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This news story in Popular Science asks whether car headlights are getting brighter and concludes they are not:

So are headlights actually getting brighter?

The short answer is no—although there was a tweak to headlight regulations in 2008—but multiple factors can cause them to seem brighter.

But their reasoning seems to be entirely based on US regulations about headlight brightness:

Headlights are governed by a overwhelming slew of regulations known as FMVSS 108 that dictate how bright they can be, at a maximum and minimum.

One key point pertains to how much light is allowed above the horizontal plane of the low-beam headlights—picture looking at your headlights from the side of the vehicle, and imagine that light shouldn’t be allowed to escape above a line parallel to the ground that comes out of your headlight covers. “Anything above that horizontal level is supposed to be restricted brightness,” says Matthew Brumbelow, a senior research engineer at the Insurance Institute for Highway Safety, or IIHS.

Though they admit that manufacturing misalignment might represent an unintended way round the rules.

However, many headlight after-market retailers specifically advertise that their kits are much brighter than standard headlights (this from XenonHIDs):

LED headlights are the latest innovation for vehicle forward lighting. They are much brighter than regular halogen headlights

Also rules in other countries are very different from the US ones.

Some observers have argued that LED headlights are too bright:

Have those on new cars become too bright? They have, according to the RAC's research which reveals that 65 per cent of motorists have been dazzled by the latest-technology headlights even when they are dipped.

Is there any observational evidence that headlights are getting brighter in the real world (ie observational evidence, not evidence based on assuming everyone follows the rules)?

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  • It seems to me that the rules restrict how much light is going up, not how much light total. Emit more but make sure it's aimed down--at least until it gets out of alignment or the car hits a bump in the road etc.
    – Loren Pechtel
    Feb 5, 2019 at 15:12
  • Are you asking about actual brightness (the amount of light emitted), or apparent brightness (how bright a human eye perceives it to be)? You can have a reduction in actual brightness but an increase in apparent brightness if you - for example - use LED headlights that concentrate their output into colors that human eyes are especially sensitive to.
    – bta
    Apr 21, 2022 at 1:33
  • @bta I'm interested in objective measurements. They exist for total light output and for the human perceived light output.
    – matt_black
    Apr 21, 2022 at 11:28

1 Answer 1

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Obviously, my source is looking at headlights. However if one has internet access you can look it up. Wikipedia seemed to have the most info in one spot but additional info at other sites would be helpful . Lumens (L) are a measure of the amount of light.

  • Old sealbeams = ?,
  • early halogens = 1550 L
  • later halogens =1820 L
  • newest halogens = 2100 L
  • HID = 2800 to 3500 L
  • LED ads claim up to 10,000 L but the Wiki info did not have actual measurements for them.

So , depending on the time period you choose , headlights are more than 6 times brighter in terms of lumens.

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  • 4
    You can make this a better answer by including the link to the source. But also by addressing how common those new-tech headlights are in the real world as, just because they exist, doesn't prove they are widely used. Answering the tech question and the usage question would make a great answer (if you include your sources as even good answers without sources get rejected here).
    – matt_black
    Feb 7, 2019 at 16:41
  • TO complement matt_black's remark, it would also be useful to date the introduction of each technology.
    – Evargalo
    Feb 8, 2019 at 10:21
  • Magazines like Popular Science and Popular Mechanics are written for entertainment not education. The most important factor is that the stories are interesting not factual. While looking at thousands of references in technical papers , I have never seen these magazines cited. as sources.
    – blacksmith37
    Feb 8, 2019 at 16:55

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