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: aiam0470OpenMr. James A. Skinner, REBCO, 8000 Branch Avenue, Clinton, MD 20735; Mr. James A. Skinner REBCO 8000 Branch Avenue Clinton MD 20735; Dear Mr. Skinner: This is in reply to your letter of October 24, 1971, concerning th retention of records of the names and addresses of first purchasers of retread tires that you manufactured prior to October 13, 1971, the date you went out of the retread business.; Under the Tire Identification and Record Keeping Regulation you ar required to maintain the names of first purchasers three years from the time the sale is reported to you or your designee. Therefore, as to those tires manufactured between May 22, 1971 and the date you went out of business, October 24, 1971, you are required to maintain, or have maintained for you the names and addresses of the first purchasers for three years after this information is recorded by you or your designee.; Sincerely, Lawrence R. Schneider, Chief Counsel |
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ID: aiam4433OpenMr. Charles W. Pierson 404 Williams Street Sturgis, MI 49091; Mr. Charles W. Pierson 404 Williams Street Sturgis MI 49091; "Dear Mr. Pierson: This responds to your letter in which you mad several observations about dynamic testing requirements generally in our safety standards. I am pleased to have this opportunity to explain those requirements for you. You began by observing that this agency has been moving to replace static testing requirements (tests in which individual vehicle components are subjected to specified levels of slowly applied force in a laboratory test) with dynamic testing requirements (e.g., tests in which a vehicle is crashed into a barrier and anthropomorphic test dummies are used to measure the protection provided by the vehicle to occupants in a crash). You then suggested that there were several potential difficulties or misinterpretations that could arise with dynamic testing. First, you asked which of the several standardized human physical dimensions should be used to determine if a vehicle complies with our safety standards that refer to a specified percentile child or adult. For instance, section S7.1.1 of Standard No. 208, Occupant Crash Protection (49 CFR /571.208) requires the lap belt portion of a seat belt assembly to adjust to fit persons whose dimensions range from a 50th percentile 6 year old child to a 95th percentile adult male, while the shoulder belt portion of a seat belt assembly must adjust to fit persons whose dimensions range from a 5th percentile adult female to a 95th percentile adult male. When our regulations refer to a specific size for a vehicle occupant, the regulations also clearly specify the dimensions and weights of the vehicle occupants to which we are referring. Section S7.1.3 of Standard No. 208 sets forth the critical weights and dimensions of all vehicle occupants referred to in that standard. The critical weights and physical dimensions for all of the anthropomorphic test dummies used to measure compliance with our safety standards are set forth in 49 CFR Part 572, Anthropomorphic Test Dummies. Second, you noted that testing facilities will conduct crash testing, but will not certify those results. This practice on the part of the testing facilities is consistent with the requirements of the National Traffic and Motor Vehicle Safety Act (the Safety Act, 15 U.S.C. 1381 et seq.). Section 114 of the Safety Act (15 U.S.C. 1403) explicitly requires every manufacturer to certify that each of its vehicles or items of equipment conforms to all applicable safety standards. Hence, regardless of how a testing facility presents test results to a manufacturer, it is the manufacturer of the product, not the testing facility, that is statutorily responsible for certifying that each of its products complies with all applicable safety standards. Third, you stated that 'laws requiring certification usually do not require the actual crash test to be performed.' You are correct to the extent that you are suggesting that the Safety Act does not require manufacturers to conduct any testing before certifying that its product complies with all applicable safety standards. The Safety Act requires only that the manufacturer exercise due care in certifying its products compliance with the safety standards. It is up to the individual manufacturer in the first instance what data, test results, computer simulations, engineering analyses, or other information it needs to enable it to certify that each of its products comply with all applicable safety standards. However, for purposes of enforcing the safety standards, this agency conducts spot checks of products after they have been certified by the manufacturer. NHTSA purchases the products and tests them according to the procedures specified in the applicable standard. If the standard specifies a crash test, NHTSA conducts the crash test according to the specified procedures. Fourth, you asked how you could obtain a copy of the Society of Automotive Engineers (SAE) Recommended Practice J833. This and all other SAE materials can be obtained by writing to: Customer Service