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 |
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ID: aiam3633OpenMr. Matt Guzzetta, Vice President, Don Vesco Products, Inc., 7565 North Avenue, Lemon Grove, CA 92045; Mr. Matt Guzzetta Vice President Don Vesco Products Inc. 7565 North Avenue Lemon Grove CA 92045; Dear Mr. Guzzetta: This is in reply to your letter of September 15, 1982, asking about th legality of 'covering of a headlamp on a motorcycle with a clear cover.'; You reported that manufacturers of motorcycles and fairings ar producing such covers. The National Highway Traffic Safety Administration views this practice as prohibited and will take appropriate steps to make its views known. The legal authority for this is based upon a requirement of the SAE incorporated by reference in Motor Vehicle Safety Standard No. 108 or, alternatively, paragraph S4.1.3 of that standard.; SAE Standard J580 (both a and b versions), *Sealed Beam Headlam Assembly*, is incorporated by reference in Tables I and III of Standard No. 108 as one of the standards pertaining to headlamps for use on passenger cars, trucks, buses, and multipurpose passenger vehicles. A paragraph in each version states that, 'When in use, a headlamp shall not have any styling ornament or other feature, such as a glass cover or grill, in front of the lens.' SAE J580a applies to all sealed beam headlamps, while the scope of J580b is considerably narrower, including only those not covered by SAE J579c.; The principal referenced SAE material for motorcycle headlamps is J584 *Motorcycle Headlamps*. As options, both J584 and S4.1.1.34 of Standard No. 108 allow, in effect, a motorcycle to be equipped with one half of any sealed beam system permissible on four-wheeled motor vehicles.; Paragraph S4.1.3 of Standard No. 108 forbids the installation o additional equipment 'that impairs the effectiveness of lighting equipment required' by Standard No. 108. Because of moisture accumulation, discoloration, cracks, etc., a glass or plastic cover might tend over a period of time to diminish or distort the headlamp beam. This is of particular concern with reference to the unsealed headlamps implicitly permitted by SAE J584 because of the tendency of the reflector to deteriorate with age.; For the reasons stated above, the agency has concluded that no headlam may have a glass or plastic shield in front of it when in use, regardless of the type of vehicle on which it is used.; As for the turn signals, no part of the vehicle may impair thei visibility through horizontal angles 45 degrees to the right and left of the vehicle (for right and left turn signals respectively) measured at the longitudinal axis of the vehicle. An unobstructed illuminated area of outer lens surface of at least 2 square inches excluding reflex is necessary to meet this requirement. You will have to judge for yourself whether the turn signal requirements are met with your planned cover in place.; If you have any further questions, we shall be happy to answer them. Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam4618OpenMr. Sadato Kadoya Manager, Safety Engineering Mazda (North America), Inc. Research & Development Center 1203 Woodbridge Avenue Ann Arbor, MI 48105; Mr. Sadato Kadoya Manager Safety Engineering Mazda (North America) Inc. Research & Development Center 1203 Woodbridge Avenue Ann Arbor MI 48105; "Dear Mr. Kadoya: This is to provide you with a clarification of ou letter to you dated November 3, l988, based upon your telephone conversation with Taylor Vinson of this Office. Our letter advised you that Standard No. l08 did not preclude the use of replaceable bulb headlamps with adjustable reflectors. In reply, you have cited two provisions of the standard which appear in conflict with this interpretation. With respect to a headlamp equipped with one or two HBl light sources, S4.1.1.36(e)(l) states that 'There shall be no mechanism that allows adjustment of an individual HBl or adjustment of reflector aim with two HBls .' To similar effect with respect to HB3 and HB4 light sources is S4.1.1.36(f)(l). Standard No. l08 has been amended effective June 8, l989, and the corresponding requirements are now S7.5(d)(l) and (e)(l). Each has been revised to state 'There shall be no mechanism that allows adjustment of an individual light source, or, if there are two light sources, independent adjustment of each reflector.' We believe that the revised wording of the new sections clearly allow the adjustment of single reflectors in single light source replaceable bulb headlamps, and dual reflectors in dual-light source replaceable bulb headlamps, provided that the reflectors are not capable of independent adjustment. Further, new S7.7.2.2 specifically addresses how moveable reflectors must operate. The intent of these sections is to prohibit headlamp designs in which the bulb alone is adjusted to aim the headlamp since this is contrary to mechanical aim requirements, or, where there is more than one reflector in a headlamp, designs in which each reflector may be adjusted independently, since this is also contrary to achieving precise mechanical aim. Thank you for bringing this matter to our attention. Sincerely, Stephen P. Wood Acting Chief Counsel /"; |
