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Thread: Too-Bright Headlights & Fog-Lamp Questions

  1. #31

    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by pungo View Post
    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?
    Quote Originally Posted by -Virgil- View Post
    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.

  2. #32

    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by pungo View Post
    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.

  3. #33
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    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.
    Last edited by jeffsf; 03-04-2020 at 02:26 PM.

  4. #34

    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    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.

  5. #35
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Thanks Jeff, you explaned that so clearly.
    Can you come over and talk me through the Contract of Sale for our new house please?
    P
    "O frabjous day! Callooh! Callay!" He chortled in his joy.

  6. #36
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by -Virgil- View Post
    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-re...text=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.do...e_spectrum.pdf
    Last edited by Poppy; 02-22-2020 at 09:15 AM.
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  7. #37
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by Poppy View Post
    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.
    You may also be able to find some glare articles here:

    https://www.lrc.rpi.edu/programs/tra...blications.asp

  8. #38

    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by Poppy View Post
    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.

  9. #39
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by SubLGT View Post
    You may also be able to find some glare articles here:

    https://www.lrc.rpi.edu/programs/tra...blications.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/scienc...7554089500070T
    A 1995 study: Night driving: effects of glare from vehicle headlights on motion perception

    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 lens opacities, giving a dynamic acuity of 1.0 c/deg (6/180 Snellen equivalent) or less.

    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.


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  10. #40
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by -Virgil- View Post
    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/t...re/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.
    My Grand Kids call me Poppy

  11. #41
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Quote Originally Posted by -Virgil- View Post
    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,
    Awesome recommendation!

    I found his site. http://www.danielsternlighting.com/

    In 2001-2002, the US Federal Government's Department of Transportation's National Highway Traffic Safety Administration (NHTSA) was nominally considering changing the headlamp performance standards contained in Federal Motor Vehicle Safety Standard 108.

    His response to questions raised during the comment period is intellectual, and well referenced.
    find his response here


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  12. #42

    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    It's a good read, for sure, and responsive, in its own way, to the questions that NHTSA asked. Unfortunately that NHTSA initiative, such as it was, never went anywhere. Some UMTRI reports worth reading and understanding(!) on the subject include this one (even if you only read the abstract, the important part is in there: longer seeing distance when your car and the opposing car both have high beams on -- this is the nub of the question we're tossing around here), this one and this one. And here is a good article.

    As far as the actual "money quote" about safety likely improving if everyone used high beams, I know it's in several papers published over the last few decades, but (natch!) I can't put my hands on them at the moment. This is not unusual, but it is frustrating. I'll keep sifting and looking, but that first linked paper in the paragraph above this one says exactly that, just in different words.

  13. #43
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Virgil challenged me to do some research, and so I did. I estimate that I spent about 20 hours locating and reading articles pertinent to the discussion at hand. This is far from my profession, and therefore I skipped through some of the details. This is what I found.

    The term Blinded, or Blindness, is not mentioned in the literature. Instead terms like "seeing distance" and "glare" are the predominate terms used. Glare is further broken down to: "Glare Disability" (where one may not be able to see a pedestrian), "Glare Discomfort" (which may cause aberrant behavior of a driver who tries to avoid it), and "Flash Glare" (where the beam of the light may cause additional glare due to undulations of the road.

    Studies vary, but headlight mis-aim ranges from 24% to 39% of the vehicles on the road at the time of the studies performed. Unfortunately I don't know what year those studies were performed.

    Studies also disagree about whether older people are more affected by glare then younger people.
    The science of the physiological changes in the eye as it ages (lens opacities (cataracts), and artifacts within the aqueous humor) produce more glare within the eye itself.
    Also the fact that the cilliary reflex slows typically with age. Means that older people's eyes respond more slowly to glare. If their pupils are dilated, they'll let more light in for a longer period of time than younger people.

    The blue white lights don't produce more seeing distance, but they do produce more glare, especially for the older people. In other words, color temperature affects older people more than younger.

    Gotta run... more later.
    Last edited by Poppy; 03-14-2020 at 04:49 AM.
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  14. #44
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    Default Re: Too-Bright Headlights & Fog-Lamp Questions

    Its been stated, I don't know if it has been studied, that changes in the periphery (such as a bright light) cause a person to look at it to determine if it is a threat. There are a number of crashes into stopped patrol cars each year, and often the defending attorney blames the flashing lights - that his client was drawn to the lights like a moth is drawn to a light. As a case study, I have found that I DO initially look at, almost stare at, oncoming glaring lights. I have learned to turn away (look down and to the right) from them. If I don't look away quickly enough, my pupils will have constricted, and I will have decreased seeing distance until my pupils once again dilate. A number of authors stated that there needs to be more studies on the deleterious affects of drivers response to glare.

    Us standards allow a more horizontal aim compared to European standards which are aimed slightly downward. In America the standards are not highly enforced, and one in four, to two in five vehicles have mis-aligned headlights, whereas, in Europe their standards are strictly enforced, and their aim is to reduce glare. This results in a very disproportionate number of vehicles in the US producing glare than in Europe. One study found that Americans are more tolerant of glare, because they got fewer dimming requests. The authors did not take into account that people will report outliers, ie make a dimming request when it is one in 100 vehicles, that produce excessive glare. But when one in five produce excessive glare due to mis-aim, and 90% produce flash glare do to road undulations, people just suffer with it, or worse... drive with their glaring high beams on!

    More than one study found there there is a disproportionate number of pedestrian fatalities caused by off the road crashes at night than during the day. The authors for the most part cited insufficient seeing distance, and some cited alcohol consumption and fatigue as possible confounders.

    As stated above, it takes more lumins to create more seeing light, than it does to create more glare. Also the intensity of the beam determines seeing distance. As the intensity of the beam is increased to increase the seeing distance, it is increasingly important to assure that it is aimed such that it does not come in the direct line of site of oncoming traffic. It appears to me that without adaptive lighting, flash glare as a result of undulations in the road will continue to be a problem, and
    as stated in.
    Since glare illuminance is the most important factor in predicting both disability and discomfort glare, it might be important to revisit luminous intensity limitations for lamps with greater ability to cause glare. Approaches such as leveling systems might be important components 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.do...e_spectrum.pdf
    I am glad that Virgil encouraged me to do some additional research because I now have a better understanding of the issue.
    My Grand Kids call me Poppy

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