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.”
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NHTSA's Interpretation Files Search
| Interpretations | Date |
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ID: 2414yOpen Ms Margaret Schmock Dear Ms Schmock: This is in reply to your FAX of March 6, l990, with respect to the relationship between Federal Motor Vehicle Safety Standard No. l08, and "CAC Title 13, Article 9". You have indicated that CAC requires a headlamp adjustment range in the horizontal of at least +/- 4 degrees, whereas Standard No. l08 requires a horizontal adjustment range of not less than 2.5 degrees. You have asked whether Bosch headlamps still must have an adjustment range of +/-4 degrees in the horizontal although Standard No. l08 has been changed. We understand that "CAC" refers to "California Administrative Code". The effect of the preemption provisions of the National Traffic and Motor Vehicle Safety Act is to prohibit California from adopting and enforcing a minimum horizontal headlamp adjustment range greater or less than 2.5 degrees. Thus, a State requirement that a headlamp have a horizontal range of +/- 4 degrees is invalid because it differs from a corresponding Federal requirement. We are unable to answer your further questions with respect to the California code, and suggest that, for further information you write Department of Motor Vehicles, State of California, 2415 First Avenue, Sacramento, California 95818, ATTN: Mr. A. A. Pierce, Director (FAX 916-732-7854). Sincerely, Stephen P. Wood Acting Chief Counsel ref:l08 d:4/25/90 |
1990 |
ID: nht90-2.25OpenTYPE: INTERPRETATION-NHTSA DATE: APRIL 25, 1990 FROM: STEPHEN P. WOOD -- ACTING CHIEF COUNSEL, NHTSA TO: MARGARET SCHMOCK -- ROBERT BOSCH GMBH TITLE: NONE ATTACHMT: TELEFAX DATED 6-3-90 TO STEPHEN P. WOOD FROM MARGRET SCHMOCK ATTACHED; (OCC 4508) TEXT: This is in reply to your FAX of March 6, 1990, with respect to the relationship between Federal Motor Vehicle Safety Standard No. 108, and "CAC Title 13, Article 9". You have indicated that CAC requires a headlamp adjustment range in the horizontal of at least +/- 4 degrees, whereas Standard No. 108 requires a horizontal adjustment range of not less than 2.5 degrees. You have asked whether Bosch headlamps still must have an adjustment range of +/-4 degrees in the horizontal although Standard No. 108 has been changed. We understand that "CAC" refers to "California Administrative Code". The effect of the preemption provisions of the National Traffic and Motor Vehicle Safety Act is to prohibit California from adopting and enforcing a minimum horizontal headlamp adjustm ent range greater or less than 2.5 degrees. Thus, a State requirement that a headlamp have a horizontal range of +/- 4 degrees is invalid because it differs from a corresponding Federal requirement. We are unable to answer your further questions with respect to the California code, and suggest that, for further information you write Department of Motor Vehicles, State of California, 2415 First Avenue, Sacramento, California 95818, ATTN: Mr. A. A. Pi erce, Director (FAX 916-732-7854). |
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ID: 24065.ztvOpen D.W. Robertson, Captain Dear Captain Robertson: This is in reply to your letter of January 28, 2002, to Taylor Vinson of this Office. You reported receiving inquiries regarding the legality of brush guards. You further reported that courts in Virginia differ on whether Section 46.2-1002 of the Code of Virginia applies to brush guards, and that "the question they have is, does the brush guards diminish the light output?" In your view, the brush guard raises three questions. We shall answer each in turn. "1. Are brush guards on motor vehicles, both front and rear, in compliance with FMVSS 108?" We would rephrase the question as whether motor vehicles equipped with front and rear brush guards are in compliance with Federal Motor Vehicle Safety Standard (FMVSS) No. 108. We addressed this issue in a letter of October 27, 1994, to Thomas L. Wright of the New Jersey Division of Motor Vehicles. I enclose a copy for your reference. In brief, paragraph S7.8.5 of FMVSS No. 108 prohibits new motor vehicles from being sold with "any styling ornament or other feature" in front of a headlamp lens; we regard a brush guard as an "other feature" of the type prohibited by S7.8.5. The letter notes that there is no similar direct prohibition in FMVSS No. 108 