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: aiam1393OpenMr. Lee Moses, Trailer Coach Association, 3855 East LaPalma Avenue, Anaheim, CA, 92806; Mr. Lee Moses Trailer Coach Association 3855 East LaPalma Avenue Anaheim CA 92806; Dear Mr. Moses: This is in response to your telephone request of February 6, 1974 concerning the application of Standard No. 302, *Flammability of Interior Materials.*; The standard applies to passenger cars, multipurpose passenge vehicles, trucks, and buses. It does not apply to trailers, the vehicle category which includes mobile homes and other towed recreational vehicles, but it does apply to motor homes and to those campers that are constructed on new chassis. Accordingly, any of the components listed in paragraph S4.1 that are installed in the occupant compartments of the motor vehicles to which the standard is applicable must meet the standard's requirements.; You also asked whether a State may have a motor vehicle safety standar applicable to vehicles covered by a Federal standard that differs from the requirements of the Federal standard. The answer is no. Under the preemption provision of the National Traffic and Motor Vehicle Safety Act, section 103(d), 15 U.S.C. 1392(d), State motor vehicle requirements, if any, have to be identical to the requirements of the Federal standard. Any differing requirements would be void.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam1669OpenMr. Donald D. Wahlin, President, Stoughton Trailers, 416 South Academy Street, Stoughton, WI 53589; Mr. Donald D. Wahlin President Stoughton Trailers 416 South Academy Street Stoughton WI 53589; Dear Mr. Wahlin: This responds to your October 15, 1974, letter to the Bureau of Moto Carrier Safety asking if a trailer is subject to Standard No. 121, *Air brake systems*, if its buyer certifies, for tax purposes, that the vehicle in fact uses the highways only incidentally.; I have enclosed a discussion of our regulatory authority over moto vehicles, which does not include vehicles intended and sold solely for off-road use. However, we do regulate vehicles which use the highway on a necessary and recurring basis, whether or not this use is infrequent and incidental to the vehicle's working function.; We do not base this distinction on the same considerations as underl excise tax regulations and laws. The statutory definition of 'motor vehicle' and the regulations in the tax area differ from ours, as they are only directed to taxing regular highway users who should bear the burden of maintaining the roads. In contrast, our statute and regulations are directed to safe vehicle design, which is important for all vehicles designed to use the highways, whether or not their use is on a regular basis. We conclude that the revenue considerations involved in tax cases are not relevant to our safety regulation requirements.; Yours truly, Richard B. Dyson, Acting Chief Counsel |
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ID: aiam4191OpenMr. J. Leon Conner, Manager, Long & Associates, Inc., P.O. Box 691, San Angelo, TX 76902; Mr. J. Leon Conner Manager Long & Associates Inc. P.O. Box 691 San Angelo TX 76902; Dear Mr. Conner: This responds to your letter seeking an interpretation of th requirements of 49 CFR S575.104, *Uniform Tire Quality Grading Standards* (UTQGS). Specifically, you asked whether this regulation requires the treadwear testing for a tire size to be conducted only with vehicles that specify the subject tire size either as the original equipment size or as one of the recommended optional tire sizes. The UTQGS does not contain any such provision.; The conditions and procedures to be followed in grading tires fo treadwear under the UTQGS are set forth in S575.104(e). That section specifies tire loading conditions and rim dimensional requirements for the vehicles used in the treadwear testing. However, it does *not* specify that the vehicles used in the treadwear testing can only be used to test tire sizes recommended as either original equipment or optional tires on the vehicle when new. Accordingly, persons testing tires to determine the treadwear grade may mount the tires on any vehicle, provided that the tire and vehicle satisfy all the requirements of S575.104(e), relating to tire construction, inflation pressure, size designation, vehicle loading, and wheel alignment.; You stated in your letter that the UTQGS compliance test procedures used by this agency for conducting its enforcement testing for treadwear grades, currently specify that tire sizes must be tested on vehicles that specify that size as either original equipment or recommended optional size. This specification may have been adopted after the following language appeared in a 1975 preamble to a final rule establishing the UTQGS:; >>>Several commenters suggested that the rule specify all vehicles in given convoy be identical, to reduce variations in projected treadlife. ... Variations in vehicle type, however, do not appear to produce significant variations in treadwear projections. Nevertheless, to minimize such variations, tires will be tested for compliance only on vehicles for which they are available as original equipment or recommended replacement options. 