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: aiam4304OpenMr. Goro Utsunomiya, Branch Manager, Mazda, Toyo Kogyo U.S.A. Representative Office, 1444 McGaw Avenue, Irvine, CA 92705; Mr. Goro Utsunomiya Branch Manager Mazda Toyo Kogyo U.S.A. Representative Office 1444 McGaw Avenue Irvine CA 92705; Dear Mr. Utsunomiya: This is in response to your letter of May 9, 1974, requesting a interpretation of the test procedure specified in Standard No. 301 (Docket No. 73-20, Notice 2) concerning the operation of the vehicle's fuel pump during testing.; Paragraph S7.1.3 of the standard requires that electrically driven fue pumps be in operation during the barrier crash tests if they normally operate with the activation of the vehicle's electrical system. If the pump is incapable of functioning with the independent activation of the electrical system and requires the operation of the vehicle's engine, then the pump should not be running during the barrier crash tests.; Based upon the description you provide in your letter, it appears tha you should conduct your barrier crash testing without operating the fuel pump.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam5570OpenMr. Doug Russel Design Engineer Advance Engineered Products 144 Henderson Drive Regina, Saskatchewan S4V 2B2; Mr. Doug Russel Design Engineer Advance Engineered Products 144 Henderson Drive Regina Saskatchewan S4V 2B2; Dear Mr. Russel: This responds to your letter asking about the brak power requirements in section S5.4.2 of Federal motor vehicle safety standard No. 121, Air Brake Systems (49 CFR 571.121). You asked whether there are any limitations on the pressure which can be used to achieve the required deceleration rate specified in S5.4.2.2. As explained below, the same limitation on the pressure which can be used to achieve the deceleration rate specified in S5.4.2.1 applies to the deceleration in S5.4.2.2. You also asked whether brakes must be capable of meeting the specific deceleration rate specified in S5.4.2.2. The answer to that question is yes. Some background information on Federal motor vehicle safety laws and regulations may be helpful. Congress has authorized this agency the National Highway Traffic Safety Administration (NHTSA), to issue Federal motor vehicle safety standards applicable to new motor vehicles and new items of motor vehicle equipment. NHTSA has used this authority to establish Standard No. 121, which applies to braking systems on vehicles equipped with air brakes. The agency, however, does not approve motor vehicle or motor vehicle equipment, nor does it endorse any commercial products. Instead, Congress has established a 'self-certification' process under which each manufacturer is responsible for certifying that its products meet all applicable safety standards. Standard No. 121's brake power requirements are set forth in section S5.4.2. The purpose of these requirements is to help ensure that brakes retain adequate stopping capability during and after exposure to prolonged or severe use, such as long, downhill driving. The brake power procedure specified by that section is conducted on a dynamometer and is intended to replicate real world brake performance. The specified decelerations are designed to heat the brakes to simulate severe driving conditions. Section S5.4.2 requires that each brake shall be capable of making 10 consecutive decelerations at an average rate of 9 f.p.s.p.s from 50 m.p.h. to 15 m.p.h., at equal intervals of 72 seconds, and shall be capable of decelerating to a stop from 20 m.p.h. at an average deceleration rate of 14 f.p.s.p.s. 1 minute after the 10th deceleration. For the first ten decelerations, section S5.4.2.1 specifies the conditions under which the decelerations must be performed, including that 'The service line air pressure shall not exceed 100 p.s.i. during any deceleration.' For the eleventh deceleration, S5.4.2.2 specifies that 'one minute after the end of the last deceleration required by S5.4.2.1 and with the drum or disc rotating at a speed of 20 m.p.h., decelerate to a stop at an average deceleration rate of 14 f.p.s.p.s.' In asking whether there are any limitations on the pressure which can be used to achieve this eleventh deceleration, you noted that S5.4.2.2, unlike S5.4.2.1, does not explicitly specify a pressure limitation. However, reading section S5.4.2 (including S5.4.2.1 and S5.4.2.2) as a whole, the brake line pressure limitation set forth in S5.4.2.1 applies to the eleventh deceleration as well. Section S5.4.2 specifies a test procedure consisting of a series of events, i.e., preparing the dynamometer for the test including a 100 p.s.i. pressure limit, then making 10 decelerations on the dynamometer under the conditions set forth in S5.4.2.1, then making the eleventh deceleration. Section S5.4.2.2 does not specify any change in the dynamometer pressure limit for the eleventh deceleration. The