regarding other vehicle lamps, including front lamps, but that such other lamps must comply with the photometric requirements of FMVSS No. 108 with the brush guards in place. Thus, the installation of front brush guards in front of a lamp other than a headlamp, or rear brush guards, does not per se create a noncompliance with FMVSS No. 108. "2. Do brush guards impair the effectiveness of lighting equipment required by FMVSS 108?" Front brush guards in front of headlamp lenses are prohibited by S7.8.5. As the 1994 letter indicates, other front lamps and rear lamps must comply with photometric requirements with the brush guards in place, and compliance with FMVSS No. 108 would depend on the design and location of the specific brush guard. Compliance also requires that rear lamps meet visibility requirements at certain angles to the right and left of the vehicle. "3. Are brush guards allowed to be installed on new vehicles by manufacturers?" If not, why?" A manufacturer must certify that the vehicles it manufactures comply with all applicable Federal motor vehicle safety standards. Thus, a manufacturer could not certify compliance with FMVSS No. 108 if a vehicle is equipped with brush guards in front of headlamp lenses as prohibited by S7.8.5. The manufacturer could certify compliance with FMVSS No. 108 if brush guards are in front of lamps other than headlamps and if it determines that those lamps meet all applicable photometric and visibility requirements with the brush guards installed. FMVSS No. 108 is not the only Federal motor vehicle safety standard for which compliance may be affected by installation of front brush guards. I enclose a copy of our letter of July 3, 1997, to Steve Brookmire, discussing the relationship of brush guards to airbag deployment under FMVSS No. 208. Sincerely, Jacqueline Glassman Enclosures |
2002 |
ID: nht89-1.92OpenTYPE: INTERPRETATION-NHTSA DATE: 05/22/89 FROM: H. HASEGAWA -- AUTOMOTIVE LIGHTING ENGINEERING CONTROL SECT. STANLEY ELECTRIC CO LTD TO: RICHARD L. VAN IDERSTINE -- SAFETY STANDARDS ENGINEER U.S. DOT, NHTSA OFFICE OF VEHICLE SAFETY STANDARDS TITLE: REVISION OF FMVSS NO. 108 (DOCKET NO. 85-15 NOTICE 8) ATTACHMT: ATTACHED TO LETTER DATED 06/19/89 FROM STEPHEN P. WOOD -- NHTSA TO HASEGAWA; REDBOOK A33 [3]; STANDARD 108; DOCKET 85-15 NOTICE 8 TEXT: Dear Mr. Van Iderstine, We appreciate very much for your kind cooperation during our stay in the U.S. for SAE Lighting Commity Meeting. We have two questions on Revision of FMVSS No. 108 (Docket No. 85-15 Notice 8) which was finally issued on Federal Register of May 9, 1989. - Question - 1. Please advice us the effective date of the requirement of S7.7.5.1 a). We suppose that S7.7.5.1 will be applied to the all headlamp with external aiming system (including replaceable bulb type headlamp). However, this requirement was not applied for replaceable bulb type headlamp by previous FMVSS No. 108. Therefore, we think that addition of new requirement need longer interval of effectiveness. 2. The requirement of S7.7.5.1 b) used quote SAE J580b "Sealed Beam Headlamp Assembly" by previous FMVSS No. 108 and the expression is little bit different from new S7.7.5.1 b). Please advice us that the requirement of "0.1 in. max." will be determined, either during the test or after the test? We would like to have your advice by facsimile. Our facsimile number is 03-792-0007 (JAPAN). Sincerely yours, |
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ID: Yuen.1OpenMr. Derek Yuen Dear Mr. Yuen: This responds to your recent e-mail to the National Highway Traffic Safety Administration (NHTSA), in which you seek clarification regarding the requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment, pertaining to motorcycle headlamps. Specifically, you asked whether a motorcycle (or a three-wheeled vehicle with two wheels at the front) may be equipped with a four-headlamp system (with two lower beams and two upper beams), and if so, whether it would be permissible to place one set of lamps (either the lower beams or upper beams) closer to the outer edge of the vehicle, provided that the other two lamps are within 200 mm of each other. As discussed below, FMVSS No. 108 does not permit a motorcycle headlamp system composed of more than two headlamps, so we need not consider the additional issue of spacing of a second pair of headlamps. By way of background, NHTSA is authorized to issue Federal motor vehicle safety standards that set