Department, Publications Group, SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. The SAE's Customer Service Department can also be contacted by telephone at (402) 776-4970. Fifth and finally, you suggested that the formula used to calculate the head injury criterion (HIC), set forth in sections S6.1.2 and S6.2.2 of Standard No. 208, is relatively complex, so the HIC could be miscalculated. It is true that any mathematical calculation can be performed incorrectly. Nevertheless, the formula for calculating the HIC yields only one correct result for any set of variables. This agency has not experienced any difficulties in calculating the proper HIC from any test results, and is not aware of any difficulties that have been encountered by any manufacturers in making such calculations. Hence, we do not believe there are any problems associated with the HIC formula. I hope this information is helpful. If you have any further questions or need additional information in this area, please feel free to contact me. Sincerely, Erika Z. Jones Chief Counsel"; |
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ID: aiam0923OpenMr. P. J. P. Morris, Manager, Vehicle Legislation, Whitley Technical Centre, Chrysler United Kingdom Ltd., Coventry CV3 4CB, England; Mr. P. J. P. Morris Manager Vehicle Legislation Whitley Technical Centre Chrysler United Kingdom Ltd. Coventry CV3 4CB England; Dear Mr. Morris:#This is in reply to your letter of November 7, 1972 about Federal Motor Vehicle Safety Standard No. 102 as applied to a four speed automatic gear box.#As described, your transmission functions as follows:#>>>'When the gear selector is in any forward position and the vehicle speed falls the automatic mechanism will cause the drive ratio to eventually fall to the lowest gear and thereafter to disengage at about 6 mph leaving the vehicle in a state of 'free-wheel'.'<<<#Paragraph S3.1.2, Transmission Braking Effect, requires that:#>>>'In vehicles having more than one forward transmission gear ratio, one forward drive position shall provide a greater degree of engine braking than the highest speed transmission ratio at vehicle speeds below 25 miles per hour.'<<<#Your transmission, as described, does not meet this requirement, since, in downshifting, the drive ratio would disengage at about 6 miles per hour leaving the vehicle in a state of 'free-wheel' with no engine braking at all.#Sincerely, E. T. Driver, Director, Office of Operating Systems, Motor Vehicle Programs; |
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ID: aiam1631OpenMr. Orville A. Feikema, 18225 Burnham Avenue, Lansing, IL 60438; Mr. Orville A. Feikema 18225 Burnham Avenue Lansing IL 60438; Dear Mr. Feikema: This is in reply to your letter of September 30, 1974, requestin copies of Federal laws and regulations dealing with the manufacture and sale of automobiles, and asking specifically for information regarding the responsibility of persons who modify for resale vehicles which, prior to modification, conform fully to Federal requirements.; I am enclosing a copy of the National Traffic and Motor Vehicle Safet Act of 1966 (15 U.S.C. 1381 *et seq*.) and the Motor Vehicle Information and Cost Savings Act (15 U.S.C. S 1901 *et seq*.). These two laws contain this agency's authority to regulate the manufacture of motor vehicles. The former statute has very recently been amended but we do not as yet have copies of the amended language for distribution. I have also enclosed information on where you may obtain copies of the Federal motor vehicle safety standards and regulations. The Environmental Protection Agency administers laws and regulations which deal with vehicle pollution. Questions regarding these requirements should be directed to Mr. Eric Stork, Environmental Protection Agency, Room 1219, East Tower, 401 'M' Street, SW, Washington, DC 20460. In addition, there is legislation of which you are no doubt aware which require manufacturers to affix the retail price and other information to new vehicles. This legislation can be found at 15 U.S.C. S 1231 *et seq*.; With respect to your question regarding persons who modify vehicles the NHTSA has issued requirements which apply specifically to this situation. Under Section 114 of the Vehicle Safety Act (15 U.S.C. S1403) and regulations issued thereunder (49 CFR Parts 567, 568), manufacturers of motor vehicles must certify each vehicle's conformity to all applicable safety standards by affixing to the vehicle a label containing certain specified information. Persons who modify vehicles in the manner you describe before their sale to the user are considered to be vehicle alterers in these regulations, and are required to conform to requirements set forth in 49 CFR S567.7 and S568.8.; If you have further questions of a specific nature after you hav reviewed the applicable requirements we will be happy to answer them for you.; Yours truly, Richard B. Dyson, Acting Chief Counsel |