dynamometer pressure limit specified for the brake power test simply reflects the fact that tractor trailer brakes are typically configured to operate at a maximum nominal brake pressure of approximately 100 psi. Use of a higher brake pressure that differed from a vehicle's actual maximum brake pressure would result in the brake power test not being representative of real world brake performance. In response to your second question, section S5.4.2 specifies that a brake must be capable of decelerating to a stop from 20 m.p.h. at an average deceleration rate of 14 f.p.s.p.s. 1 minute after the 10th deceleration. See also S5.4.2.2. A brake which could not achieve this specified deceleration rate for the eleventh deceleration would not comply with the Standard's requirements. I hope this information has been helpful. If you have any other questions, please contact Marvin Shaw of my staff at this address or by phone at (202) 366-2992. Sincerely, John Womack Acting Chief Counsel; |
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ID: aiam0261OpenMr. Gerald Sagerman, U.S. Agent, TVR Engineering, Ltd., 572 Merrick Road, Lynbrook, NY 11563; Mr. Gerald Sagerman U.S. Agent TVR Engineering Ltd. 572 Merrick Road Lynbrook NY 11563; Dear Mr. Sagerman: This is in response to your letter of October 14, 1970, to the Directo of the National Highway Safety Bureau forwarding information sheets on the TVR Vixen. I am enclosing copies of the Bureau's Consumer Information Regulations (49 CFR Part 575). The substantive provisions, S 575.101 on vehicle stopping distance, S 575.102 on tire reserve load, and S 575.106 on acceleration and passing ability, require the furnishing of specific information in a format which is in the form set out in the regulations. The information sheets which you have provided fall short of these requirements in both form and substance. For example, S 575.101 requires furnishing information on the minimum stopping distance, expressed in feet, for the particular vehicle, from a particular speed, at specified loads, with the braking system in a specified condition. The information provided by you in this regard is incomplete, and is not in the form specified. In addition, the regulations require the information to describe and be valid for each of the vehicles with which it is provided.; Please study the enclosed regulations carefully and forward to u complying consumer information within the near future. Let us know if you need further assistance.; Sincerely, Rodolfo A. Diaz, Acting Associate Director, Motor Vehicl Programs; |
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ID: aiam0262OpenMr. Gerald Sagerman, U.S. Agent, TVR Engineering, Ltd., 572 Merrick Road, Lynbrook, NY 11563; Mr. Gerald Sagerman U.S. Agent TVR Engineering Ltd. 572 Merrick Road Lynbrook NY 11563; Dear Mr. Sagerman: This is in response to your letter of October 14, 1970, to the Directo of the National Highway Safety Bureau forwarding information sheets on the TVR Vixen. I am enclosing copies of the Bureau's Consumer Information Regulations (49 CFR Part 575). The substantive provisions, S 575.101 on vehicle stopping distance, S 575.102 on tire reserve load, and S 575.106 on acceleration and passing ability, require the furnishing of specific information in a format which is in the form set out in the regulations. The information sheets which you have provided fall short of these requirements in both form and substance. For example, S 575.101 requires furnishing information on the minimum stopping distance, expressed in feet, for the particular vehicle, from a particular speed, at specified loads, with the braking system in a specified condition. The information provided by you in this regard is incomplete, and is not in the form specified. In addition, the regulations require the information to describe and be valid for each of the vehicles with which it is provided.; Please study the enclosed regulations carefully and forward to u complying consumer information within the near future. Let us know if you need further assistance.; Sincerely, Rodolfo A. Diaz, Acting Associate Director, Motor Vehicl Programs; |
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ID: aiam2789OpenMr. Eduardo A. Santiago, 1137 Barium Road, Modesto, CA 95351; Mr. Eduardo A. Santiago 1137 Barium Road Modesto CA 95351; Dear Mr. Santiago: This responds to Raycor Industries' March 13, 1978, question whethe Standard No. 121, *Air Brake Systems*. applies to an air dryer that is installed in the air brake system of trucks that must comply with the standard.; The answer to your question is no. Paragraph S3 (Applicability) o Standard No. 121 states that the standard applies to trucks, buses, and trailers equipped with air brake systems (with some specified exceptions). The standard therefore applies only to vehicles, and does not apply to motor vehicle equipment such as the Raycor air dryer unit. The vehicles in question must, of course, conform to Standard No. 121 following installation of the device, if the installation occurs prior to the first purchase in good faith for purposes other than resale.; A copy of Standard No. 121 is enclosed for your information. Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam4486OpenW.E. Baldwin, Ph.D. President, K-R Industries 418 Crestwood Avenue Feasterville, PA 19047; W.E. Baldwin Ph.D. President K-R Industries 418 Crestwood Avenue Feasterville PA 19047; Dear Dr. Baldwin: This is in reply to your letter of September 1, 1988 asking for an interpretation of paragraph S4.5.11(e) of Motor Vehicle Safety Standard No. 108. You have developed a center highmounted stop lamp 'containing 5 bulbs, where each bulb is illuminated in sequential order.' You state that the 'time between each lamp illumination is less than 250 ms, providing a steady photometric value, meeting S4.1.1.41(c)', and that 'the red lens of the lamp is steadily illuminated, with the illuminated area moveing (sic) in a back and forth motion.' In your opinion, the invention meets the requirement of S4.5.11(e) that lamps, other than those enumerated, be steady-burning. We cannot provide the interpretation you seek. Under paragraph S4.5.4, 'the stop lamps on each vehicle shall be activated upon activation of the service brakes.' This means that all bulbs providing the center stop lamp signal must be simultaneously activated, not sequentially. In addition, we do not consider a lamp with a moving illuminated area to be one that is steady-burning within the meaning to S4.5.11(e). Sincerely, Erika Z. Jones Chief Counsel; |
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ID: aiam3686OpenMr. J. N. Uranga, Cummins Engine Company, Inc., Box 3005, Columbus, IN 47201; Mr. J. N. Uranga Cummins Engine Company Inc. Box 3005 Columbus IN 47201; Dear Mr. Uranga: This is in further response to your January 28, 1983, letter in whic you asked about the defect reporting requirements in Part 573, *Defect and Noncompliance Reports*. We responded by letter to you on March 24 indicating that as an original equipment manufacturer you might have some reporting responsibilities if a component of your original equipment was found to be defective.; In a conversation with Roger Tilton of my staff, you have indicate that you manufacture the engine of a certain vehicle and another manufacturer produces the fan. Both pieces of equipment are then sent to the vehicle manufacturer for assembly with the vehicle. In this instance, you ask whether you would have reporting responsibilities if the fan were determined to be defective. The answer to your question is no.; In the situation that you pose, you do not install the fan on you equipment nor does the fan ever come within your control. Therefore, you would not have responsibility for that part. The fan manufacturer and the vehicle manufacturer would be responsible for any defects in that equipment. In instances where you might install a fan on your equipment prior to sale to the vehicle manufacturer, you might have reporting responsibilities if a defect is discovered in that part, since the part would be a component of the overall engine that you supplied to the vehicle manufacturer.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3687OpenMr. J. N. Uranga, Cummins Engine Company, Inc., Box 3005, Columbus, IN 47201; Mr. J. N. Uranga Cummins Engine Company Inc. Box 3005 Columbus IN 47201; Dear Mr. Uranga: This is in further response to your January 28, 1983, letter in whic you asked about the defect reporting requirements in Part 573, *Defect and Noncompliance Reports*. We responded by letter to you on March 24 indicating that as an original equipment manufacturer you might have some reporting responsibilities if a component of your original equipment was found to be defective.; In a conversation with Roger Tilton of my staff, you have indicate that you manufacture the engine of a certain vehicle and another manufacturer produces the fan. Both pieces of equipment are then sent to the vehicle manufacturer for assembly with the vehicle. In this instance, you ask whether you would have reporting responsibilities if the fan were determined to be defective. The answer to your question is no.; In the situation that you pose, you do not install the fan on you equipment nor does the fan ever come within your control. Therefore, you would not have responsibility for that part. The fan manufacturer and the vehicle manufacturer would be responsible for any defects in that equipment. In instances where you might install a fan on your equipment prior to sale to the vehicle manufacturer, you might have reporting responsibilities if a defect is discovered in that part, since the part would be a component of the overall engine that you supplied to the vehicle manufacturer.