NHTSA Interpretation File Search
Overview
NHTSA's Chief Counsel interprets the statutes that the agency administers and the standards and regulations that it issues. Members of the public may submit requests for interpretation, and the Chief Counsel will respond with a letter of interpretation. These interpretation letters look at the particular facts presented in the question and explain the agency’s opinion on how the law applies given those facts. These letters of interpretation are guidance documents. They do not have the force and effect of law and are not meant to bind the public in any way. They are intended only to provide information to the public regarding existing requirements under the law or agency policies.
Understanding NHTSA’s Online Interpretation Files
NHTSA makes its letters of interpretation available to the public on this webpage.
An interpretation letter represents the opinion of the Chief Counsel based on the facts of individual cases at the time the letter was written. While these letters may be helpful in determining how the agency might answer a question that another person has if that question is similar to a previously considered question, do not assume that a prior interpretation will necessarily apply to your situation.
- Your facts may be sufficiently different from those presented in prior interpretations, such that the agency's answer to you might be different from the answer in the prior interpretation letter;
- Your situation may be completely new to the agency and not addressed in an existing interpretation letter;
- The agency's safety standards or regulations may have changed since the prior interpretation letter was written so that the agency's prior interpretation no longer applies; or
- Some combination of the above, or other, factors.
Searching NHTSA’s Online Interpretation Files
Before beginning a search, it’s important to understand how this online search works. Below we provide some examples of searches you can run. In some cases, the search results may include words similar to what you searched because it utilizes a fuzzy search algorithm.
Single word search
Example: car
Result: Any document containing that word.
Multiple word search
Example: car seat requirements
Result: Any document containing any of these words.
Connector word search
Example: car AND seat AND requirements
Result: Any document containing all of these words.
Note: Search operators such as AND or OR must be in all capital letters.
Phrase in double quotes
Example: "headlamp function"
Result: Any document with that phrase.
Conjunctive search
Example: functionally AND minima
Result: Any document with both of those words.
Wildcard
Example: headl*
Result: Any document with a word beginning with those letters (e.g., headlamp, headlight, headlamps).
Example: no*compl*
Result: Any document beginning with the letters “no” followed by the letters “compl” (e.g., noncompliance, non-complying).
Not
Example: headlamp NOT crash
Result: Any document containing the word “headlamp” and not the word “crash.”
Complex searches
You can combine search operators to write more targeted searches.
Note: The database does not currently support phrase searches with wildcards (e.g., “make* inoperative”).
Example: Headl* AND (supplement* OR auxiliary OR impair*)
Result: Any document containing words that are variants of “headlamp” (headlamp, headlights, etc.) and also containing a variant of “supplement” (supplement, supplemental, etc.) or “impair” (impair, impairment, etc.) or the word “auxiliary.”
Search Tool
NHTSA's Interpretation Files Search
| Interpretations | Date |
|---|---|
ID: 08-007826 Testlabs May 15 09OpenDr. Wayne W. Tennesey Testlabs International Ltd. 1797 Logan Avenue Winnipeg, Manitoba Canada R3E 1S9 Dear Dr. Tennesey: This responds to your inquiry regarding the luminous transmittance requirement in Federal Motor Vehicle Safety Standard (FMVSS) No. 205, Glazing Materials. You believe and are concerned that handheld spectrophotometer devices which are used in law enforcement in Canada to determine the percentage of incident light transmitted through vehicle windows may return different results for the same sample. Reliable test results are a crucial part of any test program, and the National Highway Traffic Safety Administration (NHTSA) carefully assesses compliance with the luminous transmittance requirement of FMVSS No. 205 in a manner that provides accurate results. The test that we use is described below. To the extent that you are concerned about the reliability of devices used by localities, your concern should be addressed to the jurisdictions involved. By way of background, NHTSA is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment. NHTSA enforces compliance with the standards by purchasing