NHTSA Interpretation File Search
Overview
NHTSA's Chief Counsel interprets the statutes that the agency administers and the standards and regulations that it issues. Members of the public may submit requests for interpretation, and the Chief Counsel will respond with a letter of interpretation. These interpretation letters look at the particular facts presented in the question and explain the agency’s opinion on how the law applies given those facts. These letters of interpretation are guidance documents. They do not have the force and effect of law and are not meant to bind the public in any way. They are intended only to provide information to the public regarding existing requirements under the law or agency policies.
Understanding NHTSA’s Online Interpretation Files
NHTSA makes its letters of interpretation available to the public on this webpage.
An interpretation letter represents the opinion of the Chief Counsel based on the facts of individual cases at the time the letter was written. While these letters may be helpful in determining how the agency might answer a question that another person has if that question is similar to a previously considered question, do not assume that a prior interpretation will necessarily apply to your situation.
- Your facts may be sufficiently different from those presented in prior interpretations, such that the agency's answer to you might be different from the answer in the prior interpretation letter;
- Your situation may be completely new to the agency and not addressed in an existing interpretation letter;
- The agency's safety standards or regulations may have changed since the prior interpretation letter was written so that the agency's prior interpretation no longer applies; or
- Some combination of the above, or other, factors.
Searching NHTSA’s Online Interpretation Files
Before beginning a search, it’s important to understand how this online search works. Below we provide some examples of searches you can run. In some cases, the search results may include words similar to what you searched because it utilizes a fuzzy search algorithm.
Single word search
Example: car
Result: Any document containing that word.
Multiple word search
Example: car seat requirements
Result: Any document containing any of these words.
Connector word search
Example: car AND seat AND requirements
Result: Any document containing all of these words.
Note: Search operators such as AND or OR must be in all capital letters.
Phrase in double quotes
Example: "headlamp function"
Result: Any document with that phrase.
Conjunctive search
Example: functionally AND minima
Result: Any document with both of those words.
Wildcard
Example: headl*
Result: Any document with a word beginning with those letters (e.g., headlamp, headlight, headlamps).
Example: no*compl*
Result: Any document beginning with the letters “no” followed by the letters “compl” (e.g., noncompliance, non-complying).
Not
Example: headlamp NOT crash
Result: Any document containing the word “headlamp” and not the word “crash.”
Complex searches
You can combine search operators to write more targeted searches.
Note: The database does not currently support phrase searches with wildcards (e.g., “make* inoperative”).
Example: Headl* AND (supplement* OR auxiliary OR impair*)
Result: Any document containing words that are variants of “headlamp” (headlamp, headlights, etc.) and also containing a variant of “supplement” (supplement, supplemental, etc.) or “impair” (impair, impairment, etc.) or the word “auxiliary.”
Search Tool
NHTSA's Interpretation Files Search
Interpretations | Date |
---|---|
ID: nht72-2.32OpenDATE: 01/13/72 FROM: AUTHOR UNAVAILABLE; C. A. Baker for E. T. Driver; NHTSA TO: Joseph Lucas North America, Inc. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of December 23, 1971, to Mr. J. E. Leyseth of this Office in which you asked if each reflex area in a two-section reflector separated by a side marker lamp needs to meet the photometric requirements of a Class A reflector. Each reflex area need not meet the photometric requirements for a Class A reflex reflector provided that when the areas are combined they meet the photometric requirements, and provided further, that the marker lamp lens is included in the maximum exposed area of 12 sq. in. contained within a 7 in. diameter circle per SAE J594d. |
|
ID: nht72-2.33OpenDATE: 02/07/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: K-D Lamp Company TITLE: FMVSS INTERPRETATION TEXT: In your letter of January 20 to Mr. Vinson of this office you ask for an interpretation of paragraph S4.7 "Replacement Equipment" of Motor Vehicle Safety Standard No. 108. Standard No. 108 applies to motor vehicles manufactured on or after January 1, 1972. The standard specifies items with which these vehicles must be equipped. The standard also applies to items manufactured on or after January 1, 1972, intended to replace items required by Standard No. 108 to be original equipment on these vehicles. This replacement equipment must be manufactured to confirm to Standard No. 108 and certified as meeting all applicable Federal motor vehicle safety standards. The standard does not require conformance or certification of items intended as replacement equipment on vehicles manufactured before January 1, 1972. In this circumstance a manufacturer may continue to manufacture replacement equipment that does not meet Standard No. 108. |
