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: aiam0891OpenMr. Francois Louis, Manager, Technical Standards Department, Renault, Inc., 100 Sylvan Avenue, Englewood Cliffs, NJ 07632; Mr. Francois Louis Manager Technical Standards Department Renault Inc. 100 Sylvan Avenue Englewood Cliffs NJ 07632; Dear Mr. Louis: This is in reply to your letter of October 16, 1972, concerning th seat adjustment procedures of S8.1.2 of Motor Vehicle Safety Standard No. 208.; As described in your letter, some models manufactured by Renault hav front seats that can be adjusted to an extreme forward position to allow the reclining seat back to be fully lowered. You imply that this position cannot be used for driving the vehicle, and ask whether the 'forwardmost' position referred to in S8.1.2 could be interpreted to be the forwardmost *driving* position.; The purpose of S8.1.2 is to specify an adjustment position that i appropriate for the 50th percentile adult male occupant used in the standard's barrier tests. If the adjustment range is determined by using the extreme forward position you describe, the midway point would no longer be appropriate for the 50th percentile adult male size. It is therefore consistent with the purpose of S8.1.2 to exclude the extreme, non-driving positions in determining the midway adjustment position.; However, despite the references in some parts of the standard to a occupant of the 5th percentile adult female size, the adjustment range specified in S8.1.2 does not refer to this or any other size of occupant and we are of the opinion that no occupant size specification can be read into the section.; We would consider a position to be outside the range used to determin the midway point of S8.1.2 if it cannot reasonably be used for driving and if it is separated from other positions by a distance greater than the normal distance between positions. It would appear that the position described in your letter meets these criteria and that it should therefore be excluded in determining the midway position under S8.1.2.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam1783OpenMr. J. L. Chancey, Trail-O-Matic, Inc., P.O. Box 2367, Jacksonville, FL 32203; Mr. J. L. Chancey Trail-O-Matic Inc. P.O. Box 2367 Jacksonville FL 32203; Dear Mr. Chancey: This responds to Trail-O-Matic's January 21, 1975, question whether trailer manufactured from the running gear and suspension of an existing trailer and a newly- fabricated frame and upper structure would qualify as a rebuilt vehicle that would not have to be certified as conforming to the requirements of Standard No. 121, *Air brake systems*.; The answer to your question is no. In determining that a buildin operation constitutes the repair of an existing vehicle, and not the manufacture of a new vehicle, the NHTSA requires that, as a minimum, the running gear and frame of the existing vehicle be used in the building operation. For your information, I have enclosed a letter which discusses a similar operation in the trailer industry.; Standard No. 121, therefore, applies to the manufacture of trailer described in your letter.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam1279OpenMr. D. P. Peck, Technical & Safety Manager, Triumph Motors, British Leyland UK Limited, Conley, Coventry, 0V4 9DB, England; Mr. D. P. Peck Technical & Safety Manager Triumph Motors British Leyland UK Limited Conley Coventry 0V4 9DB England; Dear Mr. Peck:#This is in reply to your letter of September 11, 1973 asking whether a console-mounted diagram depicting proper placement of heating controls to activate the defrost mode is a 'symbol' within the meaning of Standard No. 101 and whether it is therefore prohibited.#We do not consider the diagram a symbol since it does not itself identify a control, but depicts only how that control is to be placed in a certain mode. Its use is therefore permitted.#Yours truly, Richard B. Dyson, Assistant Chief Counsel; |
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ID: aiam4581OpenMr. Keith A. McDowell Vice President - Engineering Transportation Products Group American Seating Company 901 Broadway, N.W. Grand Rapids, MI 49504; Mr. Keith A. McDowell Vice President - Engineering Transportation Products Group American Seating Company 901 Broadway N.W. Grand Rapids MI 49504; "Dear Mr. McDowell: This responds to your recent letter asking thi agency to 'provide guidelines for the design and installation of seat belt assemblies on large buses (over 10,000 pounds GVW).' You explained that you were interested in this information for passenger seats of large buses used in transit service, not as school buses. I am happy to be able to explain our requirements to you. Standard No. 208, Occupant Crash Protection (49 CFR /571.208) sets forth the crash protection requirements applicable to most vehicle types. Section S4.4 of that standard sets forth the requirements applicable to large buses other than school buses. That section requires large buses to have either a complete automatic protection system for the bus driver's seating position, or a seat belt assembly that conforms with Standard No. 209 at the driver's seating position. Standard No. 208 does not specify any requirements for either an automatic protection system or seat belt assemblies to be installed at any other seating positions in large buses. Standard No. 210, Seat Belt Assembly Anchorages (49 CFR /571.210) also includes requirements applicable to the anchorages for any belt assemblies installed at the driver's seating position on large buses. Specifically, section S4.1.2 of Standard No. 210 provides that: 'Seat belt anchorages for a Type 1 or Type 2 seat belt assembly shall be installed for each designated seating position, except a passenger seat in a bus or a designated seating position for