and testing vehicles and equipment, and we also investigate safety-related defects. The agency has established FMVSS No. 205 (49 CFR 571.205), which specifies performance and marking requirements for various types of glazing. FMVSS No. 205 incorporates by reference American National Standard for Safety Glazing Materials for Glazing Motor Vehicles and Motor Vehicle Equipment Operating on Land Highways-Safety Standard ANSI/SAE Z26.1-1996 (ANSI Z26.1). ANSI Z26.1 specifies that glazing at specific locations shall have at least 70 percent luminous light transmittance, at normal incidence (i.e., with the glazing perpendicular to the measuring device), when measured in accordance with Luminous Transmittance, Test 2 of ANSI Z26.1. Paragraphs 5.1 and 5.2 of Luminous Transmittance, Test 2, specify the sample sizes that are used for the test, the light source to be used, and how to interpret the results. Paragraph 5.1.2 of ANSI Z26.1 states that three specimens of glazing shall be tested for regular luminous transmittance at normal incidence calculated to International Commission on Illumination Illuminant A. The standard further specifies that after the regular luminous transmittance has been determined, the same three specimens shall be subjected to ultraviolet radiation (irradiation), and specifies the lamps that can be used for this irradiation. Paragraph 5.2.3 of ANSI Z26.1 specifies that glazing subject to Luminous Transmittance, Test 2 shall show regular luminous transmittance of not less than 70 percent of the light, at normal incidence, both before and after irradiation. The international standard ISO 3538-1978, Road Vehicles Safety glasses Test methods for optical properties (referenced in section 2.4 of ANSI Z26.1) provides the requirements to be found in equipment to be used for the transmissibility determination. NHTSA safety standards apply to the manufacture and sale of new motor vehicles and motor vehicle equipment. 49 U.S.C. 30112. In the U.S., States regulate the operation (i.e., use) of motor vehicles, and many limit how darkly tinted the glazing may be in vehicles operating in their jurisdictions. It appears that your question relates to the manner in which some Providences are enforcing their luminous transmittance requirements, and thus should be addressed to and answered by the entity that you believe uses an unreliable handheld device. We are not in a position to render an opinion on the means by which a Providence should resolve a disputed test result of a handheld spectrophotometer unit. If you have any further questions, please feel free to contact Sarah Alves of my staff at this address or by telephone at (202) 366-2992. Sincerely yours, Stephen P. Wood Acting Chief Counsel ref:205 d.7/24/09 |
2009 |
ID: 0813Open Mr. Mayo D. Tubbs Dear Mr. Tubbs: We have received your letter of March 23, 1995, asking for a waiver of 49 U.S.C. 30112(a) which will enable the introduction of a new lighting system that you have developed for large trailers. You envision that this system will eventually be installed on emergency vehicles and school buses. We understand that you wish to market this system as original equipment. You have asked that we "provide adequate safeguards to prevent unauthorized dissemination of this information." As Taylor Vinson of this Office explained to you before you wrote, all the agency's letters of interpretation must be made available to the general public, and these letters must include enough information to make the interpretation comprehensible. Mr. Vinson telephoned you on March 30, 1995, and informed you that we proposed, in this instance, to limit the description of the system to the number, location, and quantity of lamps, to withhold the incoming letter with the exception of Attachment A, and to exclude your name and address from the copy made publicly available. You concurred with this treatment of your letter, except that you preferred not to have your name and address withheld in the event a reader might be interested in getting in touch with you. You believe that the current lighting and conspicuity requirements for large trailers are inadequate for safety when compared with your system. This system consists of 18 "strip lights on the side and rear" of large trailers which are "Aviation Green" in color. The side and rear lighting schemes are depicted on Attachment A to your letter. As we interpret Attachment A, two of the strip lights are mounted in the upper right and left rear corners, while eight lights are on each side of the trailer (four right- angle lights in each upper and lower corner, and four lights deployed at one-third body-length intervals at the top and bottom). Motor Vehicle Safety Standard No. 108 Lamps, Reflective Devices, and Associated