40 FR 23073, at 23076, May 28, 1975.<<<; As explained above, the UTQGS regulation does not specify that th vehicles used in treadwear testing can only be used to test tire sizes recommended as either original equipment or optional tires on the vehicle. The agency's compliance test procedures are only the methods the agency itself uses to determine the appropriate treadwear grade for a tire. Persons outside the agency are not bound by any testing conditions and methods not set forth in the UTQGS itself. Such persons may, therefore, conduct their own testing in a manner different from that specified in NHTSA's compliance test procedures, provided that their testing satisfies all requirements of S575.104(e).; You also stated that the use of different vehicles for treadwea testing of tires will produce measurably different treadwear grades for the tire, even when all the vehicle factors are closely and properly controlled. As quoted above, NHTSA concluded that vehicle-to-vehicle variations 'do not appear to produce significant variations in treadwear projections', when it examined this issue in 1975. However, the agency is currently re-examining the effects of vehicle-to- vehicle variations on treadwear projections, particularly with respect to front-wheel vs. rear-wheel drive vehicles and passenger cars vs. light trucks and vans. If you wish to provide some additional data on this subject, please forward the data to Mr. Barry Felrice, Associate Administrator for Rulemaking, at this address. We would be interested in analyzing whatever data form the basis for your belief that our 1975 conclusion was incorrect.; Please feel free to contact Steve Kratzke of my staff, at this addres or by telephone at (202) 366-2992, if you have any further questions about our UTQGS.; Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam3654OpenMr. Thomas A. Kenny, Secretary/Treasurer, Pulse Marketing Group, Inc., P.O. Box 1324, Elkhart, IN 46515; Mr. Thomas A. Kenny Secretary/Treasurer Pulse Marketing Group Inc. P.O. Box 1324 Elkhart IN 46515; Dear Mr. Kenny: This responds to your recent letter requesting information concernin Safety Standard No. 205, *Glazing Materials*. You are considering marketing a fiberglass reinforced plastic part' that would replace rear windows in buses. You ask whether the standard would be applicable.; The answer to your question is yes. Safety Standard No. 205 specifie performance and location requirements for all glazing materials used on motor vehicles, whether as original equipment or replacement parts. As a manufacturer or fabricator of glazing you would have to certify that your fiberglass product complies with all applicable requirements of the standard. Standard No. 205, and the ANS Z26 standard which is incorporated by reference, specifies three types of plastic materials which may be used in the rear windows of buses (including rear side windows). These are Items 4, 5, and 12 glazing materials. Your fiberglass window may only be used in the rear windows of buses if it complies with the performance requirements of one of these glazing types (Items), i.e., if it passes all of the tests specified for one of these Items. The fact that your product is opaque does not preclude its use, since Items 4, 5, and 12 glazing materials do not have to comply with any luminous transmittance requirements.; You also asked if any approvals are necessary before you market thi product. The answer is no. The agency does not grant prior approvals of motor vehicles or motor vehicle equipment. Section 114 of the National Traffic and Motor Vehicle Safety Act provides that it is the responsibility of the glazing manufacturer or fabricator to determine compliance and to certify that its product complies with all applicable requirements of Safety Standard No. 205. The certification and marking requirements are prescribed in paragraph S6 of Standard No. 205. (I am enclosing a copy of section 114 of the Vehicle Safety Act, which is referenced in paragraph S6.); Please contact Hugh Oates of my staff if you have any further question. Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam2946OpenMr. R. C. Back, Director, Government Relations, P.O. Box 520816, Miami, FL 33152; Mr. R. C. Back Director Government Relations P.O. Box 520816 Miami FL 33152; Dear Mr. Back: This is in reply to your letter of January 23, 1979, in which you aske for confirmation of your interpretation that the new restriction on mounting height of rear side marker lamps applies only to trailers and not to trucks.; This confirms your interpretation. As is stated in Table II of Moto Vehicle Safety Standard No. 108, rear side marker lamps are to be mounted above the road surface 'not less than 15 in., and on the rear of trailers not more than 60 in.'; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam1239OpenMr. Bernard Belier, U.S. Resident Engineer for Citroen S.A, U.S. Technical Research Corp., 801 Second Avenue, New York, New York 10017; Mr. Bernard Belier U.S. Resident Engineer for Citroen S.A U.S. Technical Research Corp. 801 Second Avenue New York New York 10017; Dear Mr. Belier: This is in reply to your letter of July 24, 1973, asking for a interpretation of several aspects of Standard No. 105a.; You have asked the following questions >>>'1. *Paragraph S5.1.2 'Partial failure.*' It is required that '...the remaining portion(s) of the service brak system shall continue to operate...' What is the exact meaning of 'continue to operate'? Does it mean that the remaining portion of the brake system must be permanently fed or does it mean that it is required to have *temporary* braking with the operative portion reserve capability? In this latter case, how many brake applications are required?'<<<; 'Continue to operate' means that the portion of the brake system tha has not failed continues to operate indefinitely, i.e., to the point that it wears out or until a second failure occurs in the brake system. It requires a permanent feed and does not depend upon the reserve capability of operative portion of system.; >>>'2. *Paragraph S5.1.3.3 'Brake power units':* What exactly constitutes the power source? On the Citroen D and models, the front brake circuit is fed by a brake accumulator while the rear brake circuit is fed by the pressure prevailing in the read suspension. The brake accumulator and the rear suspension are fed from the high pressure source (which includes an HP pump, A pressure regulator and a main accumulator)...What is meant by 'inoperative brake power unit'? Does that mean that the high pressure pump *only* is inoperative or also the other components of the power source (main accumulator and regulator)?...What is meant by 'when the inoperative unit is depleted of all reserve capability' (paragraph S5.1.3.3.(ii))? Are we correct in assuming that it means that *only* the main accumulator is depleted of reserve capability? (It is obvious that if one considers that not only the main accumulator, but also the brake accumulator and the rear suspension are depleted, no braking is possible).'<<<; The power source consists of pumps, accumulators and/or back up system such as a separate electric or hydraulic pump, etc. A primary power source would be the pump, while the accumulators would constitute a secondary source and would be the portions used in optional test. A high pressure source would include the pump, regulator and, in Citroen's case, the main accumulator.; 'Inoperative brake power unit' could mean that the (1) main pump i out, but the accumulators are functioning, (2) the main pump is operating but only one brake accumulator is operating, (3) the pump and brake accumulator are operating, but the suspension accumulator is out, (4) the pump or accumulator is out, and the system is operating on reserve or backup pump. This list is meant to be illustrative rather than exhaustive.; 'When then inoperative unit is depleted of all reserve capability means that one of the units (pump, accumulator, etc.) is completely nonfunctional, e.g., the pump has failed, the accumulator has failed, the check valve has failed, etc.; >>>'3. *Paragraph S7.10.2 'Optional procedures'* We believe that the subparagraph 'b' (vehicles with brake power unit applies to our vehicles.; The test procedure mentioned in paragraph S7.10.2(a) cannot be applie to our vehicle since, if the system is depleted of '*any residual* brake power reserve capability', it is obvious that no braking is possible. We believe that the power source *only* should be depleted of any residual reserve (HP pump inoperative, main accumulator depleted), but not the entire brake system. Since by definition, a 'brake power unit' is a unit where the operator action consists 'only of modulating the energy application level, ' but not of supplying energy to the system, it is obvious that no braking is possible if all internal residual energy left in the brake system is depleted (since, in this case, there would be no energy available for braking from either the HP source, the driver or the system).<<<; S7.10.2(b) does apply to Citroen. Your comments on S7.10.2(a) ar correct.