|
ID: nht72-2.34OpenDATE: 04/13/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Amerace - Esna Corporation TITLE: FMVSS INTERPRETATION TEXT: In your letter of February 4 to Mr. Schneider you discussed differences between SAS Standard J594d, March 1957, Reflex Reflectors, and its successor J594e, March 1970. You asked "whether relief can be granted in the unnecessary specular restriction appearing in Federal Motor Vehicle Safety Standard No. 108 because of its inclusion of J594d rather than J594e." We have reviewed your letter and the administrator has determined that the issue you raised merits (Illegible Word) of rulemaking. I enclose a copy of a notice proposing an amendment to Standard No. 108 to substitute SAE J594e as the referenced requirement for reflex reflectors. |
|
ID: nht72-2.35OpenDATE: 02/15/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: D. M. Schwentker, Esq. -- Busby, Rivkin, Sherman and Levy TITLE: FMVSS INTERPRETATION TEXT: In your letter of November 30, 1971, you ask if you may assume certain statements to be true. My reply lists your statements and discusses each separately. "1. 571.5(a) applies to SAE Standards and Recommended Practices subreferenced by the SAE Standards and Recommended Practices referenced in the Federal Motor Vehicles Safety Standards contained in Part 571 as well as to the primary references. The Initial Standards incorporate many SAE materials, probably due in large part to the statutory mandate that they be based upon existing standards. The intent of 571.5(a) appears to be to insure that those materials are legitimately incorporated into the Federal requirements, and that materials subject to change are in fact "frozen" as of a day certain, so that the Federal Standards are not subject to attack on grounds of vagueness. J575 is not directly "referred to" in Standard No. 106, but since its inclusion in Standard No. 108 is required to complete the structure of the Standard, I do not regard a direct reference as necessary to bring it within the ambit of 571.5(a). The SAE Standards that are part of Standard No. 108 "refer" to J575 and this is sufficient. "2. [Materials] . . . 'in effect on the date of adoption of this Part . . . means [materials] . . . in effect on the date of publication in the Federal Register of the Federal Motor Vehicle Safety Standard or regulation in which they are referenced . . .' The answer is obviously "yes" with reference to the Initial Standards; February 3, 1967, was both the "date of adoption of this Part" as well as "the date of publication in the Federal Register of the Federal Motor Vehicle Safety Standard or regulation in which they are referenced." The answer is "no" with respect to Standards published after February 3, 1967. Section 571.5(a) says that materials subject to change incorporated in any Standard published subsequent to February 3, 1967, are those in effect on February 3, 1967, unless the reference to them provides otherwise. "3. '. . . in effect . . .' with respect to SAE Standards and Recommended Practices means formally adopted by SAE although not necessarily printed in the SAE Handbook. In the strict legal sense, an SAE Standard is never "in effect" since adherence to it is voluntary. One revision supersedes another but cannot be said legally to "revoke" it, ending its "effectivity." SAE Standards do not have effective dates. They bear an identifying month and year indicating when the latest revision was approved by the appropriate SAE approval body. Thus, J575d, November 1966, means that the (Illegible Word) was approved by the SAE lighting committee in November 1966. J575d was then printed and circulated to SAE members in January 1967, subsequently appearing in the 1968 Handbook. J575d then was "in effect" on February 3, 1967 end before appearing in the 1968 Handbook, whether considered as becoming effective upon approval by the SAE lighting committee or upon publication and distribution to SAE members. "4. SAE J575d is the revision subreferenced in Table III of Federal Motor Vehicle Safety Standard No. 108 (32 F.R. 18033) under passenger cars, tail lamps (effective January 1, 1969). Yes. Standard No. 108 was amended to adopt Table III in December 1967, based upon a proposal published on February 3, 1967. The agency did not manifest its intent, in the SPRM or any correspondence that I have been able to discover, that the referenced and subreferenced SAE Standards in the proposed standard were those appearing in the 1967 Handbook (e.g. J575c). It is a general SAE policy, however, as expressed in its Handbooks, that where revision letters are not used, the assumption is that references to Standards will designate the latest revision. Since J575d had been published and circulated in January 1967, it may be reviewed as incorporated by reference into those SAE materials referencing J575 that were part of the NPRM of February 3, 1967. I hope this answers your questions. |
|