Equipment is the Federal regulation that governs original lighting equipment on trailers. These requirements must be met upon the manufacture and sale of trailers. With respect to the rear of a van trailer, your Attachment A depicts only strip lights in the upper right and left corners. This is not permissible under Standard No. 108. The Federal regulation requires the conspicuity treatment specified by S5.7 to be applied in this area, as well as clearance lamps. With respect to the side of a van trailer, Standard No. 108 requires horizontal conspicuity treatment to be applied near the lower edge of the trailer as close to the front and rear as practicable, though it need not be continuous as long as it covers at least half the trailer length. Because of the gaps between the strip lights on the trailer side as depicted in Attachment A, it is possible that conspicuity treatment could be applied between the strips that would total half or more of the trailer length. However, supplementary lighting equipment such as your system is not permissible under Standard No. 108 (paragraph S5.1.3) if it impairs the effectiveness of the lighting equipment required by the standard. Standard No. 108 restricts the color of exterior lights to red, amber, and white, the former two of which are associated with caution. Green is not used as an exterior lighting color because it is the recognized signal to proceed rather than to warn. We believe that use of the color green has the potential to create a measure of confusion rather than caution, thereby affecting the effectiveness of the mandatory side lighting equipment, i.e., amber front side markers, red rear side markers, and red and white conspicuity striping or red reflectors. A vehicle manufacturer may petition for a temporary exemption from a Federal motor vehicle safety standard under the conditions specified in 49 CFR part 555, a copy of which is enclosed. Therefore, a trailer manufacturer interested in using your system could apply for a 2-year exemption on the basis that the exemption would make easier the development or field evaluation of a new motor vehicle safety feature providing a safety level at least equal to the safety level of the standard. The effect of an exemption is to allow the manufacture and sale of a nonconforming vehicle without violating 49 U.S.C. 30112(a). I am sorry to inform you that the exemption is not available to equipment manufacturers. If you have data that sustains your belief that your system enhances safety, our Office of Research and Development would be interested in corresponding with you. The Associate Administrator of that Office is George Parker. If there are other questions you have, Taylor Vinson will be happy to answer them for you. Sincerely,
Philip R. Recht Chief Counsel ref:108 d:4/13/95
|
1995 |
ID: 0826Open Mr. Jeffrey D. Shetler Dear Mr. Shetler: We are responding to your FAX of March 29, 1995, to Taylor Vinson of this Office. On May 6, 1994, we advised you that a motorcycle headlamp with an upper beam projector on one side of the vertical centerline and a lower beam projector on the other did not comply with Standard No. 108. You now ask whether the headlamp would comply if an exterior housing were installed on the headlamp which "provides the appearance of two headlamps." This modification in the design does not result in a complying headlamp. Regardless of its exterior appearance, the lamp remains a single headlamp incorporating both an upper and lower beam projector. Since both projectors are within a single headlamp, both projectors must be on the vertical centerline, as specified in Table IV of Standard No. 108. Even if the upper and lower beam projectors were in separate units, neither in itself would be a complying headlamp, and hence not a two-lamp system that could be mounted symmetrically about the vertical centerline. Standard No. 108 does not permit motorcycles to have a headlamp system with asymmetrical beam location. If you have any further questions, you may refer them to Taylor Vinson of this Office (202-366-5263). Sincerely,
Philip R. Recht Acting Chief Counsel ref:109 d:4/24/95
|
1995 |
ID: 0841Open Mr. James M. Hanson Dear Mr. Hanson: This replies to your letter of April 7, 1995, asking for an interpretation of the applicability requirements of paragraph S5.7 of Motor Vehicle Safety Standard No. 108. The conspicuity requirements of S5.7 apply to "each trailer of 80 or more inches overall width and with a GVWR over 10,000 lbs." You state that the word "and" in this paragraph "could cause some trailer manufacturers to think that both conditions must be present before tape is applied on the trailer", and that some manufacturers could interpret this to avoid applying tape to trailers of the specified width but less than the specified GVWR and vice versa. We have no objection to a manufacturer's applying conspicuity treatment to trailers of any width or GVWR. However, as S5.7 clearly states, a manufacturer is not required to comply with the conspicuity requirements unless its trailer is at least 80 inches in overall width and has a GVWR over 10,000 pounds. If you desire further clarification on this matter, you may call Taylor Vinson of this Office (202-366-5263). Sincerely,
