Paul Schaye
CEO, Pedestrian Safety Solutions
245 Park Avenue, 41st Floor
New York, NY 10167

Dear Mr. Schaye:

This responds to your letter requesting an interpretation of whether your auxiliary lamp, the Auto Motion Alert (“your product”), is permissible under Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, reflective devices, and associated equipment.  Because your product would be installed as aftermarket equipment, not as original equipment, and would not replace original equipment, and because FMVSS No. 108 applies only to equipment installed as original equipment or that replaces original equipment, we have interpreted your request as asking whether the installation of your product is permissible under the “make inoperative” provision of the National Traffic and Motor Vehicle Safety Act of 1966 (the Safety Act).  The Safety Act prohibits most automotive businesses from installing aftermarket lighting equipment if doing so would take the vehicle out of compliance with FMVSS No. 108.  For auxiliary lamps, the primary restriction imposed by FMVSS No. 108 is that the lamps cannot impair the effectiveness of a vehicle’s required lighting equipment.

We have tentatively concluded that your product is unlikely to impair the effectiveness of required lighting equipment, and is therefore unlikely to violate the “make inoperative” provision.  However, we wish to emphasize that the existence of impairment would depend on the context in which your lamp is used, and thus must be determined on a case-by-case basis.  It is the responsibility of the business installing your product to determine whether doing so constitutes a “make inoperative” violation. We explain our reasoning below.

Description of your product

You describe your product as a lamp that is designed to be installed above a vehicle’s front license plate using the two top mounting screws.  You state that the purpose of installing the lamps on a vehicle is to communicate to road users ahead of the vehicle whether the vehicle is decelerating, accelerating, or maintaining a constant speed.  You state that your product consists of a strip of amber and white LEDs, although you do not provide the exact photometric intensity.  Either the white or amber LEDs are activated, depending upon the underlying condition.  You state that the white LEDs are activated and steadily burn while the vehicle is accelerating or travelling at a constant speed, and that the amber LEDs are activated and steadily burn while the vehicle is decelerating or stopped.  The LEDs are actuated by a microcontroller that detects the vehicle’s acceleration using internal accelerometers.  We also understand, based on our communications with you, that the brightness of the LEDs, the threshold levels of acceleration or deceleration activating the LEDs can be controlled through software, although it is our understanding that the product will be sold as a sealed unit that is not adjustable by the end user. You state that, although the LEDs activate independently of other vehicle systems (including the braking system), your product is powered by either a direct connection to the vehicle’s battery, or a 12-volt DC wire supply that is live when the vehicle is turned on.  The exterior housing consists of a weather-resistant polymer enclosure with gasket type seal. 

Applicable Requirements

Because you state that you intend to sell your product aftermarket, the primary potential restriction on its installation is the Safety Act’s “make inoperative” provision. 49 U.S.C.           § 30122.  The “make inoperative” provision states that manufacturers, distributors, dealers, rental companies and motor vehicle repair businesses may not “knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard” promulgated under the Safety Act.  This means that the businesses subject to the “make inoperative” provision would be prohibited from installing your product on a vehicle if doing so would take the vehicle out of compliance with any FMVSS.  The “make inoperative” provision does not apply vehicle owners, and these owners are not precluded from modifying their vehicle by NHTSA’s statutes or regulations.  State and local laws, however, may impact whether an owner may use a vehicle they have modified in a particular jurisdiction.

NHTSA considers the installation of an aftermarket lamp to violate the “make inoperative” provision if the installation of the same lamp as original equipment would violate FMVSS No. 108.[1]  As a non-required (“auxiliary”) lamp, your product is not required to meet any of the performance requirements in FMVSS No. 108 that it would need to meet if it were installed as original equipment.[2]  However, your product would be prohibited under FMVSS No. 108 (and thus, would violate the “make inoperative” provision) if it would “impair[] the effectiveness of lighting equipment required by this standard.” FMVSS No. 108, S6.2.1.    