performance requirements for new motor vehicles and items of motor vehicle equipment. As an initial matter, you are correct in that the three-wheeled vehicle mentioned in your letter would be considered a "motorcycle" under our regulations. Under 49 CFR 571.3, "motorcycle" is defined as "a motor vehicle with motive power having a seat or saddle for the use of the rider and designed to travel on not more than three wheels in contract with the ground". The requirements for motor vehicle lighting are contained in FMVSS No. 108, with the headlighting requirements for motorcycles set forth in S7.9, Motorcycles. In particular, paragraph S7.9.6 requires that a headlighting system be located on the front of the motorcycle and, most pertinent to your proposed design, be installed in accordance with the requirements of S7.9.6.2. The requirements of S7.9.6.2 are as follows: (a) If the system consists of a single headlamp, it shall be mounted on the vertical centerline of the motorcycle. (b) If the system consists of two headlamps, each of which provides both an upper and lower beam, the headlamps shall be mounted either at the same height and symmetrically disposed about the vertical centerline or mounted on the vertical centerline. (c) If the system consists of two headlamps, one of which provides an upper beam and one of which provides the lower beam, the headlamps shall be located on the vertical centerline with the upper beam no higher than the lower beam, or horizontally disposed about the vertical centerline and mounted at the same height. Because the system your letter envisions consists of four headlamps, it would not meet the requirements of S7.9.6.2 of FMVSS No. 108. (We note further that the Japan Auto Parts Industries Association submitted a petition for rulemaking in 1998, which included a request to amend FMVSS No. 108 to allow four distinct headlamps on motorcycles, but the agency decided not to do so (see 69 FR 55993 (Sept. 17, 2004). ) Because such a system is not permitted under Standard No. 108, we need not analyze this system in terms of the motorcycle headlamp location requirements contained in paragraph S7.9.6 of the standard. If you have further questions, please feel free to contact Eric Stas of my staff at this address or by telephone at (202) 366-2992. Sincerely, Stephen P. Wood Enclosure |
2006 |
ID: nht89-2.5OpenTYPE: INTERPRETATION-NHTSA DATE: 06/16/89 FROM: TAKAYOSHI CHIKADA -- MANAGER OF AUTOMOTIVE LIGHTING ENGINEERING CONTROL DEPT. STANLEY ELECTRIC TO: RICHARD L. VAN IDERSTINE -- SAFETY STANDARDS ENGINEER TITLE: REVISION OF FMVSS NO.108 (DOCKET NO.85-15 NOTICE 8) ATTACHMT: ATTACHED TO LETTER 08/23/89 FROM STEPHEN P. WOOD -- NHTSA TO TAKAYOSHI CHIKADA; REDBOOK A34[3]; STANDARD 108 TEXT: Dear Mr. Van Iderstine, We thank you very much for your kind cooperation during our stay in the U.S. for SAE Lighting Committee Meeting. We would like have your advice concerning interpretation of new FMVSS No. 108 (Docket No.85-15 Notice 8). 1. The requirement of S7.7.5.1.a) was not applied to replaceable type headlamp by previous FMVSS No.108. Please give us your advice whether this requirement will also be applied to the replaceable bulb type headlamps which are already manufactured accor ding to the previous FMVSS No.108. 2. The requirement of S7.7.5.1.b) need to quote SAE J580 b "Sealed Beam Headlamp Assembly" by previous FMVSS No. 108 and the expression seem to be slightly different from new S7.7.5.1.b). Please advice us whether the requirement of "0.1 in. max." is cond itioned when headlamp is being pushed or after said force is removed. 3. How should we prove the confirmation to the requirement of S7.7.2.2? We think the combinations of Horizontal and Vertical angle within the aim range will be so huge and it is not practicable to test for all combinations. 4. It is acceptable to set up initial "0" point of S7.7.5.2.a).2) not mechanically but photometrically? Please give us your advice by return facsimile. We thank you very much in advance. Yours faithfully,