John Womack Acting Chief Counsel ref:108 d:4/26/95
|
1995 |
ID: 0849Open Ms. Teresa Thompson Dear Ms. Thompson: We have received your letter of April 6, 1995, with respect to an automotive deceleration signal. You have asked for information "on how to have this product tested and approved as well as information on the legal ramifications and liabilities for the product." The Department of Transportation neither tests nor "approves" products. What it does do is to advise whether motor vehicle equipment is permitted under the statutes and regulations for whose administration it is responsible. In this instance, the appropriate regulation is Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices and Associated Equipment. This standard specifies requirements for only certain items of lighting equipment but it also has an effect on lighting equipment that is not specified in the standard. That is to say, if an item of lighting equipment is not allowable for a manufacturer or dealer to install as original equipment (i.e., equipment on the vehicle at the time of its original sale), in most cases it won't be allowable in the aftermarket for manufacturer or dealer installation on used vehicles as well. As you describe it, the signal is provided by "a strobe light with an independent power supply, which upon heavy breaking (sic), will activate a strobe for five seconds and on impact for ten minutes." The prototype "is approximately 4" by 3" and may be attached to a rear window." Federal laws cover brake activation of your strobe signal. Standard No. 108 requires turn signal lamps, hazard warning signal lamps, and school bus warning lamps to flash. Headlamps and side marker lamps may be flashed for signaling purposes. But all other lamps provided as original equipment must be steady-burning. We regard a strobe lamp as one that flashes. For this reason, the deceleration signal you describe could not be installed as original equipment. Further, its installation on a used vehicle would take the vehicle out of compliance with Standard No. 108. Notwithstanding the discussion above, there is no Federal prohibition on the sale of the strobe signal device, and Federal law does not prevent the vehicle owner from installing it on a used vehicle (however, manufacturers, dealers, distributors, and motor vehicle repair businesses may not do so), no matter what effect the strobe signal may have upon compliance with Standard No. 108. However, the States have the right to decide whether use of the strobe signal is permissible. We aren't able to provide you with information on State laws, and suggest that you seek an opinion from the American Association of Motor Vehicle Administrators, 4600 Wilson Boulevard, Arlington, Va. 22303. We can't advise you on your potential liabilities either, and suggest that you contact your attorney for an opinion on the applicability of local law. In addition, it is important to note that Standard No. 108 prohibits supplementary original lighting equipment that impairs the effectiveness of the original lighting equipment required by Standard No. 108. The proximity of your strobe device in the rear window to the center highmounted stop lamp required by Standard No. 108 raises the possibility of impairment, especially if the strobe is of a color other than red, or so bright as to mask the center stop lamp signal. I am sorry to be unable to offer you more encouragement at present, as we share your concern with the negative effects of fog and rain on drivers and vehicles. It is obvious that you have given much thought to this problem. Noting that you are testing a prototype, this agency would be interested in receiving any data you have or may develop showing a positive effect of the strobe signal upon the frequency and severity of rear end collisions. You may send this to Michael Perel, Office of Research and Development, NHTSA, Room 6206, 400 Seventh St. SW, Washington, DC 20590. It is conceivable that at some time in the future we would allow the center stop lamp to flash under conditions of rapid deceleration. This could open the way to permissibility of an additional lamp such as yours. I note that, to the extent that your device were only to activate upon impact and not during conditions of rapid deceleration, it would not be prohibited by Standard No. 108. Such a device would be permissible as a supplement to, or substitute for, a vehicle's hazard warning signal system. We do not know whether it would be permissible under State laws (see discussion above). If you have any further questions, you may refer them to Taylor Vinson of this Office (202-366-5263). Sincerely,