Because the existence of impairment is, in part, a function of the context in which an auxiliary lamp is used, impairment must be determined on a case-by-case basis.  If a business subject to the “make inoperative” provision installs an aftermarket auxiliary lamp, that entity is responsible for determining whether doing so causes impairment.  If NHTSA determines that a business to which the “make inoperative” provision applies has impaired the effectiveness of required lamps, that business would be subject to a fine of up to $22,329 per violation.[3]  


Based on the information you provided in your interpretation request, we have tentatively concluded that your product, if configured and installed in conformance with the restrictions described in letter, is unlikely to impair the effectiveness of a vehicle’s required lighting, and its installation on a vehicle would be unlikely to constitute a “make inoperative” violation.  There are four aspects of auxiliary lamps that are relevant to impairment: brightness (i.e., photometric intensity), color, location, and activation pattern.  What follows is a brief explanation of NHTSA’s safety concerns for each of these characteristics, along with examples of instances in which the agency would consider an auxiliary lamp to violate the impairment prohibition.  It should be noted that determining whether an auxiliary lamp impairs the effectiveness of required lamps involves a holistic assessment of the context in which the auxiliary lamps are used, and the examples provided are not exhaustive.  Thus, although this letter discusses these four characteristics separately, they should not be considered in isolation, nor should they be considered an exhaustive list of all the considerations that should be taken into account when making an impairment determination.

Brightness (Photometric Intensity)

NHTSA interprets the impairment provision to prohibit auxiliary lamps that are so bright as to obscure or distract from a vehicle’s required lamps.  For example, NHTSA has in the past stated that auxiliary lamps that were so bright as to “mask” adjacent required turning signal lamps would be prohibited due to impairment.[4]   While you do not state the precise brightness of your product, you state that its brightness “is limited and so would not impair or mask the vehicle’s headlamps or turn signals.”  Although the extent to which your product would interfere with a vehicle’s required lighting may vary depending on the design and performance of a particular vehicle’s required lamps, we do not believe your product would impair the effectiveness of a vehicle’s required lamps on the basis of brightness if its photometric intensity is sufficiently limited such that your product’s LEDs are noticeably dimmer than the vehicle’s required head lamps and front turn signal lamps.


NHTSA interprets the “impairment” provision to prohibit auxiliary lamps that are colors the agency believes are likely to cause confusion to other road users.  For auxiliary lamps located on the front of the vehicle, colors that could cause confusion include red (which could be confused for a tail lamp), green (which could be confused for a traffic signal), and blue (which could be confused for a law enforcement vehicle).  By contrast, we have consistently said that amber and white lamps are permissible on the front of the vehicle.[5]  Because your product illuminates as either amber or white, depending on the underlying condition, we do not believe your product would impair a vehicle’s required lamps on the basis of color.


NHTSA interprets the “impairment” provision to prohibit auxiliary lamps that are mounted in locations that cause them to interfere with the ability of a vehicle’s required lamps to achieve their purpose. For example, NHTSA has stated in the past that auxiliary lamps placed too close to FMVSS No. 108-compliant identification lamps would be prohibited because they may confuse other road users.[6]  The agency has long maintained that highway traffic safety is enhanced by the familiarity of drivers with established lighting schemes, which facilitates their ability to instantly recognize the meaning the lamps convey and respond accordingly. Therefore, any auxiliary lighting on the front of a vehicle must be located such that it would not interfere or be confused with other required lamps.  Your product is designed to be no wider than a license plate.  In the case where a license plate holder is mounted at the centerline of the vehicle at a lower mounting height than the vehicle’s required lamps, we think your product would, in most cases, be unlikely to interfere with the required lamps’ ability to achieve their function based on proximity.  However, we note that if a vehicle’s front license plate were located somewhere other than the centerline of the front bumper, and especially if it were located near a vehicle’s required lamps, it would be likely that the installation of your product on the front license plate holder would cause impairment.  Our determination in this letter that your product would be unlikely to impair the effectiveness of required lamps on the basis of mounting location assumes that your product is mounted on front centerline of the vehicle.  If your product were mounted somewhere other than the front centerline of the vehicle, we believe that it would be more likely to impair the effectiveness of the vehicle’s required lamps.

