Mr. Michael Haas

Haas Design Concepts
P.O. Box 575
Tiburon, CA  94920

Dear Mr. Haas:


This responds to your letter asking whether your product, the HAAS Design Concepts sequential perimeter lighting system, is permissible under Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment (49 CFR § 571.108).  As explained below, your product is permissible if it operates in a manner that is synchronized with the vehicle’s required turn signals and satisfies the other criteria cited in this letter.

By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized under the National Traffic and Motor Vehicle Safety Act (49 U.S.C. Chapter 301) to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment.  NHTSA does not provide approvals of motor vehicles or motor vehicle equipment.  Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture, before the product can be offered for sale.  Manufacturers must also ensure their products are free of safety-related defects.   

The following interpretation of FMVSS No. 108 is based on our understanding of the information provided in your letter, and is limited to the system you described. 

Description of Your Product

From your letter and follow-up correspondence with my staff, we understand that your product consists of a strip of 24 amber-colored LEDs that are mounted inside a 30-inch long “Metalized Plastic rail.”[1]  This rail would be attached horizontally along the lower portion of the exterior of a vehicle’s driver and front passenger doors with “two-sided automotive acid rain tape.”  The LED strip would be wired into a “Sequential Controller” through a hole in the door panel.  This Sequential Controller in turn would be “fastened” to the vehicle’s existing turn signal system.

We understand that your product operates as follows:  When the headlamps are activated, all 24 of your product’s LEDs illuminate as steady-burning lamps.  When the driver activates the left or right turn signals, the amber-colored LEDs on the corresponding side become brighter sequentially from the “front” end of the rail (i.e., the end nearer to the front of the car) to the rear end of the rail.  It is our understanding that this sequential turn signal function can be activated regardless of whether the headlamp system is on or off, the only difference being the initial brightness of the LEDs (dim vs. off).  You state that your product’s cycle of sequentially activating LEDs is timed so that the cycle restarts at a rate that matches the flash rate of the required turn signals, and that if the turn signal is cancelled, the LEDs immediately return to their steady-burning (or “off”) state even if they are only partway through a cycle.

Applicable Requirements

Motor vehicle lighting that is installed as original equipment is regulated under FMVSS No. 108.  FMVSS No. 108 requires that vehicles be equipped with certain types of lamps (“required” lamps), and sets out specific performance standards that those lamps must meet.  Non-required (or “auxiliary”) lamps, while still regulated under FMVSS No. 108, are not required to meet specific performance requirements in the same way that the required lamps are.  Rather, auxiliary lamps are subject to S6.2.1, which states: “No additional lamp, reflective device, or other motor vehicle equipment is permitted to be installed that impairs the effectiveness of lighting equipment required by this standard.”

NHTSA has issued numerous interpretations on the meaning of the phrase “impairs the effectiveness” in S6.2.1.  For example, an auxiliary lamp impairs the effectiveness of required lighting equipment if it causes “confusion with the signal sent by another [required] lamp.”[2]  Further, an auxiliary lamp that supplements a specific required lamp should “perform in the same manner, and perform the same function, as the original equipment it is intended to supplement.”[3]  The question of whether an auxiliary lamp impairs required lighting equipment is usually decided on a case-by-case basis. 


We do not believe that your product would impair the effectiveness of a vehicle’s required lighting equipment in either its steady-burning state or when it sequentially flashes for signaling purposes.  Please note, however, that your product may need to conform to certain requirements relating to the vehicle’s hazard warning system, depending on whether your product activates with the vehicle’s hazard warning lamps.