ID: nht72-2.36OpenDATE: 12/08/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: P. F. Middleton, Esq. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of November 22, 1972 to the National Highway Traffic Safety Administration asking "whether when a school bus is being used to transport pupils, the red lights must go on when the entrance door is opened without exception." If the system is one of red lamps only, its activation according to SAE Standard J887 is not automatic but manual. The situation differs with respect to the combination amber and red lamps system. Paragraph S4.1.4(b)(ii) of Standard No. 108 effective January 1, 1972, which you reference, states "The school bus signal lamp system shall be wired so that the amber signal lamps are activated only by manual or foot operation, and if activated, are automatically deactivated and the red signal lamps automatically activated when the bus entrance door is opened." This means that the red lamps are only activated if the amber lamps have been activated before the door is opened. Activation of the red lamp system is thus dependent upon the action of the bus operator in prior activation of the amber lamp system. From the standpoint of safety we hope that his activation of the amber lamp system will be "without exception" whenever he is transporting pupils. Because paragraph S3.1.3.2 of Standard No. 108 as it was in effect from January 1, 1969 to January 1, 1972, which you also reference, could mistakenly be interpreted to require activation of the red lamp system without exception whenever the door was opened, the National Highway Traffic Safety Administration adopted the language of S4.1.4 to clarify the ambiguity.
|
|
ID: nht72-2.37OpenDATE: 07/21/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Motor Coach Industries, Inc. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of April 17, 1972, in which you requested our interpretation of several sections of Standard 121. I apologize for our delay in replying. Your first question concerns the air reservoirs which are considered to be included in the service reservoir system. As shown in your diagram, three tanks are capable of providing air to the service brake chambers: the wet air tank, the dry air tank, and the accessory tank. The first two tanks are clearly part of the service reservoir system. The accessory tank, however, has not been generally considered as part of the service brake system, and it is our opinion that it should not be included in computing the reservoir system capacity. Although the exclusion of the accessory tank from the service reservoir system would seem to weigh against the present location of your pressure gauge in the accessory system circuit, there is another feature of its operation in its present location which leads us to conclude that it would not be acceptable under the present wording of S5.1.4. In the event of a pressure loss in the accessory system (your Condition #1), the gauge would accurately indicate the pressure in the dry tank until the pressure falls to 65 p.s.i., at which point the gauge would cease to indicate the dry tank pressure and would be only an accessory tank gauge. Thus, if the check valve functions properly, the dry tank would be at 65 p.s.i. even though the gauge may read O p.s.i. Because the pressure deliverable to the brake from the service reservoir system would be the 65 p.s.i. of the dry tank, the gauge would not be indicating the service reservoir system air pressure as required by S5.1.4. Your third question is whether the vehicle must be stationary throughout the static retardation force test of S5.6.1. Our reply is that the vehicle need not remain stationary. Its friction may be overcome by the test pull, although it must exert a force of the magnitude specified in the section. Your last question relates to the treatment of trailing axles under the requirements of S5.7.1. You indicate that you presently offer an automatic emergency system as an option and that it appears inconsistent to require park brakes on each axle under the automatic application option when they are not required on each axle the other option. We are continuing our evaluation of the parking brake requirements, including the axle-by-axle braking required by S5.7.1. At this time it has not been decided whether to formally institute rulemaking to adjust the requirements. We will advise you if such rulemaking will be forthcoming. |
|
ID: nht72-2.38OpenDATE: 08/17/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Ford Motor Company TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of July 26, 1972, concerning the adjustment of a tractor's fifth wheel under the test conditions proposed in Docket 70-17, Notice 5. You state that it is not possible to load the tractor to its GVWR with the tractor's nonsteerable axles and the trailer's axles at GAWR if the fifth wheel is set in more than one position. If this is the case, and the correct loading can be obtained with the fifth wheel in one position only, then only that position will be used in compliance testing. If more than one position can be used to produce the correct loading, the tractor must conform to the requirements of the standard with the fifth wheel at any such position. |
|
