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: nht74-3.1OpenDATE: 07/30/74 FROM: RICHARD B. DYSON -- NHTSA ACTING CHIEF COUNSEL TO: P. K. KAMATH -- SENIOR SAFETY ENGINEER OSHKOSH TRUCK CORPORATION TITLE: N40-30 [ZTV] ATTACHMT: LETTER DATED 07/09/74 FROM P.K. KAMATH TO RICHARD DYSON -- NHTSA, 49CFR PART 571 FMVSS 101; CONTROL LOCATION, IDENTIFICATION AND ILLUMINATION TEXT: Dear Mr. Kamath: This is in reply to your letter of July 9, 1974, asking whether Standard No. 101 requires identification and illumination of an emergency engine stop control, in addition to the engine stop control intended for normal use. The "engine stop" control referred to in Standard No. 101 means any control used to stop the engine, and would include the emergency control. If it is important for the normal control to be identified and illuminated, it is all the more important that a control intended for emergency use meet the requirements of the standard. Identification such as "emergency engine stop" would be acceptable under Standard No. 101. Illumination, of course, must meet the requirements of the standard, but since you have not described the emergency system or its location we cannot offer a more precise comment. Yours truly, |
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ID: nht74-3.13OpenDATE: 01/03/74 FROM: AUTHOR UNAVAILABLE; Lawrence R. Schneider; NHTSA TO: General Motors Corporation TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of December 3, 1973, requesting clarification of paragraph S5.1(c) of Motor Vehicle Safety Standard No. 217, "Bus Window Retention and Release." Your letter, and attached photograph of a push-out window, suggest that the words "window frame" in S5.1(c) refer not to the window "sash", the structure immediately surrounding the glazing material, but to the side of the bus. We do not agree. The words "window frame" in S5.1(c), with respect to the push-out window, refer to the component that interfaces with the glazing. The intent of S5.1 is to require a window retention system to be strong enough to retain occupants in a crash, at least up to the strength limit of the glazing itself. Since there are no limits on movement of the window "sash" relative to the bus structure, the interpretation you suggest would allow a window system that provides no retentive properties at all, thus defeating one of the main purposes of the standard. |
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ID: nht73-1.50OpenDATE: 08/20/73 FROM: Richard B. Dyson; NHTSA TO: Takata Kojyo Company, Ltd. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of July 31, 1973, concerning the meaning of the term "75 percent extension" as used in S5.2(j) of Motor Vehicle Safety Standard No. 209. The 75 percent extension point used in 85.2(j) is intended to represent the belt's extension during its use in a vehicle. The measurement of extension is therefore begun with the webbing retracted as fully as the design of hardware and the size of the retractor permit. It may be that when the belt is retracted to this point a considerable amount of webbing remains outside the retractor, as shown in Figure 2 of your letter. The measurement of extension nonetheless begins at this point, so that "75 percent extension" is 75 percent of the incremental webbing length between this point and the point of fullest extension. To refer to the figures accompanying your letter, the measurement technique shown in Figure 2 is correct. That shown in Figure 1, which is based on 75 percent of the total length of the belt, is incorrect. |
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ID: nht73-2.27OpenDATE: 04/04/73 FROM: RICHARD B. DYSON -- NHTSA ASSISTANT CHIEF COUNSEL TO: PAUL K. WILSON -- TRUCK TRAILER MANUFACTURERS ASSOCIATION TITLE: NONE ATTACHMT: ATTACHED TO LETTER DATED 03/10/81, FROM FRANK BERNDT -- NHTSA TO DONALD W. VIERIMAA, NOA 30, REDBOOK A22, STANDARD 108; LETTER DATED 02/09/81 FROM DONALD W. VIERIMAA TO FRANK BERNDT -- NHTSA, EXCLUSION OF THE TOWBAR OF A PERMANENT TRAILER DOLLY FROM THE FMVSS 108 LENGTH CRITERIA TEXT: Dear Mr. Wilson: This is in reply to your letter of March 19, 1973, asking whether a towbar dolly must be included in determining the overall length of semitrailers for compliance with Federal Motor Vehicle Safety Standard No. 108. The answer is no. Standard No. 108 is a manufacturing standard, and semitrailers are not manufactured with dollies attached. 49 CFR S390.7, to which you refer, is a definition of the Bureau of Motor Carrier Safety which regulates the operation of certain motor vehicles, and since trailers often use converter dollies, it is understandable that that agency would deem a trailer with a dolly a "full trailer." Yours truly, [DIAGRAMS OMITTED] |
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ID: nht73-2.39OpenDATE: 03/26/73 FROM: E. T. DRIVER -- DIR., OFFICE OF OPERATING SYSTEMS, MVP; SIGNATURE BY CHARLES A. BAKER TO: Monsanto Textiles Company TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of March 12, 1973, requesting assignment of a tire manufacturer's identification code number to Monsanto Company. In a telephone conversation March 12, 1973, your Mr. E. Schary explained to our Mr. F. Koch that you are building experimental and development tires for test on vehicles that remain under your control. It is understood that the tires are not sold or leased to the general public. Under these conditions you are required to have a tire identification code number. These tires must, however, conform to Standard No. 109, and be certified as such by applying the DOT symbol to the sidewall. We understand you are acquainted with these requirements. To bring you up to date with recent progress in development of new and amended regulations we are enclosing several of the latest(Illegible Word) pertaining to rule making. Please let us know if you have any other questions regarding the applicability of the tire identification code and whether we can be of further assistance. |
