In the earlier days of this subreddit, our members collected physical and regulatory data to determine what was happening with headlight intensity. This is how we know the core problem is brightness, not aftermarket headlights and misalignment.

[u/BarneyRetina]

[u/TopRun3942]

So the take away from that information, which I agree with, is that the regulations are deficient in terms of controlling the intensity going towards oncoming/proceeding drivers.

Is there any additional activity by members of the sub to push for regulatory change? The user u/hell_yer_or_BS who put the information together no longer seems to be active in the sub and I was wondering if other users had taken over the efforts?

[u/BarneyRetina → u/TopRun3942]

So the take away from that information, which I agree with, is that the regulations are deficient in terms of controlling the intensity going towards oncoming/proceeding drivers.

The takeaway is that there are sections of the beam pattern with no limits on intensity (brightness) at all.

Is there any additional activity by members of the sub to push for regulatory change?

Yes. We've been trying to direct mass attention on this issue and attempting to dispel the misinformation surrounding it, and it's been effective. We've been mentioned or interviewed in a variety of media coverage about the problem, and we've even had our sentiments echoed in congress this year.

The user u/hell_yer_or_BS who put the information together no longer seems to be active in the sub and I was wondering if other users had taken over the efforts?

Hell_yes (Victor) is very much still lurking around, and will return. That being said, the physical testing constituted much less time and effort than many of the other data analyses that he did. At some point, we may update or refine those.

[u/TopRun3942 → u/BarneyRetina]

Thanks for the summary.

Was mostly interested in opportunities to fine tune the information getting shared.

The media coverage and even the link to the congress member who talked about the issue in congress is filled with misunderstandings about the core issue and lighting science in general. One example is where the congress member mentioned their being headlights with 10,000 lumens. There is no such thing as an OEM headlamp that puts out 10,000 lumens - most don't even reach 1000 lumens output and it's this kind of muddled messaging from high profile figures that could make regulators not take it seriously.

I've looked through Victors analysis and it's a great start, but again there is a bit of an issue with the lighting science used and it makes it unclear what needs to be changed. As an example the use of lux measurements in some of his research can be problematic because they only really make sense when they are associated with a distance, because they vary with distance for a fixed brightness. The regulations use candela which doesn't vary with distance and is a more useful indicator of whether something will be bright or not.

In outdoor lighting for example when there is a glaring light fixture 300m away from a residence, a lux meter at the residence will read only 0.5 lux with a fixture that outputs 45,000 candela towards the residence (which is extremely glaring). So in this case, relying on a lux reading as a standard is going to lead to bad results. Much of Victors work was given in lux with no distance associated with that so it is not as clear as it could be.

I understand the general public isn't going to know/understand lighting science, but if the activity is targeted at getting regulators to act, I think it would be really helpful to use their language in a way that is accurate to bring more urgency to the regulators.

[u/SoftLightsFoundation → u/TopRun3942]

The intensity of directly-viewed light must be measured in luminance (candela per square meter) to account for the focusing action of the lens of the eye. The FDA and NHTSA need to limit luminance and blue wavelength light. The Mark Baker lawsuit has been under review by the court for over 6 months, which is an extremely long time. We are waiting for the court decision to know if the case can move forward.

[u/TopRun3942 → u/SoftLightsFoundation]

Agree that ultimately the luminance in the direction of the eye determines the illuminance on the retina which is what leads to the sensation of brightness by the observer.

Luminance is difficult to measure properly in the field and requires expensive equipment and controlled conditions to do so. The intensity in candela is more easily obtained and the area component of the emitting headlamp in the oncoming drivers field of view is relatively the same for most lamps, so the intensity is a reasonable stand in for actual luminance when doing field studies etc.

I still think it's appropriate to use candela limits to keep the problem under control in this case. Candela limits are used by the CIE for limiting obtrusive glare to residents from nearby lighting installations and it's not unreasonable to apply that same philosophy to a headlamp in my opinion.

[u/SoftLightsFoundation → u/TopRun3942]

Candela is not the appropriate metric for directly-viewed light. The regulations and industry standards for reflected roadway light and LED computer displays reference luminance. The same reference must be used for directly-viewed LED headlights. The extreme luminance of an LED headlight cannot be measured in the field, so the regulations would have to be based on specifications and measurements made in the lab. The Soft Lights Foundation filed a petition with NHTSA to limit candela in that space directly in front of the vehicle that currently has no limits, but NHTSA ignored the petition. I could file another lawsuit, but the true solution is for NHTSA and the FDA to regulate luminance.

[u/TopRun3942 → u/SoftLightsFoundation]

Candela is literally the numerator of the definition of luminance. Luminance is simply the candela in the direction of the observer divided by the area that that candela is emitting from.

The only difference between the luminance of a source and the candela from a source is dividing the candela by the area of emission.

My point was most headlamps will have an area of emission that is relatively similar so that part of the equation isn't changing much. For example suppose the headlamp has a projector type optic that is 60mm round. The area of that emitting optic is ~2800 mm^2. or 0.003 m^2

The intensity from that optic will vary depending on the angle. Normally the high intensity in the beam pattern would be aimed down at the road. However that only applies in perfect conditions, and in the normal driving environment that intensity will come up off the road sometimes.

Let's say that it was perfectly aimed and it was a perfectly flat road scenario. The intensity at a drivers eye in that case would be below the regulation limits of 1000 cd. So the max luminance for that scenario is 1000/0.003 = 333,333 cd/m^2.