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ID: 2111yOpen AIR MAIL Mr. S. Watanabe, Manager Automotive Lighting Engineering Control Dept. Stanley Electric Co., Ltd. 2-9-l3, Nakameguro, Meguro-Ku Tokyo l53, Japan Japan FAX 03-792-00007 Dear Mr. Watanabe: This is in reply to your FAX of September 14, l989, asking for an interpretation of Motor Vehicle Safety Standard No. l08, with respect to a vehicle headlamp aiming device (VHAD), as shown in the drawing attached to your letter. You have two questions: "1) Does a VHAD without a function which compensates the deviation of floor slope satisfy FMVSS No. l08 S7.7.5.2(a)(l(v)?" Paragraph S7.7.5.2(a)(v) states that "Means shall be provided in the VHAD for compensating for deviations in floor slope not less than 1.2 degrees from the horizontal that would affect the correct positioning of the headlamp for vertical aim." If a VHAD is "without a function which compensates the deviation of floor slope" it would not satisfy Standard No. l08. "2) This Head Lamp is designed to be aimed vertically by means of observing only one spirit level placed on the movable reflector, as shown in the drawing. Does this structure of VHAD satisfy FMVSS No. l08 S7.7.5.2(a)(l)(v)?" The answer is yes, if observation of the simple spirit level is coordinated with an off-vehicle measurement of floor slope. As located, the spirit level with the range of +/- 1.2 degree range will allow aim of the headlamp, even though the vehicle may not be level, and will compensate for floor slopes of up to 1.2 degrees, thus fulfilling the requirement that there be compensatory means when the vehicle upon which the headlamp is mounted is not resting upon level ground. I hope that this answers your questions. Sincerely, Stephen P. Wood Acting Chief Counsel ref:l08 d:ll/6/89 |
1970 |
ID: 7023Open Mr. James G. White FAX: 613-998-1965 Dear Mr. White: This responds to your FAX of February 18, 1992, to Richard Van Iderstine of this agency, who has asked this office to respond to your question 1.a. That question is: "Is Koito correct in stating that FMVSS 108 does not require the 'O' point on IHAD (sic) indicators to be marked by the numeral '0'"? In the letter from Koito that you furnished, Koito had remarked that the requirement in S7.7.5.2(a)(1) and (2) of Standard No. 108 "to have a zero mark" did "not necessarily mean a mark of figure 'O', but may be just a reference mark." Koito is incorrect. S7.7.5.2 On-vehicle aiming specifies requirements for Vehicle Headlamp Aiming Devices (VHADs). VHADs provide for headlamp aim inspection in both the vertical and horizontal axes. S7.7.5.2(a)(2) Horizontal aim states that "An 'O' mark shall be used to indicate alignment of the headlamps relative to the longitudinal axis of the vehicle." This clearly establishes the requirement for use of the figure "0" as the mark, and not use of a reference mark. You will note that S7.7.5.2(b) references setting the VHAD "at 'O' vertical and 'O' horizontal." This means at the "O" mark. Both S7.7.5.2(a)(1) Vertical aim and (a)(2) reference the necessity to provide "an equal number of graduations from the 'O' position representing angular changes in the axis." These graduations are not required to be marked. The presence of the "O" mark will assist the person aiming the headlamp to ensure that the VHAD is set at the junction of the horizontal and vertical axes, rather than at one of adjacent, unmarked graduations. Sincerely, Paul Jackson Rice Chief Counsel ref:109 d:3/5/92 |
1992 |
ID: nht92-8.32OpenDATE: March 5, 1992 FROM: Paul Jackson Rice -- Chief Counsel, NHTSA TO: James G. White -- Head, Crash Avoidance Standards (ASFBE), Road Safety and Motor Vehicle Regulation, Transport Canada TITLE: None ATTACHMT: Attached to letter dated 1/29/92 from J. Yoshimoto to James G. White TEXT: This responds to your FAX of February 18, 1992, to Richard van Iderstine of this agency, who has asked this office to respond to your question 1.a. That question is: "Is Koito correct in stating that FMVSS 108 does not require the 'O' point on IHAD (sic) indicators to be marked by the numeral 'O"'? In the letter from Koito that you furnished, Koito had remarked that the requirement in S7.7.5.2(a) (1) and (2) of Standard No. 108 "to have a zero mark" did "not necessarily mean a mark of figure 'O', but may be just a reference mark." Koito is incorrect. S7.7.5.2 On-vehicle aiming specifies requirements for Vehicle Headlamp Aiming Devices (VHADs). VHADs provide for headlamp aim inspection in both the vertical and horizontal axes. S7.7.5.2(a)(2) Horizontal aim states that "An 'O' mark shall be used to indicate alignment of the headlamps relative to the longitudinal axis of the vehicle." This clearly establishes the requirement for use of the figure "O" as the mark, and not use of a reference mark. You will note that S7.7.5.2(b) references setting the VHAD "at 'O' vertical and 'O' horizontal." This means at the "O" mark. Both S7.7.5.2(a)(1) Vertical aim and (a)(2) reference the necessity to provide "an equal number of graduations from the 'O' position representing angular changes in the axis." These graduations are not required to be marked. The presence of the "O" mark will assist the person aiming the headlamp to ensure that the VHAD is set at the junction of the horizontal and vertical axes, rather than at one of adjacent, unmarked graduations. |
