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: aiam2536Open*AIR MAIL*#Mr. R. M. Ferrari, Chairman, Advisory Committee on Safety in Vehicle Design, Department of Transport, Box 1839Q, G.P.O., Melborne 3001, Australia; *AIR MAIL*#Mr. R. M. Ferrari Chairman Advisory Committee on Safety in Vehicle Design Department of Transport Box 1839Q G.P.O. Melborne 3001 Australia; Dear Mr. Ferrari: This is in response to your undated request (Ref. 75/1331) for a interpretation of the brake lining inspection requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 122, *Motorcycle Brake Systems*. You asked whether the brake lining wear indicator system that you described would comply with FMVSS No. 122.; Paragraph S5.1.5 requires that 'The brake system shall be installed s that the lining thickness of drum brake shoes may be visually inspected, either directly or by use of a mirror without removing the crums....' Under the system you described 'the only means of determing the lining thickness of the rear brake shoes, without removing the brake drum, is a warning lamp system which becomes energized with the lining thickness is less than 2mm.' In our opinion, this system does not comply with S5.1.5. Although the warning lamp system alerts the operator when a predetermined limit has been reached, it does not provide the direct visual means of inspection of brake lining thickness that the standard requires. Were the warning lamp system to fail, the operator would be left without a means of determining lining thickness unless he removed the brake drum.; It is anticipated that during the next year a revision of FMVSS 12 will be proposed to modify the test procedure. At that time, consideration will be given to changing the requirements of paragraph S5.1.5. These changes would reflect advances in brake wear sensor technology since the original standard was promulgated. Since the intent of of (sic) paragraph S5.1.5 is to give the driver a simple means to determine the discard limit of the friction materials, we will consider allowing other than direct means to determine this limit, provided a check of the system's function can be performed to prevent the problem mentioned above.; Sincerely, E. T. Driver, Director, Office of Crash Avoidance, Moto Vehicle Programs; |
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ID: aiam2023OpenMr. C. J. Baker, Director of Engineering, Peerless Division - Royal Industries, P.O. Box 445, Tualatin, OR 97062; Mr. C. J. Baker Director of Engineering Peerless Division - Royal Industries P.O. Box 445 Tualatin OR 97062; Dear Mr. Baker: This responds to your July 15, 1975, question whether Standard No. 121 *Air Brake Systems*, requires 'hold back valves' on air brake system reservoirs to guard against loss of air pressure through auxiliary equipment installations.; The answer to your question is no. Standard No. 121 does not contain prohibition on the use of air pressure from the air brake system for powering auxiliary devices. The vehicle must, of course, conform to Standard No. 121 following installation of the devices, if the installation occurs prior to the first purchase in good faith for purposes other than resale. For example, the compressor build-up pressure must still meet S5.1 of the standard whether or not auxiliary equipment is installed.; Although not a requirement of the standard, the NHTSA does consider i appropriate that a pressure protective valve be placed in the line to the auxiliary device so that a rupture of an auxiliary line does not cause depletion of air pressure in the brake system.; Sincerely, Frank A. Berndt, Acting Chief Counsel |
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ID: aiam2473OpenMr. William H. Tucker, Tucker, Gray and Thigpen, 2728 Eighth Street, P. O. Box 2485, Tuscaloosa, AL 35401; Mr. William H. Tucker Tucker Gray and Thigpen 2728 Eighth Street P. O. Box 2485 Tuscaloosa AL 35401; Dear Mr. Tucker: This is in reply to your letter of October 4, 1976, requesting data o the Gateway Gumbo Wide Mudder tire involved in an automobile accident that you are investigating.; From your correspondence, you indicate that the tire was manufacture by the Denman Rubber Company and that Dunlap Kyle of Batesville, Mississippi owns the engineering specifications or blueprints. As this statement suggests a variation from usual tire industry practice, we did some investigating of our records. Our records indicate that there is a retreading plant operated by Dunlap and Kyle Company, P. O. Box 689, Batesville, Mississippi, for the retreading of light truck- type tires. Therefore, before we can answer your letter, we need some additional information.; Please forward to us the tire identification number of the tire as thi will help determine if, in fact, this is a retreaded tire. This number will be located near the symbol DOT, and if it is a retreaded tire, should be located near the shoulder of the tire and not near the bead.; Sincerely, E. T. Driver, Director, Office of Crash Avoidance, Moto Vehicle Program; |