John Womack Acting Chief Counsel refL108 d:5/11/95
|
1995 |
ID: 0854Open Mr. Lance Tunick Dear Mr. Tunick: This is in reply to your letter of April 14, 1995, to Taylor Vinson of this Office asking for an interpretation of Motor Vehicle Safety Standard No. 108. Specifically, you are concerned with the meaning of the words "outer lens surface" that appear in SAE Standard J586 Stop Lamps for use on Motor Vehicles Less Than 2032 mm in Overall Width FEB84, an SAE standard incorporated by reference in Standard No. 108. These words appear as part of the visibility specifications under the installation requirements. You point out that "outer lens surface" as not been defined either by the SAE or by NHTSA. You believe that the phrase within the context of SAE J586 can mean "light emitting surface" as defined in SAE J387, and ask for confirmation. According to Standard No. 108 (SAE J586), "to be considered visible, the lamp must provide an unobstructed view of the outer lens surface of at least 12.5 square centimeters measured at 45 degrees to the longitudinal axis of the vehicle." SAE Information Report J387 Terminology - Motor Vehicle Lighting OCT88 defines "light emitting surface" as "all or part of the exterior surface of the transparent or translucent lens that encloses the lighting or light signalling device and allows conformance with photometric and calorimetric requirements." We believe that it would be appropriate to substitute the definition of "light emitting surface" for "outer lens surface" in SAE J586. The "outer lens surface" of J586 appears to mean the same as "the exterior surface of the transparent or translucent lens" of J387. Thus, stop lamp visibility conformance would require an unobstructed view of the light emitting surface of at least 12.5 square centimeters. As always, Taylor will be happy to answer any further questions you may have on this matter (202-366-5263). Sincerely, John Womack Acting Chief Counsel ref:108 d:5/3/95 9
|
1995 |
ID: 0857Open Mr. Takashi Adachi Dear Mr. Adachi: This is in reply to your letter of March 14, 1995, to Richard Van Iderstine of this agency, asking for an interpretation of Motor Vehicle Safety Standard No. 108 as it applies to a reflex reflector design that you attached. This design shows a single reflector 2 inches in height mounted behind a clear outer lens which is bisected horizontally by an opaque strip 6mm (.25 in.) wide, giving the impression from the exterior of two reflectors, one .75 in. high above the divider, and one that is 1.00 in. in height, below the divider. You have asked whether the "structure of the reflex reflector conforms to FMVSS 108," and whether photometric conformance is judged with respect to the single reflector crossed by the opaque strip, or whether both the upper and lower portions of the bisected reflector must meet the photometric specification. Standard No. 108 is a performance standard, not a design standard. The standard does not specify any requirements concerning the structure of reflectors. The applicable requirements for reflex reflectors are those of SAE Standard J594f Reflex Reflectors January 1977, which Standard No. 108 incorporates by reference. Your reflector should be tested as a single reflector according to the procedures set forth in J594f. If the reflector does not meet the photometric performance requirements of that standard, you may add sufficient reflective elements to the reflector design until conformance is achieved. There is no need to test the upper and lower portions as separate reflectors. If you have any further questions, you may refer them to Taylor Vinson (202) 366-5263 of this Office. Sincerely, John Womack Acting Chief Counsel ref:108 d:5/9/95
|
1995 |
