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: nht69-1.46OpenDATE: 09/10/69 FROM: AUTHOR UNAVAILABLE; C. A. Baker; NHTSA TO: Blue Bird Body Company TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of August 8, 1969, concerning the operation of red warning lamps on school buses. Paragraph S3.1.3.2 (b)(2) of Federal Motor Vehicle Safety Standard No. 108 appears to require that the red warning lamps be e-nergized when a school bus door is opened for any purpose. However the intent of the standard is that the red warning lamps be energized only when the bus entrance door is open for the admission or discharge of passengers (i.e. that the red lamps be activated automatically only after manual energization of the amber lamps), and many manufacturers have, in our view, correctly go interpreted S3.1.3.2 (b)(2). |
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ID: nht68-2.14OpenDATE: 07/03/68 FROM: AUTHOR UNAVAILABLE; David A. Fay; NHTSA TO: Ideal Manufacturing Company TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of June 10, 1968, to Mr. J. O'Gorman of this Bureau, concerning the requirements for side reflex reflectors as specified in Federal Motor Vehicle Safety Standard No. 108. As noted in your letter, paragraph S3.1.1.6 of Standard No. 108, effective January 1, 1969, permits until January 1, 1970, the use of two side reflex reflectors on each side of vehicles that are less than 80 inches in overall width. On and after January 1, 1970, Standard No. 108 requires that these vehicles be equipped on each side with two side reflex reflectors and two side marker lamps. Thank you for writing. |
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ID: nht68-2.34OpenDATE: 10/18/68 FROM: AUTHOR UNAVAILABLE; Robert M. O'Mahoney; NHTSA TO: Citroen Cars Corporation TITLE: FMVSS INTERPRETATION TEXT: By your letter of October 8, 1968 you ask if the glazing material in the rear window of passenger cars can be 4 millimeters thick and be in compliance with Federal Motor Vehicle Standard No. 205; Glazing Materials - Passenger Cars, Multipurpose Passenger Vehicles, Motorcycles, Trucks, and Buses. Standard No. 205 requires that glazing materials conform to the ASA Standard Z26.1-1966. The ASA standard Z26.1-1966 does not set forth how thick glazing material must be but requires the glass used to meet certain tests, depending on the type of vehicle the glass is being used in and the location of the glass in that vehicle. |
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ID: nht68-3.1OpenDATE: 05/17/68 FROM: AUTHOR UNAVAILABLE; David A. Fay; NHTSA TO: Berliner Motor Corporation TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of April 10, 1968, addressed to Mr. William H. Risteen, concerning the requirement for headlamp dimmer switches as specified in Federal Motor Vehicle Safety Standard No. 108. Paragraph S3.4.1 of Standard No. 108 requires that a means for switching between lower and upper headlamp beams shall be provided in accordance with SAE Recommended Practice J564a or J565a. This general requirement is applicable to all vehicles, including motocycles, that are required, by Standard No. 106, to be equipped with lower and upper bean headlamps, even though SAE Recommended Practice J564a is addressed only to passenger cars. Thank you for writing. |
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ID: nht68-3.11OpenDATE: 01/26/68 FROM: AUTHOR UNAVAILABLE; Roger H. Compton; NHTSA TO: Truck-Lite Company TITLE: FMVSS INTERPRETATION TEXT: In your letter of December 6, 1967, you requested our comments on the applicability of SAE Standard J567, as sub-referenced in Motor Vehicle Safety Standard No. 108. As mentioned in your letter, the intent of the reference to SAE J567 is to ensure that replacement bulbs are compatible with the standard bulb sockets. Therefore, any sealed, disposable type, bulb-lens unit, in which the bulb is not a replaceable component, need not comply with the requirements of SAE Standard J567. This provision in no way exempts these sealed units from the other requirements of Motor Vehicle Safety Standard No. 108. |
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ID: nht68-3.23OpenDATE: 04/16/68 FROM: AUTHOR UNAVAILABLE; David A. Fay; NHTSA TO: Bayerische Motoren Werke TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of February 21, 1968, to Mr. J. E. Leysath of this Bureau, concerning the use of tubular type bulbs in license plate lamps. Motor Vehicle Safety Standard No. 108 requires that license plate lamps conform to Society of Automotive Engineers (SAE) Standard J587b. SAE J587b in turn requires that bulbs and bulb sockets conform to SAE Standards J573b and J567b, respectively. Since tubular type bulbs and sockets for these bulbs do not conform to these SAE Standards, their use in license plate lamps would not be permitted under the requirements of Standard No. 108. Thank you for writing. |
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ID: nht68-3.26OpenDATE: 04/24/68 FROM: AUTHOR UNAVAILABLE; G. C. Nield; NHTSA TO: The Standard-Triumph Motor Company, Limited TITLE: FMVSS INTERPRETATION TEXT: This letter is in response to your February 29, 1968, request for approval of equivalent rims for use in the following tire and rim combinations: A. Bias Ply Tires 1. 5.20-13 on 4 1/2J rim. 2. 5.60-13 on 3 1/2J rim. B. Radial Ply Tires 1. 145-13 on 3 1/2J rim. 2. 145-13 on 4 1/2J rim. 3. 185-15 on 4 1/2J rim. On the basis of the supporting information submitted, your request for approval of the equivalent rims and proposed tire combinations listed above is granted. |
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ID: nht68-4.21OpenDATE: 11/18/68 FROM: AUTHOR UNAVAILABLE; R. Brenner for William Haddon, Jr., M.D.; NHTSA TO: General Motors Corporation TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of September 25, 1968, regarding Federal Motor Vehicle Safety Standard No. 211 and the use of hexagonal wheel nuts. The requirement of this standard that wheel nuts, hub caps and wheel dirce "shall not incorporate vinged projections" apparently applied to all wheel nuts, whether hexagonal or otherwise. I agree that clarification of the standard is needed, but the method of accomplishing this is yet to be resolved. I have asked the Motor Vehicle Safety Performance Service to look into this problem immediately and to take the neccessary steps to relieve any undue burdens. |
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ID: nht71-3.15OpenDATE: 06/08/71 FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA TO: Mercedes-Benz of North America, Inc. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your May 21, 1971, letter to Mr. H. H. Wallace to determine whether Dunlop is in compliance as to the use of spaces in the tire identification number. There are no objections to the spaces between the different parts of the number. However, the photograph illustrates other problem, that of a dual size marked tire. Dual size marked tires are not permissible. The tire can be labeled as one size tire with the indication that it replaces another size tire. For example, 205R14 replaces ER70-14. The General Secretary of ETRTO has been advised of the "dual marked" tire usage. |
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ID: nht72-2.27OpenDATE: 06/05/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: State of Louisiana TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of May 26 to Mr. Schneider, referencing your conversation with Mr. Vinson of this office on Federal motor vehicle safety standards appliable to mobile homes. In answer to your questions: (1) Mobile homes (house trailers) are required to comply with the same Federal Safety Standards applicable to other types of trailers. (2) Lights are not required to be permanently installed. The use of a temporary lighting harness, removable when the home was completed its trip from factory to point of purchase, is acceptable. (3) There are no Federal safety standards for hydraulic surge brakes on trailers. |
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.