Activation Pattern

NHTSA interprets FMVSS No. 108 to require that all auxiliary lamps be “steady burning,” with the sole exception being auxiliary lamps that supplement required lamps that flash, such as turn signals.[7]  While this requirement has been relatively straight-forward to apply in the past, the introduction of new, programable lighting devices (such as your product) that are intended to communicate driver intent to other road users, has convinced the agency that it is necessary to clarify the meaning of “steady burning.”  To this end, we are clarifying here that the requirement that auxiliary lamps be steady burning does not mean that an auxiliary lamp is prohibited from being activated or deactivated automatically.  Rather, it means that the lamp must be steady burning when activated, and that the event that triggers its activation or deactivation (in this case, the vehicle’s rate of acceleration or deceleration exceeding a certain minimum threshold) cannot be so frequent or random that the lamp would distract or confuse other road users.  For example, a lamp that activated and deactivated on an extremely short time interval due to sensitivity to slight changes in the underlying conditions, would not be considered steady-burning.[8]  More traditional examples of lamps that are not steady-burning include, but are not limited to, strobes and turn signals.  By contrast, an auxiliary lamp that gradually changes in intensity based on ambient lighting conditions may be considered steady burning.[9] 

We have determined that your product would likely be considered steady burning because the event that triggers the activation of the LEDs—the deceleration of the vehicle—is likely not something that occurs so frequently or randomly that it would cause your product to appear to flash, which could confuse or distract other road users.  We note that this determination rests on the assumption that your product’s accelerometer is calibrated not to be overly sensitive to small changes in acceleration.    

We acknowledge that this interpretation supersedes some of our prior, more restrictive interpretations of the concept of “impairment.”  In particular, this letter specifically supersedes our previous interpretation concluding that all auxiliary lamps used to communicate “non-standard signals” (i.e., information other than what is communicated by required lamps) to other drivers would categorically impair the effectiveness of a vehicle’s required lamps.[10]  We reiterate, however, that auxiliary lamps may not be used to communicate non-standard signals (or, in fact, any signals) if doing so impairs the effectiveness of required lighting. 

Other Considerations

You should be aware that, even if your product is permissible under FMVSS No. 108 and the “make inoperative” provision, it is possible that State and local laws or restrictions may apply to your product. You may wish to consult the State and local transportation authorities in the areas you intend to market your product to make sure it is permissible under these laws. 


Finally, regardless of whether your product is subject to the restrictions of FMVSS No. 108 or the “make inoperative” provision, please be aware that if you or this agency finds your product to contain a safety-related defect after you market the product, you are responsible for conducting a notice and recall campaign as required under 49 U.S.C. §§ 30118-30120.


            If you have further questions, please contact Daniel Koblenz of my staff at 202-366-2992.






Jonathan C. Morrison
Chief Counsel


Dated: 9/9/19

Ref: FMVSS No. 108


[1] E.g., Letter to Timothy C. Murphy (Nov. 1, 2004), available at

[2] We note that auxiliary lamps that use plastic optical materials must comply with S14.1.2, and are subject to various other minor restrictions that are not relevant here.

[3] See 49 CFR part 578.

[4] E.g., Letter to Mark Wallach (Oct. 17, 2006), available at

[5] E.g., Letter to Anthony M. Cooke (Oct. 19, 2006), available at

[6] E.g., Letter to [REDACTED] (Jan. 21, 2004), available at

[7] Prior to 2007, FMVSS No. 108 included an explicit requirement that, with the exception of certain types of required lamps (e.g., turn signal lamps), all lamps on a vehicle, including auxiliary lamps, must be steady burning.  In 2007, NHTSA implemented an administrative reorganization of FMVSS No. 108 which, among other things, converted the blanket “steady burning” requirement (and its exceptions) into individual activation requirements for each type of required lamp.  See 72 FR 68234 (Dec. 4, 2007).  Although the reorganized rule no longer includes a blanket “steady burning” requirement, NHTSA stated in the preamble to the reorganized rule that its “rewrite of FMVSS No. 108 is considered administrative in nature because the standard’s existing requirements and obligations are not being increased, decreased, or substantively modified.” Moreover, NHTSA continues to believe that flashing auxiliary lamps would impair the effectiveness of required lamps by distracting or confusing other road users.

[8] E.g., Letter to Timothy C. Murphy (Nov. 1, 2004), available at

[9] E.g., Letter to Ian Goldstein (July 21, 1998), available at

[10] E.g., Letter to Kerry Legg (Feb. 21, 2008), available at