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3810OpenMr. Louis Lemmens, Decoba N.V., 3500 Hasselt, Vaarstraat 4, Belgium; Mr. Louis Lemmens Decoba N.V. 3500 Hasselt Vaarstraat 4 Belgium; Dear Mr. Lemmens: This responds to your letter to this office seeking information o requirements applicable to retreaded truck tires imported into the United States. Specifically, you asked whether a foreign-based retreader would be required to put another tire identification number on the tires it retreads, or whether that retreader could simply leave the original manufacturer's identification number on the retreaded tire. As explained below, the retreader is required to mark its own tire identification number on each tire it retreads. You then asked for information on how a retreader obtains an identification number, and this procedure is set forth below.; For your information, I have enclosed a copy of 49 CFR Part 574, *Tir Identification and Recordkeeping*. Section 574.5 specifies that *each* tire retreader shall permanently label one sidewall of *each* tire he retreads with the information specified in that section. For a retreader, the first group of three symbols in the identification number would represent the retreader's assigned identification mark, the second group of two symbols would identify the retread matrix in which the tire was processed, the third group of four symbols may be used to identify characteristics of the tire at the retreader's option, and the fourth group of three symbols would identify the week and year in which the tire was retreaded.; Section 574.6 explains the procedures to be followed by the retreade in applying for an identification mark, and specifies the information which must be provided by the retreader. The agency usually assigns the identification mark within two weeks of receiving the necessary information from a retreader.; However, a retreader identification mark will not be assigned until th retreader has designated an agent for the service of process, according to the requirements of 49 CFR S551.45 (copy enclosed). That section specifies that, for a designation of agent to be valid, it must contain the following six items:; 1. A certification that the designation is valid in form and binding o the retreader under the laws, corporate by-laws, or other requirements governing the making of the designation at the time and place where it is made,; 2. The full legal name, principal place of business, and mailin address of the retreader,; 3. Marks, trade names, or other designations of origin of any of th retreader's products which do not bear his name,; 4. A statement that the designation shall remain in effect unti withdrawn or replaced by the manufacturer,; 5. A declaration of acceptance duly signed by the agent appointed which may be an individual, a firm, or a U.S. corporation, and; 6. The full legal name and address of the designated agent. In addition, the designation must be signed by one with authority t appoint the agent, and the signer's name and title should be clearly indicated beneath his signature. This designation should be mailed to the address shown in S551.45(b). When this agency has received both a completed application for a retreader identification mark and a designation of agent, a code mark will be assigned to the retreader promptly. This identification mark will be sent directly to the retreader and not to the designated agent.; Please feel free to contact me should you need any further informatio in this matter.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam2802OpenMr. Marsh Pottorff, Potts Motorcycle Company, 717 4th, Pueblo, CO 81001; Mr. Marsh Pottorff Potts Motorcycle Company 717 4th Pueblo CO 81001; Dear Mr. Pottorff: This responds to your February 11, 1978, letter asking whether a devic manufactured by you which is designed to tow motorcycles behind a motor vehicle would be considered a trailer.; The term trailer is defined in Part 571.3 of Volume 49 of the Code o Federal Regulations to mean 'a motor vehicle with or without motive power, designed for carrying persons or property and for being drawn by another motor vehicle.' Since your device falls within the ambit of this definition, it is considered a trailer and must comply with all of the Federal motor vehicle safety standards applicable to that vehicle type.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
Request an Interpretation
You may email your request to Interpretations.NHTSA@dot.gov or send your request in hard copy to:
The Chief Counsel
National Highway Traffic Safety Administration, W41-326
U.S. Department of Transportation
1200 New Jersey Avenue SE
Washington, DC 20590
If you want to talk to someone at NHTSA about what a request for interpretation should include, call the Office of the Chief Counsel at 202-366-2992.
Please note that NHTSA’s response will be made available in this online database, and that the incoming interpretation request may also be made publicly available.