ID: 0866Open Mr. Valter Sforca Dear Mr. Sforca: This is in reply to your letter of April 20, 1995, asking if there is a regulation that applies to the importation of an "air equalizer for tire pressure." Although you have not described your device, there are no Federal motor vehicle safety standards that apply to equipment installed in motor vehicles that regulate the air pressure of tires. If you are asked by the U.S. Customs Service to execute an HS-7 Declaration Form at the port of entry, you may check Box 1, declaring that the equipment was manufactured on a date when no applicable Federal motor vehicle safety standard was in effect. Because this device is motor vehicle equipment, and because you apparently would be its importer, you would be responsible for notifying buyers and recalling it if either you or we decided that it contained a safety related defect. We don't understand your phrase "the system have a safety valve for the air brakes the truck, for a properly stop". However, if the "air equalizer" is installed by a manufacturer, distributor, dealer, or motor vehicle repair business, that person must not knowingly make inoperative any part of a truck's air brake system by installing the air equalizer. I am enclosing a copy of a letter concerning what appears to be a similar device, which will explain this more fully. If you have any further questions, you may refer them to Taylor Vinson of this Office, with whom you spoke previously (202-366-5263). Sincerely,
John Womack Acting Chief Counsel Enclosure ref:591 d:5/4/95
|
1995 |
ID: 0869Open Mr. Scott E. Mack Dear Mr. Mack: This is in reply to your letter of April 24, 1995, requesting a confirmation of your interpretation that "Philips Color Clear (TM) Halogen Headlights . . . are in compliance with FMVSS-108." The product in questions "appears to be colored when not in use" but "when lighted it produces white light as defined by J579C." You have provided a report from ETL Testing Laboratories which "indicates that the color of the light is identical to that of a standard halogen headlight." There is no definition of white light in SAE J579c Sealed Beam Headlamp Units for Motor Vehicles, December 1978. We believe you mean SAE J578d Color Specification for Lighting Devices, September 1978 which does contain a definition expressed in chromaticity coordinates. The report you supplied indicates that the Philips lamp provides a light within the color coordinates for white when equipped with a red, black, blue, or white insert. As Standard No. 108 contains no requirements for the color of glass lamp lenses or bulbs, only the light emitted from the lamp, we confirm your conclusion that the Philips Color Clear (TM) headlamp has been designed to conform to the color requirements of Standard No. 108. We appreciated your visit to NHTSA on April 26 to demonstrate the lamp with its various inserts. I understand that the light produced by the lamp, and by a standard headlamp, appeared identical to the naked eye in a side by side comparison. If you have any further questions, you may refer them to Taylor Vinson of this Office (202-366-5263). Sincerely,
John Womack Acting Chief Counsel ref:108 d:5/11/95
|
1995 |
ID: 0880Open Mr. Donnell W. Morrison Dear Mr. Morrison: This is in reply to your letter of April 25, 1995, asking for a clarification of the letter of April 10 to you from the former Chief Counsel, Philip Recht. He explained Standard No. 108's requirements for the location of rear lighting on wide vehicles. As the letter stated, identification lamps are to be mounted "as close to the top of the vehicle as practicable." You speak of having seen "semitrailers on the highway with all the rear lights at bed level" including clearance and identification lamps. As the letter also stated, the determination of practicability is initially that of the manufacturer, to be made in its certification that the vehicle meets all applicable Federal motor vehicle safety standards. NHTSA will not question that determination unless it appears clearly erroneous. Without further information on the semitrailers you saw, we cannot judge whether mounting the clearance and identification lamps at bed level was a clearly erroneous determination by the trailer's manufacturer. There are some configurations where there is no header on which to mount lamps and the top of the doors approaches the top of the vehicle. In those configurations, we would not contest the manufacturer's determination that mounting the lamps at bed level was "as close to the top of the vehicle as practicable." On the other hand, the semitrailers you saw might have failed to conform to Standard No. 108. I hope that this clarifies the matter for you. If you have any further questions you may call Taylor Vinson of this Office (202-366-5263). Sincerely, John Womack Acting Chief Counsel Ref:108 d:5/19/95
|
1995 |
Request an Interpretation
You may email your request to Interpretations.NHTSA@dot.gov or send your request in hard copy to:
The Chief Counsel
National Highway Traffic Safety Administration, W41-326
U.S. Department of Transportation
1200 New Jersey Avenue SE
Washington, DC 20590
If you want to talk to someone at NHTSA about what a request for interpretation should include, call the Office of the Chief Counsel at 202-366-2992.
Please note that NHTSA’s response will be made available in this online database, and that the incoming interpretation request may also be made publicly available.