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ID: aiam3910OpenMr. Gordon Bonvallet, Manager, Photometric Division, ETL Testing Laboratories, Inc., P.O. Box 2040, Cortland, NY 13045- 2040; Mr. Gordon Bonvallet Manager Photometric Division ETL Testing Laboratories Inc. P.O. Box 2040 Cortland NY 13045- 2040; Dear Mr. Bonvallet: This is in reply to your letter of February 4, 1985, asking for a interpretation of the humidity testing procedure for replaceable bulb headlamps.; Paragraph S6.8 of Motor Vehicle Safety Standard No. 108 states i pertinent part that after completion of the test cycle in which the headlamp shall have been in an environment of 100 degrees Fahrenheit with a relative humidity of 90 *+* 10 percent, it shall then be in an environment with a temperature of 73 degrees Fahrenheit and relative humidity of 30 *+* 10 percent before removal for photometric testing. You believe that this implies an instantaneous transition in temperature/humidity conditions which, in your view, is 'impossible to achieve.' You have set forth three alternative procedures and ask which is the most acceptable to this agency.; Under your first alternative, the temperature and humidity in th humidity chamber would be reduced to 73 degrees Fahrenheit-43 percent, requiring about an hour, whereupon the headlamp would be removed to a 'dry box' chamber of the requisite temperature/humidity before photometric testing. In the second alternative, there would be no such removal before the photometric testing. In the third alternative, the headlamp would be removed from the humidity chamber and immediately carried to a 'dry box' with the requisite temperature/humidity, however, in your test set up this would require three to five minutes elapsed time between chambers.; Paragraph S6.8 does not specify a humidity of 43 percent in any of it test conditions, and a procedure incorporating the first and second alternatives clearly would not be in accordance with paragraph S6.8. That paragraph, however, does not specify that the temperature/humidity sequences must occur in the same chamber but it does imply that the lower temperature/humidity soak should take place directly following the higher temperature/humidity one. Therefore, your third alternative is the one that meets the intent of paragraph S6.8. To insure consistency of results, we recommend that no transfer period exceed three minutes and that the headlamp be exposed as briefly and as little as possible to the ambient temperature/humidity of the test laboratory.; Sincerely, Jeffrey R. Miller, Chief Counsel |
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ID: aiam4414OpenMr. M. Iwase, Manager, Technical Administration Dept., Koito Mfg., Co., Ltd., Shizuoka Works, 500, Kitawaki, Shimuzu-shi, Shizuoka-ken, JAPAN; Mr. M. Iwase Manager Technical Administration Dept. Koito Mfg. Co. Ltd. Shizuoka Works 500 Kitawaki Shimuzu-shi Shizuoka-ken JAPAN; Dear Mr. Iwase: This is in reply to your letter of September 15, 1987, with furthe reference to features of a 60 degree slant replaceable bulb headlamp presently being developed by Koito. You have explained that the aiming pads for the new system will be installed on the aiming adapter, rather than the headlamp lens, and have asked for confirmation that this is 'not illegal' under Motor Vehicle Safety Standard No. 108.; As you noted in your letter, paragraph S4.1.1.36(a)(2) specificall requires the exterior face of each replaceable bulb headlamp lens to have three aiming pads. The agency has no specifications for the design of aiming adapters, and a headlamp without aiming pads would be one that is not designed to conform to the standard.; The agency is examining concepts for aiming methods for other tha mechanical aim, but no amendments to Standard No. 108 are contemplated that would permit or require aiming pads to be on aiming adapters.; Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam5025OpenMr. Peter K. Brown President, KC HiLites, Inc. Avenida de Luces Williams, AZ 86046-0155; Mr. Peter K. Brown President KC HiLites Inc. Avenida de Luces Williams AZ 86046-0155; Dear