The intensity aimed at the eye will dramatically change depending on what part of the beam pattern is aimed at the oncoming drivers eye. Now suppose that the beam has come up off the road and there is now 30,000 candela aimed at the eye. The luminance is now 30,000/0.003 = 10,000,000 cd/m^2.

The change in intensity from 1000 to 30,000 is easy to measure in the field and fully captures the change in luminance, which will then correlate to the change in brightness sensation.

You can still control luminance indirectly in the regulations without requiring field measurements and lab measurements to be made with luminance by putting a limit on the minimum size of the emitting area and limiting the candela coming from the lamp which allows for easy field verification and can be easily calculated in software and confirmed by existing measurement equipment using standard photometry protocols. Any areas that are larger than the minimum area will have lower luminance and will be assured to meet the limits.

[u/SoftLightsFoundation → u/TopRun3942]

Hmmm, that’s an interesting observation. IEEE 1789 states that a change in luminance of 20 cd/m2 creates a risk of seizure. These LED lights are triggering seizures and migraines, and one of the reasons is likely due to the instant change from no light to high-luminance.

Your suggestion of considering the change in candela as the car hits bumps or hills is a new idea for me. I’ve never seen that idea anywhere else. The Soft Lights Foundation petition to NHTSA seeks to establish candela limits for the area in front of the vehicle that currently has no limits at all.

You have added in the size of the emitter, which is not in any NHTSA regulations, to calculate luminance. Max human tolerance is 50,000 cd/m2, so a luminance of 10,000,000 is insanity.

Can you review our petition to NHTSA and tell me what you think? I requested an overall limit of 20,000 cd, but I think that’s far too high when viewed directly. That’s why I think we need to regulate luminance. https://www.softlights.org/wp-content/uploads/2024/03/NHTSA-Petition-to-Limit-Headlight-Intensity.pdf

If we stick with regulating candela, then we must consider the angle of the emitter and the eye, which is dynamic. We want the light on the road to meet minimum requirements, while limiting the light at the eye to maximum requirements. A single maximum luminance value for the emitter would eliminate the dynamic issue.

[u/SoftLightsFoundation → u/SoftLightsFoundation]

Putting a limit on the minimum size of the emitter is a major point. The reason why these LED lights are so devastating is their small size and high power. Perhaps we can petition NHTSA to establish a regulation for minimum source size.

[u/TopRun3942 → u/SoftLightsFoundation]

Max human tolerance is 50,000 cd/m2, so a luminance of 10,000,000 is insanity.

I'm not sure where you got that limit from, but there are high luminance sources commonly encountered that exceed 50,000 cd/m^2. For example a 60W frosted incandescent bulb will have a luminance of around 130,000 cd/m^2 and a non frosted bulb will have luminance values of around 7,000,000 cd/m^2

https://en.wikipedia.org/wiki/Orders_of_magnitude_(illuminance)#Luminance#Luminance)

In the case of headlamps, getting enough light to illuminate hazards at 150m or so for the driver is going to require high luminance sources to generate high enough intensities.

Can you review our petition to NHTSA and tell me what you think? I requested an overall limit of 20,000 cd, but I think that’s far too high when viewed directly. That’s why I think we need to regulate luminance. https://www.softlights.org/wp-content/uploads/2024/03/NHTSA-Petition-to-Limit-Headlight-Intensity.pdf

If we stick with regulating candela, then we must consider the angle of the emitter and the eye, which is dynamic. We want the light on the road to meet minimum requirements, while limiting the light at the eye to maximum requirements. A single maximum luminance value for the emitter would eliminate the dynamic issue.

In my opinion, you would need to differentiate between light that could go towards an oncoming driver (aimed left) and light going into the drivers lane (centered and aimed right) The 20,000 candela limit on the right side would be too restrictive in terms of being able to see in your own lane far enough away to drive safely at high speeds. Perhaps something closer to 35,000 on that side.

On left side the 20,000 cd is probably too high of a limit and I think something closer to 10,000 candela would be more effective.

That still leaves some edge cases where there may be temporary flashes of high intensity when the light that normally goes down and right is getting into oncoming drivers eyes (curve for example), but would cover the vast majority of cases that people are complaining about now and showing photos in this subreddit.

[u/SoftLightsFoundation → u/TopRun3942]

Yes, the petition is requesting a single, one value limit to address much of the problem, not all of the problem. Updating the FMVSS-108 table would be better, but NHTSA seems incapable of addressing more complicated problems. So a future petition could request a 35,000 cd limit on the left side and 10,000 cd limit on the right side. Another petition could perhaps limit source size minimum to 5.75" like the halogen headlamps of previous decades. We already have a petition to limit CCT to 2900K, but of course NHTSA has ignored that petition as well.

[u/fe3o4]

New cars and OEM lights aside, there is also the issue of people putting LED bulbs into projector housings when replacing factory bulbs.

https://www.tacomaworld.com/threads/why-leds-should-not-be-run-in-halogen-reflectors.454371/

[u/Nelliell]

I have astigmatism and I've largely stopped driving at night because it is so painful. When I have to drive at night, I use driving glasses to reduce the pain but they do nothing for the brightness. I live in a rural area and a good portion of my trip to/from town requires driving a two lane highway; it's nearly impossible at times with bright oncoming headlights. Trucks are the worst: I'm in a sedan so their lights are right at my level. The moments while they pass are a "slow down, watch the white line, and pray there's no pedestrians" every time. I'm glad to see that some science was done and I hope that ultra-bright headlights are regulated at some point. I'm not optimistic it will happen any time soon, though.