which seat belt anchorages for a Type 2 seat belt assembly are required by S4.1.1.' As with Standard No. 208, Standard No. 210 exempts passenger seats in large buses from its requirements. Finally, Standard No. 209, Seat Belt Assemblies (49 CFR /571.209) sets forth requirements applicable to all seat belt assemblies for use in motor vehicles, including large buses. Thus, any seat belt assembly installed at the driver's position in a large bus would have to be certified as complying with Standard No. 209, as would any seat belt assembly voluntarily provided by a manufacturer for passenger seating positions in a large bus. In short, our standards do not require seat belt assemblies to be installed in passenger seats of large buses, but any seat belt assemblies that are installed at those positions would have to comply with Standard No. 209. Your letter indicated that you were generally aware of the fact that seat belt assemblies were not required to be installed at passenger seating positions of large buses. Nevertheless, you asked us to provide you with 'guidelines' for such installations, in response to the continuing demand for such installations by your company's customers. As a policy matter, NHTSA does not provide the sort of guidelines you have requested. The National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1381 et seq.) sets forth certain specific requirements that must be satisfied by each of the Federal motor vehicle safety standards established by this agency. Among these requirements are that each safety standard shall be practicable, meet the need for motor vehicle safety, and be stated in objective terms (section 103(a) of the Safety Act) and each standard shall be reasonable, practicable, and appropriate for the particular type of vehicle for which it is prescribed (section 103(f)(3) of the Safety Act). NHTSA has determined that the current requirements of Standards No. 208 and 210, which do not apply to passenger seats in large buses, meet all of the statutory criteria. The issuance of 'guidelines' specifying measures beyond those required by our standards could readily be misinterpreted as an agency decision that these additional measures are necessary to satisfy the criteria of the Safety Act, or indirectly force manufacturers to comply with the 'guidelines,' in addition to the standards issued under the Safety Act. Either or both of these results would be inappropriate for passenger seats on large buses, because the information currently available to NHTSA indicates that no additional requirements are necessary in this area. Indeed, if the agency were to learn of additional information suggesting the current requirements no longer meet all the statutory criteria, and that requirements for the installation of seat belt assemblies at passenger seats of large school buses would meet all the statutory criteria, we would have an obligation to consider changing the applicable standards. Any such change would be required to be made through the ordinary, notice-and-comment rulemaking process, rather than through issuance of supplemental guidelines. I hope this information is helpful. Sincerely, Erika Z. Jones Chief Counsel"; |
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ID: aiam3244OpenMr. Robert G. Szabo, Van Ness, Feldman & Sutcliffe, Suite 500, 1220 Nineteenth Street, N.W., Washington, D.C. 20036; Mr. Robert G. Szabo Van Ness Feldman & Sutcliffe Suite 500 1220 Nineteenth Street N.W. Washington D.C. 20036; Dear Mr. Szabo: This responds to your recent letter requesting information concernin the legal ramifications of converting motor vehicles fuel systems to operate on both gasoline and compressed gas. I am enclosing a copy of a letter the agency issued last year which discussed the Federal law concerning auxiliary gasoline tanks and the conversion of gasoline-powered vehicles to propane. The discussion in that letter should answer all of your questions. If, however, you require more information, please contact Hugh Oates of my office at 202-426-2992.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam2005OpenGerhard P. Reichel, Volkswagen of America, Inc., Englewood Cliffs, N.J. 07632; Gerhard P. Reichel Volkswagen of America Inc. Englewood Cliffs N.J. 07632; Dear Mr. Reichel: Please forgive the delay in responding to your letter of April 10 1975, requesting an interpretation of S4.3, the placarding requirements, of Federal Motor Vehicle Safety Standard No. 110, *Tire Selection and Rims--Passenger Cars.; You have proposed a format for presenting vehicle capacity weight which is designed to accommodate, with a single placard, several different model configurations. The NHTSA has not objection to this format, provided that the weights listed are correct.; Sincerely, Frank Berndt, Acting Chief Counsel |
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ID: aiam0038OpenMr. H. F. Barr, Vice President, General Motors Technical Center, Warren, MI 48090; Mr. H. F. Barr Vice President General Motors Technical Center Warren MI 48090; Dear Mr. Barr: Thank you for your letter of November 13, 1967, in which approval of dynamic inertia load test procedure, as set forth in paragraph S4.3 of Federal Motor Vehicle Safety Standard No. 206, was requested.; This is to advise that the proposed procedure, as outlined in th enclosure to the referenced letter, is approved for the transverse inertia load portion of the standard test requirements.; Thank you for your continued cooperation in achievement of our mutua goals in motor vehicle safety.; Sincerely, William Haddon, Jr., M.D., Director |