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ID: aiam2189OpenMr. Lewis Coffey, Chief Engineer, Gillig Brothers School Bus Co., 25800 Clawinter Rd., Hayward, CA 94540; Mr. Lewis Coffey Chief Engineer Gillig Brothers School Bus Co. 25800 Clawinter Rd. Hayward CA 94540; Dear Mr. Coffey: This is in response to your request for information concerning method of ensuring the compliance of school buses with the barrier crash test requirements of Federal Motor Vehicle Safety Standard No. 301-75, *Fuel System Integrity*.; Standard No. 301-75, while establishing minimum performance levels does not specify any particular design requirements for school bus fuel systems. A manufacturer is free to design his vehicles in the manner that he believes most appropriate to ensure compliance. To this end, you may find helpful information in a study by Dynamic Science entitled *School Bus Safety Improvement Program*. The NHTSA cannot assure you, however, that following the suggestions contained in the study will guarantee that your school buses will comply with the standard.; The study is filed in the NHTSA's public docket as document numbe 75-03-GR1. Copies may be obtained by writing to:>>>Technical Reference Branch, National Highway Traffic Safety Administration, Room 5108, 400 Seventh Street, S.W., Washington D.C. 20590<<<; You should refer to the following publication numbers: HS 801-615 -616, and -617.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam2920OpenMr. Sheldon C. Brooks, Marque Motors, 8711 Lyndale Ave., So., Bloomington, MN 55420; Mr. Sheldon C. Brooks Marque Motors 8711 Lyndale Ave. So. Bloomington MN 55420; Dear Mr. Brooks: This is in response to your letter of December 4, 1978, requesting a exemption from the requirements of Part 581, *Bumper Standard*, (49 CFR 581), for ten Lamborghini Countach vehicles currently under construction. You state that the Lamborghini Company's small size and difficult economic situation preclude immediate redesign of the Countach model to bring it into compliance with the bumper regulation.; Federal Motor Vehicle Safety Standard Number 215, *Exterior Protection (49 CFR 571.215), from which Lamborghini had been granted an exemption, was issued under the authority of the National Traffic and Motor Vehicle Safety Act of 1966 (Safety Act). Section 123 of the Safety Act permits the exemption of motor vehicles from safety standard when compliance would cause a manufacturer substantial economic hardship and the manufacturer has attempted in good faith to comply (15 U.S.C. 1410). Standard No. 215 was revoked effective September 1, 1978.; The present bumper regulation, Part 581, effective September 1, 1978 was issued under Title I of the Motor Vehicle Information and Cost Savings Act (Cost Savings Act) (15 U.S.C. 1901), which permits exemptions only for passenger motor vehicles manufactured for a special use. In view of the narrowness of this statutory provision, the National Highway Traffic Safety Administration has no authority to grant an exemption from Part 581 on the basis of economic hardship or limited production.; Part 581 applies to passenger motor vehicles, other than multipurpos vehicles, manufactured on or after September 1, 1978 (49 CFR 581.5(a)). Therefore, vehicles manufactured by Lamborghini which are completed after August 31, 1978, must meet the requirements of the regulation, if they are imported into or sold in the United States.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam3632OpenMr. Richard M. Kleber, Engineering Manager, Performance Vehicles, Inc., 19747 Wolf Road, Mokena, IL 60448; Mr. Richard M. Kleber Engineering Manager Performance Vehicles Inc. 19747 Wolf Road Mokena IL 60448; Dear Mr. Kleber: This is in reply to your letter of November 15, 1982, to Mr. Fairchil of this office, asking how the National Highway Traffic Safety Administration classifies the 'Trihawk' three-wheeled motor vehicle for purposes of the Federal motor vehicle safety standards and other regulations.; The National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1381 e seq.) defines a motor vehicle, in pertinent part, as 'any vehicle driven or drawn by mechanical power manufactured primarily for use on the public streets, roads, and highways....' (1391(3)). From the brochure you enclosed, the Trihawk appears to be manufactured for use on the public roads and, hence, is subject to the Federal safety standards, and to other regulations such as those requiring notification and remedy in the event the vehicle fails to comply with any applicable safety standard or incorporates a safety-related defect (1411 et seq.).; Agency regulations (49 CFR Part 571.3(b)) define a 'motorcycle' as ' motor vehicle with motive power having a seat or saddle for the use of the rider and designed to travel on not more than three wheels in contact with the ground.' The standards applicable to 'motorcycles,' therefore, are those that the three-wheeled Trihawk must meet.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3262OpenMr. Nicholas M. Stefano, Manager, Mechanical Device Development Advanced Systems Engineering, TRW, Inc., Building E2, Room 4062, One Space Park, Redondo Beach, California 90278; Mr. Nicholas M. Stefano Manager Mechanical Device Development Advanced Systems Engineering TRW Inc. Building E2 Room 4062 One Space Park Redondo Beach California 90278; Dear Mr. Stefano: This responds to your letter of January 7, 1980, in which you describ an automotive, electronic display device being designed by TRW and asked for a legal opinion as to its potential compliance with Federal Motor Vehicle Safety Standard No. 127, *Speedometers and Odometers*. You noted that, upon installation in a motor vehicle, TRW's device would continuously display vehicle and engine speed readings in the form of a bargraph. In