. If it means we've hacked the lights in one of a bunch of ways ("LED bulbs", "HID kits", remove the bulb shield, misaim the lamps, etc) then bad/no. With that proviso out of the way: there wouldn't be less glare, there'd be the same amount, but it would feel less debilitating because your own lights would be doing a better job for you. If you think about this for a few minutes, it might occur to you that this is consistent with the finding that if everyone used their high beams all the time, everyone would see better. We're talking about the same thing, just within different limits. The underlying principle is the exact same: the safety benefit from extra seeing light is greater than the safety drawback of extra glare light. Sounds simple, but it's not; there are many interconnected and seemingly contradictory effects at work. For example: it takes a lot more light to increase seeing ability than it does to increase glare. Another example: the placement of light within the beam most likely to provoke favorable opinions of a set of headlamps is least helpful to safety performance/actually helping the driver see. The subject really is very, very complex. For the set of questions you're asking, probably the best single-source document is SAE J2829, which goes into very well-written detail about how the tradeoffs work between seeing and glare, how seeing light increases interact with glare increases, glare characteristics of other cars' lights versus seeing light characteristics of your car's lights, etc. It's an expensive document, but while I haven't looked for this one specifically, it seems almost anything can be found if you look around/ask around on the internet these days.

An '08 Grand Marquis's headlamps can be upgraded pretty significantly. Suggest you talk to Daniel Stern (search Daniel Stern Lighting and you'll find his site)
 

Poppy

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Apology accepted, and I in turn apologize if I reacted too harshly. When someone comes up with a tone of voice indicator system for on-screen words, they'll make a billion dollars (and they'll deserve it).

:) ok we're good.
OK, so the questions at hand sound more like "Hey, how come her lights are so much brighter? How can I make mine better?". Is that along the lines of what you want to know?

No. I wanted to know if the additional brightness would make the perception of glare less. As sunlight during the day does when someone drives with their headlights on. During the day the glare is much less perceived as a hazard.
Yes, though we have to be careful what we mean by "brighter headlights" -- if it means more light and longer/wider seeing because we've done appropriate upgrades that preserve or improve the beam focus, then good/yes. If it means we've hacked the lights in one of a bunch of ways ("LED bulbs", "HID kits", remove the bulb shield, misaim the lamps, etc) then bad/no. With that proviso out of the way: there wouldn't be less glare, there'd be the same amount, but it would feel less debilitating because your own lights would be doing a better job for you.

THANK YOU that answers my question above.

If you think about this for a few minutes, it might occur to you that this is consistent with the finding that if everyone used their high beams all the time, everyone would see better. We're talking about the same thing, just within different limits. The underlying principle is the exact same: the safety benefit from extra seeing light is greater than the safety drawback of extra glare light. Sounds simple, but it's not; there are many interconnected and seemingly contradictory effects at work. For example: it takes a lot more light to increase seeing ability than it does to increase glare. Another example: the placement of light within the beam most likely to provoke favorable opinions of a set of headlamps is least helpful to safety performance/actually helping the driver see.

This is counter intuitive. Primarily because it is too vague without a beam profile. Example: a laser can create devastating glare, actual blindness, but not provide any usable seeing ability for the driver.

The subject really is very, very complex. For the set of questions you're asking, probably the best single-source document is SAE J2829, which goes into very well-written detail about how the tradeoffs work between seeing and glare, how seeing light increases interact with glare increases, glare characteristics of other cars' lights versus seeing light characteristics of your car's lights, etc. It's an expensive document, but while I haven't looked for this one specifically, it seems almost anything can be found if you look around/ask around on the internet these days.

An '08 Grand Marquis's headlamps can be upgraded pretty significantly. Suggest you talk to Daniel Stern (search Daniel Stern Lighting and you'll find his site)

[/QUOTE]

Thanks so much.
I found his site and will drop him a note.
Poppy
 
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-Virgil-

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If you think about this for a few minutes, it might occur to you that this is consistent with the finding that if everyone used their high beams all the time, everyone would see better. We're talking about the same thing, just within different limits. The underlying principle is the exact same: the safety benefit from extra seeing light is greater than the safety drawback of extra glare light.
This is counter intuitive. Primarily because it is too vague without a beam profile. Example: a laser can create devastating glare, actual blindness, but not provide any usable seeing ability for the driver.

It is counterintuitive, but it's not too vague; we don't need to account for things like lasers because we are speaking only about headlight beams.
 

pungo

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Maybe I just don't get it, but I can't understand how it would be safer if everyone drove around with their high beams on? On some of the narrow back country roads I drive, sometime an idiot will be coming toward me with their high beams on in an SUV and even though I flash my high beams a few times and they don't turn them off. A few times, even though I'm looking toward the shoulder, I've had to come to a craw since I can barely see the edge of the road. How is that safer?
I'm not trying to be a smartass, but you slowed down, didn't you...!
So people should keep their high beams on all the time when on dark country roads so oncoming vehicles can barely see the road which causes them to slow to a craw? Sorry, I guess I just can't understand how this is safe, but I'll read more of your posts in an attempt to get handle on your logic to better educate myself on automotive lighting.
 