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ID: aiam4978OpenMr. Masashi Maekawa Director, Technical Division Ichikoh Industries, Ltd. 80 Itado, Isehara City Kanagawa, 259-11, Japan; Mr. Masashi Maekawa Director Technical Division Ichikoh Industries Ltd. 80 Itado Isehara City Kanagawa 259-11 Japan; "Dear Mr. Maekawa: This responds to your letter of February 21, 1992 asking for a clarification of our letter of December 18, 1991. In that letter we discussed 'a combination tail/stop lamp that would be mounted on the deck lid ('Lamp B') immediately adjacent to a combination tail\stop lamp that is mounted on the vehicle body ('Lamp A')'. You informed us that each lamp complied with the requirement for effective projected luminous lens area, but that neither complied with photometric requirements. You asked whether Ichikoh could consider the two adjacent lamps as one lamp for purposes of measuring photometrics. We replied that it was not possible to consider the two lamps as one, and that we regarded the lamp that was on the vehicle body as the one that should be designed to conform to Standard No. 108. You have asked whether this advice is consistent with an interpretation given Mazda on June 28, 1985, with respect to a similar design. That letter informed Mazda that compliance of the design would be judged with the vehicle in its normal driving position, thereby implicitly agreeing that the two lamps could be considered one for photometric purposes. The difference in the interpretations originated in the way each manufacturer described its design. Ichikoh referred to its design as two adjacent lamps. Mazda described its configuration as a (single) lamp constructed so that a portion of it is fixed to the body and a portion on the decklid. Our review of the two designs shows that they are essentially similar, and that the Mazda design comprises, in fact, two adjacent lamps. As it was not our intent to change the earlier interpretation, we confirm that the June l985 interpretation remains valid, and that the December 1991 letter is overruled to the extent that it is inconsistent with it. Sincerely, Paul Jackson Rice Chief Counsel"; |
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ID: aiam0192OpenMr. Warren M. Heath, Commander, Engineering Section, Department of California Highway Patrol, P. O. Box 898, Sacramento, CA 95804; Mr. Warren M. Heath Commander Engineering Section Department of California Highway Patrol P. O. Box 898 Sacramento CA 95804; Dear Mr. Heath: Thank you for your letter of December 8, 1969, concerning alternat flashing of side marker lamps with turn signal lamps.; Alternate flashing sidemarker lamps are permitted in paragraph S3.5 o Motor Vehicle Safety Standard No. 108 for signaling purposes, however, they must not impair the effectiveness of the turn signal lamps as required in paragraph S3.1.2.; Sincerely, Charles A. Baker, Office of Standards on Accident Avoidance Motor Vehicle Safety Performance Service; |
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ID: aiam2455OpenMr. B. R. Weber, Executive Vice President, Wesbar Corporation, Box 577, West Bend, WI, 53095; Mr. B. R. Weber Executive Vice President Wesbar Corporation Box 577 West Bend WI 53095; Dear Mr. Weber: This is in reply to your letter of October 28, 1976, asking severa questions with respect to that portion of paragraph S4.4.1 of Motor Vehicle Safety Standard No. 108 which prohibits the optical combination of clearance and tail lamps. You have also expressed your concern, in a recent telephone conversation with Mr. Vinson of my staff, about the ACUTEK interpretation of October 22, 1976, to be discussed below.; The distinction between the hypothetical lamp in Question 2 of you letter of September 7, 1976, and the Acutek lamp is that there is no opaque barrier wall in the former, separating the tail lamp bulb and the clearance lamp bulb, while in the latter the barrier rises to the base of the bulb. Since Standard No. 108 does not require separate compartments (i.e., an opaque barrier) for tail lamps and clearance lamps, it is obvious that the prohibition against optical combination means that (a) a single bulb may not perform both functions and (b) a single bulb must not be perceived as performing both functions. This was the rationale behind Mr. Driver's advice to Acutek that the available data indicated 'that when the tail lamp bulb [on the Acutek lamp] is activated independently from the clearance lamp bulb, and vice versa, there is no appreciable amount of incidental light emitted from the lens of the clearance lamp,' and that 'the amount of light 'spill' appears to be so small that it would not be interpreted (by a driver following the vehicle on which it is installed) as illuminating the lens of the tail lamp when operated in the clearance lamp mode, and vice versa.'; If you apply this general principle to the questions you asked then think you will have the answers. The principle is necessarily dependent upon the candlepower output of any lamp to which it is applied, a value not given in your questions. Thus, the principle cannot be quantified and the determination of the extent of light spill is necessarily subjective, and certification is dependent upon a manufacturer's good faith in attempting to achieve compliance.; After reviewing this matter I must admit that I am curious as to th safety rationale behind the prohibition. Paragraph S4.4.1 had its genesis in a similar provision in Bureau of Motor Carrier Safety regulations (49 CFR 393.22(b)(3), formerly 393.22(c)) and was adopted in conformance with it. The Society of Automotive Engineers, however, does not prohibit combining these lamps. If clearance lamps are mounted below 72 inches--the maximum allowable mounting height for tail lamps--it may be that they could be combined with tail lamps, without any detriment to safety, and at a saving to the consumer. Perhaps you would like to comment on this.; Sincerely, Frank A. Berndt, 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.