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ID: aiam0889OpenMr. Dwight A. Warren, Personnel Aide - Safety, Personnel Department, 500 Municipal Building, 251 West Washington, Phoenix, AZ 85003; Mr. Dwight A. Warren Personnel Aide - Safety Personnel Department 500 Municipal Building 251 West Washington Phoenix AZ 85003; Dear Mr. Warren: Your letter of September 18, 1972, to our Regional Administrator i Region IX, was referred to this office for a direct reply.; The information you desire is contained in the enclosed copy of Federa Motor Vehicle safety Standard (FMVSS) No. 215, Exterior Protection.; The standard applies to new vehicles manufactured for sale in th United States. It is my understanding that push-bar type bumpers are installed after the vehicles have been purchased from the manufacturer. This type of installation is not in conflict with the requirements of FMVSS No. 215.; Thank you for your interest in motor vehicle safety, and if we can b of further assistance, please let us know.; Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicl Programs; |
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ID: aiam4063OpenMr. Donald L. Stephens, Director of Technology, Paccar Technical Center, 1261 Highway 237, Mount Vernon, WA 98237; Mr. Donald L. Stephens Director of Technology Paccar Technical Center 1261 Highway 237 Mount Vernon WA 98237; Dear Mr. Stephens: This responds to your letter of September 13, 1985, asking tw questions regarding the legality of an air brake system which proportions the amount of air brake pressure delivered to the drive axles of a tandem drive tractor. By 'proportions', you refer to the reduction of the applied air pressure at all treadle positions in rough proportion to the load carried by the tires. Your first question is whether an air brake system such as the one you described would be legal if it otherwise complies with Standard No. 121, *Air Brake Systems*, (49 CFR S571.121). You also would like to know if it would be legal for you to remove the front axle limiting valve in the design you propose.; By way of background information, this agency does not give approval of motor vehicles or equipment. The National Traffic and Motor Vehicle Safety Act places the responsibility on the manufacturer to ensure that its vehicles or equipment comply with applicable requirements. A manufacturer then certifies that its vehicles and equipment comply with all applicable standards. The following represents our opinion based on the facts provided in your letter.; In response to your first question, the NHTSA's regulations do no address the matter of proportioning. Standard No. 121 does not specify the design of brake system components, rather, it establishes a performance level. A brake system which proportions the amount of air brake pressure delivered to the drive axles of a tandem drive tractor is not prohibited if it otherwise meets Standard No. 121.; As to your second question, NHTSA regulations do not require nor d they prohibit a vehicle from having a front axle limiting valve. Therefore, vehicles need not have these valves in order to meet our standard and you are not prohibited from removing the front axle limiting valve in the design you propose. In fact, an interim technical report of the NHTSA Heavy Duty Vehicle Brake Research Program, published April, 1985, concluded that automatic front axle limiting valves in many vehicles significantly degrade straight line performance in the empty mode and on wet surfaces. However, if a vehicle does have an automatic pressure limiting valve, it must meet the requirements set out in S6.1.8.1 of Standard 121.; Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam4599OpenMr. Thomas C. Gravengood Agap'e Plastics Inc. Grand Rapids, MI 49504; Mr. Thomas C. Gravengood Agap'e Plastics Inc. Grand Rapids MI 49504; Dear Mr. Gravengood: This is in reply to your letter of April 3, l989 to this Office enclosing samples of plastic lenses. Your company manufactures 'heated lights' which appear beneficial in melting snow that accumulates on them in the winter months. In your letter, you stated: 'All lights, lenses, and materials to assemble the heated safety lights have already been certified and passed the Motor Vehicle Safety Standard No. 108. We have been advised by the National Highway Traffic Safety Administration that there is no motor vehicle safety standard no. for heated lights. In order for us to do business at the O.E.M. level we require a letter of approval from you to us that we may pass on to our customers so they may start ordering and we may start producing.' We have no authority to 'approve' or 'disapprove' items of motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, an equipment manufacturer 'approves' each of its own products that are subject to a Federal motor vehicle safety standard by certifying that it meets all applicable Federal motor vehicle safety standards, or (if it is a vehicle manufacturer), that the vehicle on which the lamp is installed, complies with the standards. However, we can advise you of the relationship of your product to Standard No. 108. This should prove helpful in dealings at the O.E.M. level. There are two types of O.E.M. lighting equipment: lamps that are required by Standard No. 108, and supplementary lamps that do not come under its coverage. Although your product literature indicates that the highmounted heated taillamp supplements the