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam3204OpenMr. Roger Hagie, Kawasaki Motors Corp., USA, 3630 Garry Avenue, P.O. Box 11447, Santa Ana, California 92711; Mr. Roger Hagie Kawasaki Motors Corp. USA 3630 Garry Avenue P.O. Box 11447 Santa Ana California 92711; Dear Mr. Hagie: This is in response to your letter of January 24, 1980, to Mr. Schwart of my office requesting an interpretation of Federal Motor Vehicle Safety Standard No. 115.; I understand from your letter that Kawasaki Motors Corp., USA, intend to comply with S4.3 of Safety Standard No. 115 by placing the vehicle identification number (VIN) on the certification label of the motorcycles it manufacturers. Since the standard specifies the precise placement of the VIN only for passenger cars and trucks with a GVWR of 10,000 pounds or less (S4.4), placing the VIN on the certification label of motorcycles is authorized.; You also wish to know whether Standard No. 115 precludes Kawasak stamping a model designation and production sequence into the frame near the certification label. As long as the number which you stamp into the frame cannot be mistaken for the VIN because of its length or other factors, this would not be prohibited.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam0582OpenMr. E. G. Nagle, Vice President - Automotive Sales, Allen Industries, Inc., Executive Offices: Honeywell Bldg., 17515 West Nine Mile Road, Southfield, MI, 48075; Mr. E. G. Nagle Vice President - Automotive Sales Allen Industries Inc. Executive Offices: Honeywell Bldg. 17515 West Nine Mile Road Southfield MI 48075; Dear Mr. Nagle: This is in reply to your letter of January 24, 1972, requestin information on possible changes to Motor Vehicle Safety Standard No. 302, 'Flammability of Interior Materials.'; At present, NHTSA is preparing an amendment to the standard based o the notice of proposed rulemaking published May 25, 1971 (36 F.R. 9565), and clarifying other questions pertaining to the standard that have been raised since its issuance. We hope to have this amendment prepared in the near future, but at present we cannot provide information on exact dates. At the same time, if the NHTSA determines that any changes in the standard made by the amendment require additional leadtime, appropriate action will be taken.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam2045OpenMr. Guy A. Catherine, General Sales Manager, Kleber Corporation, 91-31 Queens Blvd. New York, N.Y. 11373; Mr. Guy A. Catherine General Sales Manager Kleber Corporation 91-31 Queens Blvd. New York N.Y. 11373; Dear Mr. Catherine: #This is in response to your letter of June 3 1975, asking whether it is permissible to import into this country tire designed exclusively for racing purposes. #Tires designed to be used exclusively on racing vehicles, *i.e.*, vehicles other than 'motor vehicles' within the meaning of the national Traffic and Motor Vehicle Safety Act, are not regulated by the Federal motor vehicle safety standards, and may be imported. The labeling that you propose to use appears to be appropriate to warn users of their intended purpose. Manufacturers of such equipment should take all reasonable steps to ensure that their products are not misused. #Yours truly, Richard B. Dyson, Assistant Chief Counsel; |
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ID: aiam0078OpenMr. H. Moeller, Research and Development Department, Robert Bosch Corporation, 40-11 - 24th Street, Long Island City, NY 11101; Mr. H. Moeller Research and Development Department Robert Bosch Corporation 40-11 - 24th Street Long Island City NY 11101; Dear Mr. Moeller: Thank you for your letter of May 24, 1968, to Mr. J. E. Leysath of thi Bureau, concerning the testing of automotive flasher devices.; Motor Vehicle Safety Standard 108 specifies that turn signal flasher and vehicular hazard warning signal flashers conform to SAE Standards J590b and J945, respectively. These SAE standards, in turn, require that the test circuitry and test instrumentation conform to SAE Standard J823a. As you noted, the distribution of the 0.10 0.01 ohm series resistance in the standard test circuit (Figure 1 of J823a) is not specified in SAE Standard J823a. Therefore, your recommended distribution, namely, 0.025 0.005 ohms resistance between the power supply (positive terminal) and flasher input terminal, and 0.075 0.005 ohms resistance between the flasher output terminal and the flasher bulbs, would be permitted by SAE Standard J823a.; Flasher units having a ground terminal that is connected with th negative terminal of the power supply may be tested in the standard test circuit of SAE Standard J823a, provided the ground circuitry does not change the required resistance of 0.10 0.01 ohm looking into terminals A-B with the removable shunts in place (see note for Figure 1, SAE J823a).; The above-stated test provisions in no way except the flasher unit from meeting all performance requirements specified in Standard No. 108, including those specified in basically referenced SAE Standards J590b, 'Automotive Turn Signal Flashers,' and J945, 'Vehicle Hazard Warning Signal Flasher.'; Sincerely, David A. Fay, Office of Standards on Accident Avoidance Motor Vehicle Safety Performance Service; |
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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.