We do not believe that your product would impair the effectiveness of required lamps in its steady-burning state because it operates in a way that is consistent with FMVSS No. 108’s requirements for a side marker lamp (which is the type of signal lamp your product most closely resembles).[4]  Specifically, your product activates when the vehicle’s headlamp system is
activated.  Its LEDs are steady-burning except when they flash as part of the turn signal system.  Furthermore, the LEDs are amber, which we have previously determined is the only appropriate color for auxiliary side marker lamps that are located towards the front end of the vehicle.[5]

We also do not believe that your product would impair the effectiveness of the vehicle’s required turn signals when flashing for signaling purposes because your product’s cycle of sequentially illuminating its LEDs repeats at a rate that is synchronized to the required turn lamps.[6]  The illumination sequence restarts in time with each flash of the required turn signal lamps, and when the turn signal is cancelled, your product returns to a steady-burning state (or turns off) immediately.[7] 

Although you do not discuss your product’s functionality as a hazard lamp in your interpretation request, we believe it is possible that, depending on how your product is wired, its LEDs may activate as part of the vehicle’s hazard warning system.  If this is the case, your product would need to meet additional requirements to ensure it does not impair the effectiveness of the vehicle’s hazard lamps.  S6.6.2 of FMVSS No. 108 requires a “vehicular hazard warning [signal] operating unit,” [8] which is defined in S4 as “a driver-controlled device which causes all required turn signal lamps to flash simultaneously to indicate to approaching drivers the presence of a vehicle hazard.”  Although your product is not a “required turn signal lamp,” if it is activated as part of the vehicular hazard warning signal system, its LEDs would need to flash simultaneously when the hazard warning lights are activated to be permissible under FMVSS No. 108.  If the LEDs illuminate sequentially rather than “simultaneously,” it could cause driver confusion and could potentially interfere with the effectiveness of the hazard warning system.

Lamp Brightness

            Separate from your product’s sequential activation pattern, we are concerned that the brightness of your product’s LEDs could potentially impair the vehicle’s required signal lamps.  Specifically, if the LEDs are too bright, it could obscure the vehicle’s required signal lamps, or could cause other drivers not to recognize that your product supplements the vehicle’s required turn signals.  To avoid the possibility of impairment due to brightness, it is our view that a supplemental signal lamp such as your product should not be noticeably brighter than the required lamps that it supplements.  Note that, because the question of impairment should be analyzed on a vehicle-by-vehicle basis, the maximum brightness of as auxiliary signal lamp on a particular vehicle must be determined based on the brightness of the required signal lamps that are actually installed as original equipment on that vehicle—even if FMVSS No. 108 permits signal lamps of that type to be brighter.

Make Inoperative Provision

Please note that your product would be subject to the Safety Act’s “make inoperative” provision (49 U.S.C. § 30122).  The “make inoperative” provision prohibits manufacturers, distributors, dealers, rental companies and motor vehicle repair businesses from “knowingly mak[ing] 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 by NHTSA.  If a business that falls into one of these categories were to install your product on a vehicle in a way that interferes with a vehicle’s required lighting or otherwise renders a vehicle’s other safety features inoperative, that entity could be subject to a NHTSA enforcement action.  Historically, NHTSA has viewed the “impairment” and “make inoperative” standards as identical (i.e., lighting equipment that is prohibited under the impairment provision would also be prohibited under the make inoperative provision, and vice versa).[9]

If you have further questions, you may refer them to Daniel Koblenz of my staff at (202) 366-2992.






                                                                                    Jonathan C. Morrison

                                                                                    Chief Counsel



Dated: 5/6/19

Ref: FMVSS No. 108




[1] You explain that these LEDs “are sealed by clear-colored cocking inside the cap rail which are protected from the elements by Smoke Colored Polycarbonate plastic covers,” and that the polycarbonate material you use to cover your product’s LEDs “is similar to the polycarbonate used to protect all automotive head lights and tail lights.”  We would like to point out that the polycarbonate that is typically used to protect required lighting cannot meet the requirements of S14.4.2 without some sort of protective coating. 

[2] Letter to Byung M. Soh (Sept. 13, 1988), available at

[3] Letter to Mr. Bart W. Hill (Aug. 27, 1999), available at

[4] Letter to Robert M. Currie (Jan. 31, 1997), available at

[5] Letter to Robert J. Ponticelli (Aug. 18, 1995), available at

[6] Letter to Jerry Koh (Feb. 6, 1986), available at 

[7] We note that side marker lamps do not need to flash simultaneously with required turn lamps to be synchronized.  See letter to Warren M. Heath (Dec. 23, 1969), available at    

[8] The text of S6.6.2 uses the term “vehicular hazard warning operating unit,” which inadvertently omits the word “signal.”

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