potentially hazardous situations requiring the driver to take extra caution or to shut down the vehicle's engine, the TRW device would intermittently interrupt the display of vehicle and engine speeds with sequences of verbal messages. In light of this, you asked whether the fact that TRW's device would not display the vehicle speed during every moment of vehicle operation would prevent it from complying with Safety Standard No. 127.; Based on our understanding of your design, it appears that alternatin the display of speed and verbal messages would not violate the standard. Although the future development of electronic digital speedometers was considered in the development of Safety Standard No. 127, the specific type of device described in your letter was not contemplated. The agency had expected that all speedometers would continuously display vehicle speed. While the intermittent display feature would apparently not violate Safety Standard No. 127 as it is now written, we are concerned about the possible adverse impact upon traffic safety that this feature might have. In particular, we have in mind the effects of a driver's(sic) being unable to determine vehicle speed when he or she is approaching or negotiating a curve or exit ramp. Rapid deceleration to a particular speed is typically necessary in such situations.; In the case of a speedometer which periodically does not displa vehicle speed for periods of 5 seconds, a vehicle traveling at 55 mph would cover approximately 400 feet in that interval and a vehicle traveling at 40 mph, approximately 300 feet. Although your alternative mode of operation would reduce this interval through flashing the speed for periods of 0.10 seconds, we question whether such a short period would be sufficient to enable drivers to read their speedometers. We solicit any test or research that TRW has done on the safety side effects of your design. A member of the agency's accident avoidance division will contact you to discuss this issue further.; In looking at your design, we noted several aspects of it that woul apparently not comply with Safety Standard No. 127. The design does not appear to be graduated in both miles and kilometers per hour as required by section 4.1.2. Further, the design neither has the numeral 55 nor highlights either that numeral of the point at which vehicle speed equals 55 mph as required by section 4.1.5.; Finally, I would emphasize that this letter represents only th agency's opinion based on the information supplied in your letter. The NHTSA does not formally render judgement on the compliance of any vehicle or equipment design with any safety standard before the manufacturer's certification of its product. It is the manufacturer's responsibility under the law to determine whether its vehicle or equipment comply with all applicable safety standards and regulations and to certify its vehicles in accordance with that determination.; I hope that your will find this response helpful and have not bee inconvenienced by our delay in sending it to your.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3798OpenRichard W. Janney, Captain, Commander, A.S.E.D., Maryland State Police, 6601 Ritchie Highway, Glen Burnie, MD 21062; Richard W. Janney Captain Commander A.S.E.D. Maryland State Police 6601 Ritchie Highway Glen Burnie MD 21062; Dear Captain Janney: This is to follow-up your phone conversation with Stephen Oesch, of m staff concerning the agency's letter of December 20, 1983, on Standard No. 205, *Glazing Materials*. I hope that the following discussion will clarify the relationship between the requirements of Standard No. 205 and the render inoperative provision of the National Traffic and Motor Vehicle Safety Act (the Act).; Section 108(a)(2)(A) of the Act prohibits motor vehicle manufacturers distributors, dealers, and motor vehicle repair shops from knowingly rendering inoperative any device or element of design installed in compliance with a Federal motor vehicle safety standard. Standard No. 205 sets performance requirements, including requirements for light transmittance and abrasion resistance, for all glazing materials used in motor vehicles. Those performance requirements may vary depending on the vehicle type involved and the place in the vehicle where the glazing is used. For example, the luminous transmittance and abrasion resistance requirements apply to all windows in a passenger car, but only to windshield and windows to the immediate right and left of the driver in a truck or multipurpose passenger vehicle.; The application of tinting materials to glazing does not, in and o itself, constitute a violation of the render inoperative provision of section 108(a)(2)(A) of the Act. To violate section 108(a)(2)(A), manufacturers, distributors, dealers, and motor vehicle repair shops that install tinting materials must knowingly install materials which render inoperative the glazing material's compliance with Standard No. 205. Thus, for example, a motor vehicle repair shop would be in violation of section 108(a)(2)(A) of the Act if it knowingly installed in a passenger car a tinting material which would render inoperative the glazing's compliance with the abrasion resistance requirements of the standard. In each case, there will be a factual question of whether the glazing material, as tinted, will continue to meet the abrasion resistance requirements of the standard.; If you are aware of any manufacturers, distributors, dealers, or moto vehicle repair shops that are in apparent violation of section 108(a)(2)(A), please provide information concerning those apparent violations to our Office of Vehicle Safety Compliance. The information should be sent to:; >>>Mr. Francis Armstrong, Director Office of Vehicle Safety Compliance National Highway Traffic Safety Administration Room 6113 400 Seventh Street,S.W. Washington, D.C. 20590<<< I hope this discussion will be of assistance to you. If you have an further questions, please let me know.; Sincerely, Frank BErndt, Chief Counsel |