Mr. Brown: This responds to your letter of May 6, 1992, wit respect to your 'quad beam' product. You point out that, in normal operation, the headlamp lower beam is extinguished when the upper beam is activated, 'quad beam' ensures that the lower beam remains activated when the upper beam is used. We advised you on July 2, 1990, that installation of 'quad beam' would be acceptable on certain types of four-lamp headlighting systems. You have now asked whether the device can 'legally be used on two headlamp systems, either sealed beam or replaceable bulb type?' Paragraph S5.5.9 of Federal Motor Vehicle Safety Standard No. 108 states that ' except for certain four-lamp systems enumerated in S5.5.8 the wiring harness or connector assembly of each headlamp system shall be designed so that only those light sources intended for meeting lower beam photometrics are energized when the beam selector switch is in the lower beam position, and that only those light sources intended for meeting upper beam photometrics are energized when the beam selector switch is in the upper beam position.' This would preclude installation of the 'quad beam' on two lamp headlamp systems. Sincerely, Paul Jackson Rice Chief Counsel; |
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ID: aiam5499OpenHerr Tilman Spingler Robert Bosch GmbH FAX 49-7121-35-1792; Herr Tilman Spingler Robert Bosch GmbH FAX 49-7121-35-1792; Dear Herr Spingler: We have received your FAX of February 15, 1995 asking whether a proposed design 'for a lens-reflector-joint can be considered as conforming to the appropriate definition in FMVSS 108.' The agency does not advise manufacturers whether particular designs are regarded as 'conforming.' That determination is to be made by the manufacturer in certifying that its product conforms to all applicable Federal Motor Vehicle Safety Standards. However, we can provide you with an interpretive guideline. Section S4 defines a 'replaceable bulb headlamp' as a headlamp 'comprising a bonded lens reflector assembly and one or two replaceable light sources.' The intent of the definition was that the lens and reflector assembly be an indivisible unit upon manufacture of the headlamp. This means that, if a lens is broken, the entire lens reflector assembly must be replaced. If your design is such that the lens cannot be removed from the reflector assembly for replacement, it would appear to meet the definition in S4. As you are well aware, NHTSA granted your company's petition for rulemaking, and, in November 1994, proposed an amendment of the definition of 'replaceable bulb headlamp' that would allow a replaceable lens if the headlamp incorporates a vehicle headlamp aiming device conforming to S7.8.5.2. Comments were due on this proposal February 21, 1995. In due course, after review of the comments, NHTSA will decide whether it will pursue further rulemaking or terminate the rulemaking action. Sincerely, Philip R. Recht Chief Counsel; |
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ID: aiam4703OpenMr. T. Chikada Manager, Automotive Engineering Lighting Control Dept. Stanley Electric Co. Ltd. 2-9-13, Nakameguro, Meguro-ku Tokyo 153, Japan; Mr. T. Chikada Manager Automotive Engineering Lighting Control Dept. Stanley Electric Co. Ltd. 2-9-13 Nakameguro Meguro-ku Tokyo 153 Japan; Dear Mr. Chikada: This is in reply to your letter of August 9, l989, t the former Chief Counsel, Erika Jones. You have asked for an interpretation of two of the amendments of May 9, 1989, to Federal Motor Vehicle Safety Standard No. 108. We have delayed answering you until action could be taken on petitions for reconsideration of the May 9 amendments. This action was taken on February 8, 1990 (copy of Federal Register notice enclosed), and the new amendments adopted then, effective March 12, l990, include definitions of 'Direct reading indicator' and 'Remote reading indicator.' Section S7.7.5.2(a)(l)(iii) states in pertinent part that each graduation on a Vehicle Headlamp Aiming Device (VHAD) 'shall indicate a linear movement of the scale indicator of not less than 0.05 in. (1.27 mm) if a direct reading analog indicator is used,' and 'if a remote reading indicator is provided, it shall represent the actual aim movement in a clear, understandable format.' Your letter depicts two devices identified as a 'direct reading analog indicator' and a 'remote reading indicator', and you ask for confirmation that each conforms with the requirements of the section. Preliminarily, we observe that your drawings do not depict how the devices are determined to be 'direct' and 'remote'. Our interpretation of your 'direct indicator' is that the location of the bubble is