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ID: nht73-3.20OpenDATE: 02/07/73 FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA TO: Michael J. Long TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of January 30, 1973, concerning acrylic headlamp covers. Federal Motor Vehicle Safety Standard No. 108 Incorporates Society of Automotive Engineers (SAE) Standard J580a, which prohibits the use of acrylic headlamp covers as original equipment. The requirements of SAE Standard J580a have also been incorporated in a number of State regulations, which are applicable to vehicles in use. Copies of Standard No. 108 and SAE Standard J580a are enclosed for your information. A Notice of Proposed Rule Making (Docket 69-19; Notice 3) on Standard No. 108 was issued on October 16, 1972. This Notice includes a provision for optional use of headlamp covers which conform to certain performance requirements. Such requirements are specified in paragraph S7.9 of the Notice (copy enclosed). Acrylic Industries Pty. Ltd. may be interested in commenting on this proposed revision of Standard No. 108. The closing date for comments is April 18, 1973. If you have any questions on the enclosed documents, please do not hesitate to contact me. |
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ID: nht75-1.2OpenDATE: 02/24/75 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Volkswagen of America, Inc. TITLE: FMVSS INTERPRETATION TEXT: N40-30 (TH) FEB 24 1975 Mr. J. W. Kennebeck Volkswagen of America, Inc. Englewood Cliffs, New Jersey 07632 Dear Mr. Kennebeck: This responds to Volkswagen of America's January 24, 1975, request for written confirmation that S5.3.3 of Standard No. 105-75, Hydraulic brake systems, only requires indication of a low fluid level condition (S5.3.1(b)) with the vehicle on a level surface, but that, in the event of a decrease in this fluid level (and apparent fluid volume) due to positioning the vehicle on an incline, the indicator lamp is permitted to activate and then deactivate when the vehicle is repositioned on a level surface. Your understanding of the requirements of S5.3.3. for indication of a low fluid level condition (S5.3.1(b)) is correct. S5.3.3 requires low fluid level indication with the vehicle on a level surface, and an activation due only to positioning on an incline may be extinguished when the vehicle is again placed on a level surface. Yours truly, Richard B. Dyson Assistant Chief Counsel |
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ID: nht75-2.21OpenDATE: 10/03/75 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: High & Walters TITLE: FMVSS INTERPRETATION TEXT: This is in response to your August 11, 1975, request for information on regulations concerning the matching of innertube sizes with motorcycle tire sizes. Federal Motor Vehicle Safety Standard No. 119 (copy enclosed) specifies performance and labeling requirements for motorcycle tires manufactured after March 1, 1975. There are no Federal regulations, however, containing requirements for proper matching of tubes with tires. Yours truly, Enclosure HIGH & WALTERS -- ATTORNEYS AT LAW August 11, 1975 Department of Transportation 400 - 7th Street SW Washington, D.C. 20590 TIPE SAFETY REGULATIONS Madam or Sir, would you please inform this office how we might obtain any regulations of the Department of Transportation relating to proper tube sizes for particular tire sizes. We are interested specifically in motorcycle tire regulations with regard to the size of the innertube for a given tire size. Thank you in advance for your assistance with regard to this matter. JAMES P. WALTERS |
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ID: nht75-2.3OpenDATE: 10/28/75 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Swan and Woodford TITLE: FMVSS INTERPRETATION TEXT: This responds to your August 27, 1975, request for standards applicable to glass-belted tires with the size designation H78-15 which were standard equipment on a 1973 Ford automobile. Such tires are subject to Federal Motor Vehicle Safety Standard No. 109, New Pneumatic Tires -- Passenger Cars, a copy of which is enclosed. YOURS TRULY, SWAN & WOODFORD August 27, 1975 National Highway Traffic Safety Administration Re: Standards for Firestone Brand Tires This letter is to inquire of any available information regarding standards for the below listed equipment. Size H-78-15 glass-belted Firestone brand tires; standard equipment on 1973 Ford automobile. I am particularly interested in a standard as it applies to "blow outs" at 65 miles per hour on an improved road with tires having been driven 14,000 miles. ("Blow-out" occurred in inner sidewall Thanking you in advance for your cooperation. C. BRAD WOODFORD |
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ID: nht75-4.2OpenDATE: 05/28/75 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Trailmaster Tanks, Inc. TITLE: FMVSS INTERPRETATION TEXT: This responds to Trailmaster Tank's May 14, 1975, request for a discussion of what constitutes the manufacture of a trailer in cases where used components from an existing vehicle are involved. In response to a similar request from the Truck Trailer Manufacturers Association, the National Highway Traffic Safety Administration recently prepared a comprehensive discussion of this subject, a copy of which is enclosed for your information. Yours Truly, Trailmaster Tanks, Inc. May 14, 1975 Mr. James C. Schultz Chief Counsel NH 13A - DOT We manufacture transport trailers and with the new weight law, that has been passed, we need some information on the subject of stretching out a trailer. These trailers have already been manufactured and are in use at this time. We need to know, if the way that we plan to stretch out the trailers, if that is within the laws. If you can send us some information on this subject, we will be most appreciative. PHIL MARTINEZ, ENGINEER |
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.