original equipment lamp, it is not clear whether the heated signal lamp serves as the required signal lamp or is a supplement to the original equipment. Accordingly, this letter discusses how Standard No. 108 treats both original required and original supplemental lighting equipment. If you are the manufacturer of original lighting equipment required by Standard No. 108, but not the manufacturer of the vehicle on which it is installed, the vehicle manufacturer, and not you, has the legal responsibility under the Act and Standard No. 108 of ensuring that the equipment complies with the standard, and of certifying that the vehicle meets all applicable Federal motor vehicle safety standards. As a practical matter, however, vehicle manufacturers generally insist that equipment manufacturers provide assurance that their products meet Federal standards, but the 'certification' they may insist upon is not required by the Act. You are correct that there is no standard that applies to heated lamps as such. The Federal standard that applies is the one imposed by Standard No. 108 for the particular equipment item (taillamps or signal lamps in this instance). If you are manufacturing a lamp as an original equipment supplement to required original lighting equipment, the burden remains on the vehicle manufacturer who installs it. The only restriction on a supplementary lamp that Standard No. 108 imposes is that it not impair the effectiveness of the required lighting equipment (paragraph S4.1.3). Your lamps 'splice into' the wiring for the taillamps and 'marker lamps', according to your product literature. Therefore, it is incumbent upon the vehicle manufacturer to ensure that this installation does not negatively affect the performance of the required taillamps and signal lamps, or otherwise impair its effectiveness. If the vehicle manufacturer determines that no impairment exists, then it may certify that its vehicles comply with all applicable Federal motor vehicle safety standards. Observing that the product literature depicts the heated taillamp installed in the upper corners of a school bus body, we must also call attention to an additional provision of Standard No. 108. The location depicted is one that is frequently used for the clearance lamps required by Standard No. 108. Paragraph S4.4 of Standard No. 108 forbids the optical combination of clearance lamps and taillamps. Thus, your lamp cannot optically combine these two functions if it is to be used as new vehicle equipment. Other enclosures to your letter indicate that at present the heated lamp is being installed on buses in use, that is to say, as non-original equipment. The requirements imposed by Standard No. 108 and the Act for aftermarket manufacturers of lighting equipment differ from those for original equipment. If the lamp you produce is intended to replace an original equipment certified lamp, it is considered replacement equipment. As a manufacturer of a replacement taillamp or signal lamp, the legal obligation to produce a complying equipment item falls squarely upon you, as does the certification responsibility. If the lamp is intended only to replace a supplemental lamp, you are not required to certify. However, there may be instances in which your lamp is interchangeable with original certified equipment, and even though you may not intend it as replaceable lighting equipment, you may encounter questions from state and federal authorities if it is not manufactured and certified in accordance with Standard No. 108. Finally, you should be aware of your responsibilities under the Act in the event that your products do not comply with Standard No. 108, or incorporate a safety related defect (an example would be the inability of the lens to withstand the heat produced during the lamp's operation without warping or cracking). If you or this agency determine that a noncompliance or safety related defect occurs in any item of replacement equipment that you manufacture, you have the obligation to notify purchasers, and to remedy the problem through repair, repurchase, or replacement of the item. With respect to original equipment, this obligation falls upon the manufacturer of the vehicle on which it is installed. If you have any further questions we shall be happy to answer them. We are returning your samples. Sincerely, Stephen P. Wood Assistant Chief Counsel for Rulemaking; |
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ID: aiam1261OpenHonorable James R. Jones, House of Representatives, Washington, DC 20515; Honorable James R. Jones House of Representatives Washington DC 20515; Dear Mr. Jones: This is in reply to your letter of July 23, 1973, forwarding to u correspondence from Mr. G. N. Nichols, President, Midwestern Products, Incorporated, Tulsa, concerning the applicability of Federal regulations to an air suspension auxiliary axle manufactured by Midwestern Products. According to the manufacturer's advertising brochure, this axle, the 'Micro- Air Retractable Safety Axle,' is intended to be used on pick-up and bobtail trucks, particularly in the recreational vehicle and related fields.; There are presently no Federal motor vehicle safety standards o