proportional to the slope of the surface and the adjustment, i.e., as the angle of aim changes, so does the location of the bubble, and its location relative to the graduations changes in proportion to the angle of aim. Our interpretation of your 'remote indicator' is that the location of the bubble represents the difference between the correct setting and the actual setting of the adjustment, and the reading may or mau not be proportional to the difference. Based on these interpretations, either device would appear to be capable of meeting the recently adopted definitions of direct and remote reading indicators. For example, if either device were mounted in its entirety on the headlamp to sense vertical attitude, the devices would both appear to be capable of directly reading the aim of the headlap and also appear to be capable of accommodating variations in floor slope. In this case, each device would meet the definition of a 'direct reading indicator'. And if either device were mounted in whole or in part elsewhere than on the headlamp or its aiming or mounting equipment (e.g., mounted on the firewall, inner fender panel, instrument panel), and linked mechanically to the headlamp such that its vertical aim was correctly displayed on the indicator, each device would also appear to meet the definition of a 'remote reading indicator'. Paragraph S7.7.2 requires in pertinent part that each headlamp aiming mechanism allow aim inspection and adjustment, and be accessible for such uses 'without removal of vehicle parts, except for protective covers removable without the use of tools.' You have asked whether the protective cover mentioned includes the cover to protect the spirit level when it is a component of the VHAD. The answer is no. The protective cover mentioned is one intended to shield the entire VHAD, or a cover that is not transparent and inhibits the proper aim inspection and adjustment. A transparent cover or transparent portions of a cover protecting the indicator (in your case, the spirit level of your direct reading indicator) is not required to be removable. However, if your remote reading indicator has a transparent protective cover, it would be required to be removable without the use of tools to gain access to the dial indicator, if the indicator is not adjustable with the cover in place. I hope that this answers your questions. Sincerely, Stephen P. Wood Acting Chief Counsel Enclosure; |
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ID: aiam1935OpenMr. Ernest D. Mathews, Chief, Field Services, Department of Motor Vehicles, Sate of Vermont, Montpelier, VT 05602; Mr. Ernest D. Mathews Chief Field Services Department of Motor Vehicles Sate of Vermont Montpelier VT 05602; Dear Mr. Mathews: This is in reply to your letter of April 17, 1975, to this agenc asking questions about paragraph S4.6(b) of Motor Vehicle Safety Standard No. 108, relating to headlamp flashers. Your reference to S4.5.8(b) is out-dated by approximately three years and I am enclosing a copy of Standard No. 108 as it now exists.; You asked the reason for the section in question, which provides tha 'All other lamps shall be steady- burning, except that means may be provided to flash headlamps and side marker lamps for signaling purposes.' You also asked whether all motor vehicles, including motorcycles, are 'authorized' by this section to use flashing headlamps, and finally whether the standard prohibits States from promulgating regulations to control flashing headlamps.; S4.6(b) was not intended as a regulation of this aspect of moto vehicle performance, in the sense that it would preempt all State regulation of the sale or use of headlamp flashers. It is basically merely an exception to the requirement of Standard 108 that all lamps (other than turn signals, hazard warning signals, and school bus warning signals) be steady-burning. The section, in other words, was included to make it clear that automatic headlamp flashers are not prohibited by the Federal standard. With reference to your questions, this is the only way in which they are 'authorized' by Standard 108.; We have concluded, therefore, that State regulation of headlam flashers is not preempted by the Federal standard.; Sincerely, James C. Schultz, Chief Counsel |