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ID: aiam4773OpenHerr Hanno Westermann Hella KG Hueck & Co Postfach 28 40 4780 Lippstadt W. Germany; Herr Hanno Westermann Hella KG Hueck & Co Postfach 28 40 4780 Lippstadt W. Germany; Dear Herr Westermann: This is in reply to your letter to Dr. Burgett o this agency with respect to 'multi bulb devices', specifically 'how the requirements for one-, two-, or three compartment lamps (lighted sections) as it is documented in FMVSS No. 108, Figure lb have to be interpreted. . . .' You have asked this question because 'Hella would like to equip motor vehicles with signalling devices which have --opposite to conventional lamps--a great number of replaceable miniature bulbs instead of e.g. one 32 cp bulb.' Your question assumes that Standard No. 108 is to be interpreted in a manner that equates the number of lighted sections with the number of bulbs providing the light. Finally, you have stated that the total area of the lamp is not larger than current one-compartment lamps. We regret the delay in responding to your letter, but we have recently completed rulemaking, begun in September l988, which is relevant to your question. On May 15, l990, an amendment to Standard No. 108 was published, effective December 1, l990, the effect of which is to restrict Figure 1b to replacement equipment. I enclose a copy of the amendment for your information. Your question relates to 'signalling devices' for new motor vehicles, and Figure 1b shows that, specifically, you refer to turn signal lamps. Beginning December l, l990, Standard No. 108 will specify two different standards for turn signal lamps. If the lamp is intended for use on multipurpose passenger vehicles, trucks, buses, and trailers whose overall width is 80 inches or more, it must be designed to conform to SAE Standard J1395 APR85 Turn Signal Lamps for Use on Motor Vehicles 2032 mm or More in Overall Width. SAE J1395 also provides that these lamps may be used on vehicles less than this width, except for passenger cars. If a motor vehicle is not equipped with a turn signal lamp designed to conform to SAE J1395, it must be equipped with a turn signal lamp designed to conform to SAE Standard J588 NOV84 Turn Signal Lamps for Use on Motor Vehicles Less Than 2032 mm in Overall Width. In the May l990 amendments, section S3 of Standard No. 108 was amended to add a definition for 'Multiple Compartment Lamp'. Such a lamp is 'a device which gives its indication by two or more separately lighted areas which are joined by one or more common parts, such as a housing or lens.' The multiple bulb device that you described appears to meet this definition. SAE J1395 establishes luminous intensity minima and maxima photometric requirements without reference to either compartments or lighted sections, and all that is required is for the lamp to comply at the individual test points specified. New section S5.1.1.31 clarifies that measurements of a multiple compartment turn signal lamp on vehicles to which SAE J1395 applies are to made for the entire lamp and not for the individual compartments. However, SAE J588 NOV84 continues to specify different minimum photometric requirements for one, two, and three 'lighted sections'. Because the SAE does not prescribe photometric requirements for more than three lighted sections, we have concluded that any device that contains more than three lighted sections need only comply with the requirements prescribed for three lighted sections. I hope that this is responsive to your request. Sincerely, Paul Jackson Rice Chief Counsel; |
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ID: aiam1571OpenMr. John H. Mueller,The Weatherhead Company,300 East 131st Street,Cleveland, Ohio 44108; Mr. John H. Mueller The Weatherhead Company 300 East 131st Street Cleveland Ohio 44108; Dear Mr. Mueller:#This responds to your July 10, 1974, request t modify the hose labeling provisions of Standard No. 106-74, *Brake hoses*, to permit DOT labeling of 1/8-inch O.D. nylon tubing.#To the best of our knowledge 1/8-inch O.D. tubing is not used as brake hose as it is defined by the standard:#>>>'Brake hose' means a flexible conduit manufactured for use in a brake system to transmit or contain the fluid pressure or vacuum used to apply force to a vehicle's brakes'<<<#The tubing is used for pressure gauge lines and in two-speed differentials, but is apparently not used to transmit or contain the pressure used to apply force to a vehicle's brakes. As it is not considered to be brake hose under the standard, it should not be labeled with the DOT symbol.#Aside from this prohibition on the use of the DOT symbol, you are free to label 1/8-inch O.D. nylon tubing as you choose.#Yours truly,Richard B. Dyson,Acting 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.