regulations that apply to the manufacture of these axles. However, persons who install them on *new* pick-up trucks or other vehicle types (a 'new vehicle under the National Traffic and Motor Vehicle Safety Act is one that has not yet been sold to a user) may be considered as vehicle alterers under provisions of NHTSA certification regulations which are to become effective February 1, 1974 (Docket No. 72-27, copy enclosed), and would be required to affix to the vehicle the label described in section 567.7 of those regulations.; Midwestern Products should be aware of these requirements whether i installs the Micro-Air axle or whether the installation is done by other parties. In the former case Midwestern would be responsible for affixing the required label, and in the latter it should provide the relevant information for the label regarding weight ratings to the party making the installation.; The NHTSA does not maintain a mailing list to provide copies of NHTS notices and regulations. Copies are available as indicated on the enclosed sheet, 'Where to Obtain Motor Vehicle sAfety Standards and Regulations.'; We are pleased to be of assistance. Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicl Programs; |
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ID: aiam2764OpenMr. W. W. Schwartz, Technical Engineer, Research and Development Dept., Vetter Fairing Company, 1150 Laurel Lane, San Luis Obispo, CA 93401; Mr. W. W. Schwartz Technical Engineer Research and Development Dept. Vetter Fairing Company 1150 Laurel Lane San Luis Obispo CA 93401; Dear Mr. Schwartz: This is in reply to your letter of February 1, 1978, on motorcycl headlighting.; You have asked whether the prohibition in SAE J580a *Sealed Bea Headlamp* against headlamp covers applies to a motorcycle. You have also asked the reason for the prohibition.; Sae J580a *Sealed Beam Headlamp* is incorporated by reference in Tabl III of Standard No. 108 as one of the standards applicable to headlamps for use on multipurpose passenger vehicles, trucks, and buses whose overall width is less than 80 inches. One of the SAE standards incorporated by reference for motorcycle headlighting is J584 which, as an option, allows motorcycles to be equipped with headlamps 'meeting the requirements of SAE J579' (i.e. passenger car sealed beam headlamps). There is no reference in J479a to J580a, and we therefore do not read the prohibition against headlamp covers as applying to motorcycles equipped with sealed or unsealed headlamps.; The reason for the prohibition is the degradation in light output tha can result from condensation under unsealed glass covers or from obscuration by grilles in front of the lens.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam0759OpenMr. T. C. McLaughlin, McLaughlin Equipment Co., Box 2765, 320 27th Street, Fargo, ND 58102; Mr. T. C. McLaughlin McLaughlin Equipment Co. Box 2765 320 27th Street Fargo ND 58102; Dear Mr. McLaughlin: This is in reply to your letter of May 17, 1972, concerning th remounting of old school bus bodies on new chassis. You indicate that this practice is occurring in North Dakota, enclose an advertising brochure of a company that performs the service, and also enclose a copy of a letter from Mr. Robert B. Klure of the Divco-Wayne Corporation which discusses possible safety problems that may result from this practice. You have asked us to outline actions and procedures that can be taken by the NHTSA or your office to curtail this practice.; The NHTSA considers the mounting of an old school bus body on a ne chassis to be manufacturing of a vehicle, which must conform to all applicable motor vehicle safety standards in effect on the day of the manufacture of the chassis, or of the completed vehicle. The failure of a school bus manufactured in this fashion to conform to applicable standards would be a violation of section 108(a)(1) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1397(a)(1)), and could subject its manufacturer to civil penalties and other sanctions. In addition, such vehicles must be certified as conforming to all applicable standards, and the failure of a manufacturer to certify can also result in the imposition of similar sanctions.; It appears from the discussion of safety problems in Mr. Klure's lette that the mounting of old school bus bodies on new chassis creates safety problems that the NHTSA might consider to be safety related defects. If a finding is made by NHTSA that such a defect exists, the manufacturer would be required to notify owners of the defect, and the NHTSA would probably urge the manufacturer to conduct a recall campaign.; In either case the NHTSA will take steps to see that all manufacturer are complying with NHTSA requirements. You can assist us by providing the names of companies which you believe are engaging in this practice. This information should be sent to Mr. Francis Armstrong, Director, Office of Standards Enforcement, National Highway Traffic Safety Administration, 400 7th Street, S.W., Washington, DC 20590.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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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.