Dear Supporters,

Your efforts to sign and share this petition has resulted in over 41,000 signatures and comments, and our petition is now catching the attention of the news media.  Today, ABC 6 in Philadelphia did a news story on blinding LED headlights, interviewing the Soft Lights Foundation and the Insurance Institute for Highway Safety and highlighting this petition: https://6abc.com/blinding-headlights-bright-lights-while-driving-soft-foundation/13118607/

The IIHS is falsely claiming that LED headlights are simply "misaligned".  We know this to be untrue.  Below is my letter to both the IIHS and NHTSA.

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Dear David Harkey, President, Insurance Institute for Highway Safety, and Ryan Posten, Associate Administrator for Rulemaking, National Highway Traffic Safety Administration,

The Soft Lights Foundation submitted a petition on December 10, 2022 to NHTSA to publish a rule requiring headlight sources to emit light that disperses following an inverse square law.  (https://www.softlights.org/wp-content/uploads/2022/12/NHTSA-Petition-to-Require-Inverse-Square-Law-Lamps.pdf).  NHTSA responded on March 10, 2023 that this petition will be reviewed (https://www.softlights.org/wp-content/uploads/2023/04/NHTSA-Reponse-to-Petition-for-Spatial-Uniformity.pdf).  In addition, the Soft Lights Foundation submitted a petition to the Food and Drug Administration on June 12, 2022 to regulate LED products as required by the 1968 Radiation Control for Health and Safety Act. (https://www.regulations.gov/document/FDA-2022-P-1151-0001)

The FDA has not responded that regulating LED products is an unreasonable idea and NHTSA has not responded that light sources for headlights should not disperse following an inverse square law.  Therefore, we would expect that our petitions would be rapidly approved.  However, this has not happened.  A key reason for this lack of approval is a misunderstanding by NHTSA, the FDA, and IIHS regarding how light disperses for lasers and LEDs.

This article in Wikipedia provides a simple starting point.  Quote: "The inverse-square law generally applies when some force, energy, or other conserved quantity is evenly radiated outward from a point source in three-dimensional space. Since the surface area of a sphere (which is 4πr2) is proportional to the square of the radius, as the emitted radiation gets farther from the source, it is spread out over an area that is increasing in proportion to the square of the distance from the source." - https://en.wikipedia.org/wiki/Inverse-square_law

We must notice that the inverse square law only applies to a "point source" where the energy is "evenly radiated outward".  The example given is the surface of a sphere.  LEDs are not spheres.  LEDs are a flat surface.  The light energy is not radiated outward evenly.  The LED chip is not a point source.  Therefore, the inverse square law does not apply.

Both NHTSA and IIHS have a false belief that all light sources have the same physics.  IIHS states, "All sources of light are governed by the same law that essentially states that intensity of light is reduced exponentially as a surface is moved further away." NHTSA makes a similar statement.  This is untrue.  A lens will focus light.  Sunlight that lands on a piece of paper will simply illuminate the paper.  Sunlight that is sent through a magnifying lens can set the paper on fire.  The tungsten filament source of a 1960s sealed beam headlight follows an inverse square law, but reflective surfaces within the headlight enclosure can focus the light into a more focused beam, which is not following an inverse square law.  A flat surface LED chip acts as a built-in lens because of the lack of curvature.  The light rays emitted by the LED chip overlap and create a narrowly focused beam with little divergence.  At very large distances, the light will eventually be slightly more spread out because the light rays are not perfectly parallel, but light from LEDs does not follow an inverse square law.

Light that follows an inverse square law can be measured with the metric of luminous intensity in candela.  Light from a flat surface such as an LED chip or reflected from a flat surface, can be measured with the metric luminance in candela per square meter.  NHTSA standard FMVSS-108 is only applicable to light sources that follow an inverse square law because FMVSS-108 only uses the metric luminous intensity.  For LED headlights, the metric luminance must be used because LEDs emit the light from a flat surface.  FMVSS-108 makes no mention of peak luminance and thus cannot be applied to LED headlights.

We must also bring attention to the incredible density of light from an LED chip.  The maximum human comfort level for viewing is approximately 300 candela per square meter.  At around 50,000 candela per square meter, a person will find the light to be so intense as to be intolerable.  LED chips used for vehicle headlights emit at least 70,000,000 candela per square meter, capable of causing serious physical, neurological, and psychological harm.  Within the LED beam, the light is spatially non-uniform, following a Lambertian pattern within about 2 degrees in space.  The added phosphor will splay out some of this light, and also give it the so-called whitish color, but the majority of the light is still tightly focused within the narrow beam.  In the photo below, the headlights on the left are tungsten filament headlights that follow an inverse square law.  The headlights on the right are LEDs that do not follow an inverse square law and which also emit an excessive amount of high-glare blue wavelength light.

http://www.softlights.org/wp-content/uploads/2023/04/image.png

The FDA is reviewing our petition to regulate LED products, which includes LED headlights.  While it is taking the FDA an extraordinarily long time to review our petition, our expectation is that the petition will eventually be approved because of the Congressional mandate to regulate LED products and publish performance standards.  We fully expect the FDA to correctly use peak luminance or peak radiance to set restrictions for LEDs, just as the FDA already sets radiance limits for lasers.  Once the FDA publishes performance standards for LEDs that include restrictions on peak luminance, then it would be only logical that IIHS and NHTSA would also be compelled to correctly measure and regulate peak luminance for vehicle headlights.

It makes little sense for IIHS and NHTSA to continue to be misinformed on this issue, as the lack of regulation of peak luminance for LED headlights is already causing serious harm.  We have access to mathematicians and physicists who can provide written statements that attest to the accuracy and validity of our statements.  I encourage you to write to me to open a dialog on this topic so that we can provide whatever additional evidence you need.  For NHTSA, approving our petition to ensure that light sources follow an inverse square law for dispersion will restore some of the safety that was lost when the industry switched to LED headlights.  For IIHS, acknowledging that LED headlights emit a directed beam of spatially non-uniform light will help protect the public and its insurance company members.

Sincerely,

Mark Baker
President
Soft Lights Foundation
www.softlights.org
mbaker@softlights.org