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ID: aiam2357OpenRoderick H. Willcox, Esq., Messrs. Chester, Hoffman, Park, Willcox, & Rose, 16 East Broad Street, Columbus, OH, 43215; Roderick H. Willcox Esq. Messrs. Chester Hoffman Park Willcox & Rose 16 East Broad Street Columbus OH 43215; >>> Re: W.B. Marvin Manufacturing Co.<<< Dear Mr. Willcox: This is in reply to your letter of June 16, 1976, asking severa questions with respect to the applicability of 15 USC 1397(a)(2)(A) of the National Traffic and Motor Vehicle Safety Act and Federal Motor Vehicle Safety Standard No. 108 (49 CFR 571.108) to a product manufactured by your client, the W.B. Marvin Manufacturing Company. This product is 'a screen which fits on the front part of the automobile and protects the radiator, headlamps and other lower parts of the car' from bugs.; W.B. Marvin would not be in violation of either the Act or Standard No 108 by manufacturing and selling these screens. Such liability as may exist centers on the installation of them. Standard No. 108 establishes requirements for lighting equipment on new motor vehicles, and for replacement equipment. One of the requirements of SAE Standard J580a, *Sealed Beam Headlamp*, June 1966, incorporated by reference in Standard No. 108, is that ' a headlamp, when in use, shall not have any styling or other feature, such as a glass cover or grille in front of the lens.' Since the screen is positioned in front of the headlamps it would be an 'other feature' of the type intended to be prohibited by the standard if, as appears likely, it affects compliance with headlamp photometrics (SAE Standard J579) or headlamp aim (SAE Standard J580). If installation results in a noncompliance, the screen could not, therefore, be legally installed by a vehicle manufacturer, distributor, or dealer as original equipment on a motor vehicle.; As for replacement equipment, under Section 1397 (a)(2)(A) of the Ac an automobile owner may himself modify his vehicle in any manner he chooses, but modifications performed at his request by others may not 'render inoperative in whole or part, any device or element of design installed on . . . a motor vehicle . . . in compliance with an applicable Federal motor vehicle safety standard.' If installation of the screen affects compliance with headlamp photometrics or other requirements, then it would appear to 'render inoperative' a lighting device installed in accordance with a Federal motor vehicle safety standard, within the meaning of Section 1397(a)(2)(A). Installation by the auto service center of the retailer would therefore be prohibited, since such a facility is deemed a 'motor vehicle repair business.'; There are no Federal motor vehicle safety standards that directly appl to the screen as an item of motor vehicle equipment, nor do I know of any other Federal regulation affecting it.; I hope this letter is responsive to your questions. Yours truly, Frank Berndt, Acting Chief Counsel |
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ID: aiam4683OpenTracey Powell Legislative Coordinator Government Relations American Motorcyclist Association P.O. Box 6114 Westerville, OH 43081-6114; Tracey Powell Legislative Coordinator Government Relations American Motorcyclist Association P.O. Box 6114 Westerville OH 43081-6114; Dear Tracey Powell: This is in reply to your letter of November l4 l989, with respect to existing prohibitions in some States against the use of modulating headlamps on motorcycles. The apparent basis of the prohibition is that flashing lamps are generally reserved for emergency vehicles. You point out the distinction that Standard No. 108 makes between the two types of headlamps, and ask our 'assistance in attaining uniform recognition of the legal use of modulating headlights through the United States . . . .' As you note, there is a legal distinction in Standard No. 108 between a modulating headlamp (one that goes from a higher to a lower intensity within either the upper or lower beam) and a flashing one (one that goes from either the upper or lower beam to off). Further, section S5.6.1 of Standard No. 108 provides that 'A headlamp on a motorcycle may be wired to modulate.' The authority of States to regulate this aspect of motorcycle lighting is constrained by section l03(d) of the National Traffic and Motor Vehicle Safety Act (l5 U.S.C. 1392(d)). This section provides in pertinent part that: w henever a Federal motor vehicle safety standard . . . is in effect, no State. . . shall have any authority either to extablish, or to continue in effect, with respect to any motor vehicle. . . any safety standard applicable to the same aspect of performance of such vehicle. . . which is not identical to the Federal standard.' The effect of this provision of the Safety Act with respect to lighting is to expressly prohibit a State from enacting a law that forbids a manufacturer from installing headlamp modulators on motorcycles. I hope that this responds to your concerns. Sincerely, Stephen P. Wood Acting Chief Counsel /; |
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.