-Virgil-

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So people should keep their high beams on all the time when on dark country roads so oncoming vehicles can barely see the road which causes them to slow to a craw?

I didn't say that, and neither did anyone else.
 

jeffsf

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From what I understand, the net impact of accidents would likely be lower if drivers always drove with high beams on.

(Edit: As suggested to me, clarifying that rate and overall impact are different is important. For example, a broken mirror and a broken leg, or a dead tire and a dead pedestrian have dramatically different impacts.)

If you do a quick check of how far a properly aimed low-beam illuminates the road, you'd find it much less than the distance traveled while recognizing a hazard and making a braking decision and the stopping distance at speeds much over 60 kph / 35 mph. Now consider that you probably need more than a hair's width above the road illuminated to recognize that hazard. Even to get 30 cm / a foot above the ground with headlamps at 60 cm / 24" above the road, you've halved the distance, and one measure of the "safe" speed drops to around 40 kph / 25 mph (in line with many US urban speed limits that I'm aware of).

If that isn't enough to convince you of the inadequacy of low-beam headlamps at much more than a crawl, consider a pedestrian crossing the street from the left. Can you really, safely detect them only illuminated up to just above the ankles, wearing dark jeans and black, canvas shoes? Even if you illuminate them up to headlamp level, you're probably still below well the bulk of their body.

In many of those situations, high-beam illumination has a great potential to allow detection, reaction, and stopping at the speeds that many presently drive with only low beams.

Some of the counterintuitivity may come from the brain getting in the way of visual reality. There is a significant difference between "blinded" and losing the ability to properly recognize road markings and have rapid and accurate recognition of hazards. While it may be bothersome, while your brain may interpret the visual stimulus as "painful", your ability to "see" important details is likely less impeded that you believe. Perhaps think of it like when you hear a loud shriek. You're not "deafened" though you might sense pain from the momentary intensity. Most of the sensory system is keyed around sharp changes, to "sound the warning" when something different happens. Even down to the neural level, the eye's response very non-linear, spatially and otherwise, helping survival-related things like edge detection and object appearance ("uh oh, that might be a predator coming my way").


NB: The net accident rate and impact is something that the behavior of a large group of drivers' behavior drives.

Scientific studies often explore hypotheses. Study results are, themselves, not recommendations.


Your expected accident rate and impact is something that you control. As mentioned multiple times in this thread, there are things you can do to reduce these other than driving with high beams on all the time.
 
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-Virgil-

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In many of those situations, high-beam illumination has a great potential to allow detection, reaction, and stopping at the speeds that many presently drive with only low beams.

Exactly right.

Some of the counterintuitivity may come from the brain getting in the way of visual reality. There is a significant difference between "blinded" and losing the ability to properly recognize road markings and have rapid and accurate recognition of hazards. While it may be bothersome, while your brain may interpret the visual stimulus as "painful", your ability to "see" important details is likely less impeded that you believe.

Exactly right.

Scientific studies often explore hypotheses. Study results are, themselves, not recommendations.

Exactly right.
 

Poppy

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This is the key, right here. What many people don't understand (or don't like to hear) is that we are not dealing with a 1:1 safety issue here where a unit of extra seeing light and a unit of extra glare light cancel each other out, safetywise. In fact, the safety benefit of additional seeing light is massively bigger than the safety detriment of additional glare. So much so that good quality research on the subject (by UMTRI, a very reliable group of scientists in this field) concludes that safety would be improved --
I searched UMTRI and found a limited number of articles using headlight and using glare as search terms. They were old, and their references were older yet. Many from the 1970's and older.
http://www.umtri.umich.edu/search-results?search_api_views_fulltext=headlight

If I am interpreting this study correctly, there is a linear relationship between luminance and each, discomfort and disability glare, although they are not equal.
UTRI-99-36
SUBJECTIVE AND OBJECTIVEASPECTS OF HEADLAMP GLARE:EFFECTS OF SIZE AND SPECTRALPOWER DISTRIBUTION
"As expected, both the threshold luminances for detection of the pedestrian target (themeasure of disability glare) and the numerical estimates of discomfort generated by the subjects(the measure of discomfort glare) increased with higher glare illuminances..."
"For the disability measure the models were linearrelationships between luminance thresholds and illuminance; for the discomfort measure theywere linear relationships between log discomfort ratings and log illuminance."

The following study disagrees with the above and states that there is a direct relationship to luminance and disability glare, but other factors also come into play regarding discomfort glare.
The authors briefly touch on loss of peripheral vision (an important safety consideration) as a result of glare, and one of their conclusions is:
Since glare illuminance is the most important factor in predicting both disabilityand discomfort glare, it might be important to revisit luminous intensity limitations for lampswith greater ability to cause glare. Approaches such as leveling systems might be importantcomponents to limitations of glare from these lamps.
National Highway Traffic and Safety Administration DOT 809 672 October 2003An Investigation of HeadlampGlare:
https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/final-report_rpi_glare_spectrum.pdf
 
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-Virgil-

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I searched UMTRI and found a limited number of articles using headlight and using glare as search terms. They were old, and their references were older yet. Many from the 1970's and older.