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ID: Mills.1OpenRobert G. Mills, Supervisor, Homologation Dear Mr. Mills: This responds to your March 22, 2005, letter in which you requested clarification regarding the proper method for measuring the required edge-to-edge separation distance between a motorcycles front turn signal lamps and headlamp under Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment. Specifically, your letter asked whether the minimum edge-to-edge separation distance is measured: (1) "In a 2-dimensional plane, viewed directly from the front of the motorcycle, that would only take account of the visible, vertical edge-to-edge distance between the two lamps" or (2) "In a tangential plane that would take account of the upward/downward or forward/rearward separation distance". As discussed below, our interpretation differs from the two you suggest. We interpret Standard No. 108s requirement for the separation distance between a motorcycles front turn signal lamps and headlamp as being the shortest distance between the edges of each lamps effective light-emitting surface as projected onto a two-dimensional vertical plane perpendicular to the longitudinal axis of the motorcycle (i.e. , the view that would be perceived by oncoming drivers). This projection is defined within FMVSS No. 108 as the "effective projected luminous lens area". By way of background, Table IV, Location of Required Equipment, of FMVSS No. 108 requires motorcycle front turn signal lamps to have a minimum edge-to-edge separation distance of four inches between these lamps and the headlamp. Our interpretation that the distance is measured with a two-dimensional frame of reference is consistent with both the purpose of the standards separation requirement and at least one prior interpretation. Standard No. 108 specifies a minimum separation distance between headlamps and turn signal lamps to minimize the possibility that an observer will not see the turn signal. A motorist approaching the motorcycle in oncoming traffic will perceive the required four-inch edge-to-edge separation distance in a two-dimensional plane. If measurement along a tangential plane were substituted, as in the second method identified in your letter, the perceived separation distance in this scenario may be reduced to less than four inches, as seen by the driver, and a situation could arise in which the conspicuity of the turn signal is masked by the headlamp beam. If the oncoming driver does not perceive the important information provided by the turn signal, traffic safety could be compromised. The minimum edge-to-edge separation distance is the shortest distance between the edges of the effective projected luminous lens areas of the two lamps. "Effective projected luminous lens area" is defined in S3 of FMVSS No. 108 as "the area of the orthogonal projection of the effective light-emitting surface of a lamp on a plane perpendicular to a defined direction relative to the axis of reference". In this case, the defined direction is the longitudinal axis of the motorcycle. This same reasoning and result were applied in our interpretation letter of April 23, 1986 to a party whose identity was kept confidential (see enclosure). That letter dealt with the plane of reference for measuring the separation distance between a motorcycles rear turn signals and stop/tail lamp and the view provided to traffic approaching from the rear. However, the principles and reasoning are otherwise identical to the forward-facing situation. We would also point out an important additional requirement for motorcycle turn signal lamp placement contained in Table IV. That requirement is that the turn signal lamps must not be closer than 16 inches, as measured from their centers. If you have further questions, please feel free to contact Eric Stas of my staff at this address or by telephone at (202) 366-2992. Sincerely, Jacqueline Glassman Enclosure |
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.