ID: nht72-2.39OpenDATE: 06/13/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Lox Equipment Company TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of May 17, 1972, concerning problems you are having establishing gross axle weight ratings on vehicles you manufacture. You indicate that the problem occurs because brake drums which you use do not come with manufacturer's ratings, but are merely recommended for use with certain axles. You also ask whether a motor vehicle safety standard will require a 40-foot stopping distance from 20 mph. Your understanding that brake drum capability does not have to be considered in determining gross axle weight rating is not entirely correct. The gross axle weight rating, which is the load carrying capacity of a single axle system (49 CFR 571.3), is a measure of the safe load-carrying capacity of the entire axle system. Manufacturers should include components in their vehicles that are designed to handle loads up to these ratings. Normally an assembler can rely on the specifications or the advice of a reputable supplier as to the capacity of the supplier's components. We expect manufacturers to exercise due care in ensuring that purchased components are adequate and safe for the vehicles they are used on, in accordance with careful business practices. These do not necessarily have to take the form of formal "ratings." With reference to your question regarding stopping distance, Standard No. 121, Air Brake Systems, effective September 1, 1974 (not July 1, 1972) will, among other things, require a vehicle to stop from 20 mph in 33 and 54 feet on surfaces with skid numbers of 75 and 30 respectively. |
|
ID: nht72-2.4OpenDATE: 04/03/72 FROM: JAMES E. FORRESTER FOR ROBERT L. CARTER -- NHTSA TO: Walters Company U.S.A. TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of March 7, 1972, requesting the latest information regarding Federal Motor Vehicle Safety Standard (FMVSS) No. 301, clarification of "leakage" and comments regarding U.S. Patent No. 3, 610, 263. As amendment to FMVSS No. 301 will be issued in the near future in response to the Notice of Proposed Rule Making published earlier, 35 F.R. (Illegible Word). The substance of this action involves extending the scope of the rule as indicated in the Notice, but the details of the final amendment will not be disclosed before issue. A copy of the Notice is enclosed. Paragraph S4.4 does not mention leakage but refers to fuel spillage which is defined in S3. There is no assurance that this proposal will remain intact in the final rule since the comments from industry, continued research and development work, and many other inputs will influence the course of this rule making. We are not in a position to comment on the features of any particular device, since our concern is primarily with performance requirements in order to permit originality and choice of different means for design of improved performance. We appreciate the information about your patented fuel tank safety valve assembly, and shall place a copy of this patent in our Docket No. 70-20. This docket is a public file to receive information and comments on matters pertaining to the rule making action on fuel system integrity. We appreciate your interest in motor vehicle safety. |
|
ID: nht72-2.40OpenDATE: 07/19/72 FROM: AUTHOR UNAVAILABLE; C. A. Baker for E. T. Driver; NHTSA TO: Raybestos-Manhattan TITLE: FMVSS INTERPRETATION TEXT: In your letter of June 30, 1972, you raised two questions that touch on the responsibility of manufacturers who produce components, such as brake blocks, that affect the ability of a vehicle to meet a motor vehicle safety standard. Motor Vehicle Safety Standard No. 121, Air Brake Systems, the standard of concern to you, regulates vehicles equipped with air brakes, but it does not regulate the brakes or their components as separate items of equipment. As a component manufacturer, your company is therefore not required by our regulations to certify its products as conforming to Standard 121. This is not to say that your customers will not be concerned about the performance of your products, but only that you have no direct responsibility under the standard. A vehicle manufacturer who intends to use your brake blocks on a new vehicle will probably try to get as much test data from you as he can. His vehicle will have to conform to the standard. If our tests disclose a shortcoming in the brakes, he will have to show that he exercised due care in the manufacture of the vehicle and the data he obtains from you may be an important part of his case. Whether you supply him with dynamometer data or complete road test data is a matter to be arranged privately, however, and the subject is not regulated by our rules. A brake block or other brake component sold as a replacement part is not at this time subject to regulation under Standard 121. A truck owner will presumably want to obtain components that are compatible with the rest of the brake system. You have also asked for information about agencies equipped to run tests in accordance with Standard 121. At this time we have not compiled a list of test facilities, but we expect that such information will become widely available in the next few months. |
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.