Keep searching; there's an enormous amount of research from the last two, five, ten, fifteen, twenty years.
 

Poppy

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You may also be able to find some glare articles here:

https://www.lrc.rpi.edu/programs/transportation/publications.asp
SubLGT,
Thank you, that link is quite helpful.

Gentlemen:
I really want to get a handle on this because, although I have already written to my US Senators, and my Congresswoman, I want to send a followup letter with references to scientific articles. So far I have only gotten an automated response from one senator, at the time they were still involved with the impeachment trial.

As stated above glare has a linear relationship to intensity.
In one of the articles I found, it was stated that a 1 degree change in aim will have a significant impact on intensity and glare.
The below article states that it was measured @ 1.4 degrees and that the impact of HID misalignment is a 2,433% increase over a non-misaligned light.
This is taken from an article that encourages leveling and cleaning systems:
UMTRI-2007-46 NOVEMBER 2007
BENEFITS OF HEADLAMP LEVELING AND
CLEANING FOR CURRENT U.S. LOW BEAMS

Table 2 shows the consequences of misaiming the lamps two standard deviations of
vehicle pitch up on luminous intensities at 0.5° up, 1.5° left. The results indicate that (1) for
the tungsten-halogen lamps, the misaim resulted in a larger increase in luminous intensities
for the 2004 low beams (952%) than for the 1997 low-beams (518%), and (2) for the 2004
lamps, the misaim resulted in a larger increase in luminous intensities for the HID low beams
(2,433%) than for the tungsten-halogen low-beams (952%).
Table 2
Median luminous intensity directed toward 0.5° up, 1.5° left (a glare
test point) from 1997 and 2004 U.S. low beams when aimed nominally
and when misaimed two standard deviations of vehicle pitch up.
Aim
Lamps
Nominal 1.4° up
Change
1997 T-H 911 cd 5,628 cd +518%
2004 T-H 932 cd 9,808 cd +952%
2004 HID 700 cd 17,733 cd +2,433%

This article:
https://www.sciencedirect.com/science/article/pii/027554089500070T
A 1995 study: [h=1]Night driving: effects of glare from vehicle headlights on motion perception[/h]In part concluded:Elderly drivers often experience disability glare at night from the headlights of oncoming vehicles...
The results show that simulated lens opacities, which have little or no effect on standard day time measures of visual acuity, have a marked effect on night-time measures of contrast sensitivity for moving targets. Taking into account the average luminance of objects lit by road lighting, we estimate that high-beam glare reduces maximum contrast sensitivity by an order of magnitude in persons affected by mild[FONT=NexusSerif, Georgia, Times New Roman, Times, STIXGeneral, Cambria Math, Lucida Sans Unicode, Microsoft Sans Serif, Segoe UI Symbol, Arial Unicode MS, serif] lens opacities, giving a dynamic acuity of 1.0 c/deg (6/180 Snellen equivalent) or less. [/FONT]

[FONT=NexusSerif, Georgia, Times New Roman, Times, STIXGeneral, Cambria Math, Lucida Sans Unicode, Microsoft Sans Serif, Segoe UI Symbol, Arial Unicode MS, serif]My ophthalmologist told me that "everyone" gets cataracts, some sooner than others. Cataracts are lens opacities. The study above found that glare affected older people in their ability to judge the rate of approaching vehicles, and may cause accidents. This was in 1995 (before HID lights) and their recommendation was that older people's vision should be checked for each licensing period.

I have not found any studies that quantify the advantages of increased intensity for better seeing VS the disadvantages of increased intensity producing more glare disability.

If anyone could point me to such a study, that would be appreciated.


[/FONT]
 

Poppy

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the safety benefit from extra seeing light is greater than the safety drawback of extra glare light. Sounds simple, but it's not; there are many interconnected and seemingly contradictory effects at work. For example: it takes a lot more light to increase seeing ability than it does to increase glare. Another example: the placement of light within the beam most likely to provoke favorable opinions of a set of headlamps is least helpful to safety performance/actually helping the driver see. The subject really is very, very complex. For the set of questions you're asking, probably the best single-source document is SAE J2829, which goes into very well-written detail about how the tradeoffs work between seeing and glare, how seeing light increases interact with glare increases, glare characteristics of other cars' lights versus seeing light characteristics of your car's lights, etc. It's an expensive document, but while I haven't looked for this one specifically, it seems almost anything can be found if you look around/ask around on the internet these days.

An '08 Grand Marquis's headlamps can be upgraded pretty significantly. Suggest you talk to Daniel Stern (search Daniel Stern Lighting and you'll find his site)
Virgil,
Thanks for pointing to that SAE J2893 document, but $81 is about $80 more than I want to spend. :)
In looking for that, though I found this
http://www.unece.org/fileadmin/DAM/trans/doc/2005/wp29gre/gtr8-5e.pdf

I'm a slow reader, and haven't finished reading and absorbing it yet, but there appears to be a bit of good, valuable information in it.
 

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