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
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ID: aiam5222OpenMr. Han Dinh Project Manager United States Postal Service 8403 Lee Highway Merrifield, VA 22082-8101; Mr. Han Dinh Project Manager United States Postal Service 8403 Lee Highway Merrifield VA 22082-8101; "Dear Mr. Dinh: This responds to your letter requesting informatio about the conversion of postal vehicles to operate on compressed natural gas (CNG). You explained that you are deciding which specifications to apply to the CNG pressure vessels on the converted vehicles. You ask whether we would recommend the American Gas Association's voluntary standard, NGV-2, or the Department of Transportation standard for cylinders which transport CNG. By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized under the National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1381 et seq., Safety Act) to issue Federal motor vehicle safety standards that set performance requirements for new motor vehicles and items of motor vehicle equipment. NHTSA does not approve or certify any vehicles or items of equipment. Instead, the Safety Act establishes a 'self-certification' process under which each manufacturer is responsible for certifying that its products meet all applicable safety standards. NHTSA also investigates safety- related defects in motor vehicles and items of motor vehicle equipment. At present, NHTSA has not issued any standard applicable to CNG cylinders or vehicles using CNG as a fuel. However, as you know, NHTSA has undertaken rulemaking on a safety standard for CNG tanks and vehicles. (58 FR 5323, January 21, 1993.) In response to our January 1993 proposal, the agency received over 55 comments, which we are currently analyzing. We expect our next regulatory decision in early 1994. Given that this rulemaking has not been completed, NHTSA is unable to recommend to you a particular course of action with respect to the NGV-2 and DOT standards at this time. If NHTSA were to issue a safety standard for CNG cylinders and vehicles, the standard would apply to new products, and have applicability to vehicle conversions as follows. The cylinder regulation would be an equipment standard. Thus, all cylinders manufactured after the effective date of the standard would be required to comply with its requirements, whether they are placed on new vehicles or on vehicles converted to CNG fuel. The fuel system regulation would apply to new vehicles as manufactured by original equipment manufacturers or as converted prior to the first sale of the vehicle. Once the vehicle is sold, if the vehicle is converted by a commercial converter, the CNG fuel system regulation would apply if the vehicle was manufactured after the effective date of the standard and thus would have been regulated if it had originally been a CNG vehicle. With this in mind, I have enclosed a discussion that sets forth the implications under Federal law of converting gasoline-powered vehicles to use propane or other gas (such as CNG). That discussion addresses 108(a)(2)(A) of the Safety Act, which prohibits vehicle manufacturers, distributors, dealers and repair businesses from 'knowingly rendering inoperative, in whole or in part, any device or element of design installed . . . in compliance' with any FMVSS. In addition, please be aware that manufacturers of CNG tanks and vehicles are subject to the requirements in sections 151-159 of the Safety Act concerning the recall and remedy of products with defects related to motor vehicle safety. In the event that NHTSA or the manufacturer of the tank or vehicle determines that the product contains a safety- related defect, the manufacturer would be responsible for notifying purchasers of the defective equipment and remedying the problem free of charge. Our sister agency in the Department, the Federal Highway Administration (FHWA), has operational and equipment requirements for commercial vehicles used in interstate commerce. For further information about FHWA requirements, you can contact that agency's Chief Counsel's office at (202) 366-0650. I hope you find this information 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 Enclosure"; |
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ID: aiam0020OpenMr. Earl W. Kinter, Arent, Fox Kinter, Plotkin & Kahan, 1100 Federal Bar Building,1815 'H' Street, NW,Washington D.C. 20006; Mr. Earl W. Kinter Arent Fox Kinter Plotkin & Kahan 1100 Federal Bar Building 1815 'H' Street NW Washington D.C. 20006; Dear Mr. Kinter:#This is in response to your letter of April 7, 1967 in behalf of the Motor Equipment Manufacturers Association (MEMA) regarding the application of the Initial Motor Vehicle Safety Standard to original equipment and replacement parts.#I am pleased to have this opportunity to answer the questions which have been raised by the MEMA members and outlines in your letter. Before doing so, however, I would like to briefly discuss and clarify the effect of the actions taken March 29, 1967, by the National Traffic Safety Bureau, regarding Standard Nos. 111 and 206.#In your letter you have quoted certain language from the preamble to the amendments of Standards Nos. 111 to 206, and interpreted such language to mean that original equipment manufactured on or after January 1, 1968, and replacement parts for vehicles manufactured on or after that date, fall within the regulations of these two Standards. I must advise that this interpretation in not correct. These standards as now amended no longer apply to equipment, but only to the vehicles specified in the standard when such vehicles are completed by the vehicle manufacturer on or after January 1, 1968.#It should be noted that where, as in the case of amended Standard Nos. 111 and 206, the paragraph designated 'S.2' and entitled, 'Application,' refers only to vehicles and not to vehicle equipment, the person responsible for compliance is the vehicle manufacturer. This is true notwithstanding the fact that identifiable equipment may be referred to and made the subject of control in some other paragraph of the standard. For example, Standard No. 107, in paragraph S4, refers to the 'horn ring and hub of steering wheel assembly, 'and prohibits a specular gloss of the surface of such equipment from exceeding a specified brightness. The vehicle manufacturer is solely responsible for compliance with this requirement.#There are now sixteen of the twenty initial standards which require compliance only by the vehicle manufacturer. However, Standard Nos. 106,205,209 and 211 each refer to *equipment* for use in specified motor vehicles in the application paragraph. Compliance and certification is required by both equipment manufacturer and vehicle manufacturer with regard to these four standards.#I will now direct myself to your specific questions which I will quote and follow with a brief answer.#(1) Do all the Initial Standards require *compliance and certification* by parts manufactured as to *replacement parts* for vehicles manufactured *after* January 1, 1968?#Answer: No, only Standard Nos. 106,205,209 and 211. #(2) Which of the Initial Standards, if any, apply to *replacement parts* produced on or after January 1, 1968, for vehicles manufactured *prior* to that date?#Answer: Standard Nos. 106,205,209 and 211. #(3) With respect to question 2, is a certification required of the affected equipment manufacturers in such cases?#Answer: Yes. #(4) With respect to question 1-3, are the compliance and certification requirements any different where the replacement parts involved are *identical* to the original equipment for vehicles produced on or after January 1, 1968?#Answer: No. #(5)Do the Initial Standards require manufacturers of *original equipment* produced on or after January 1, 1968, to certify their products?#Answer: The requirement for certification of motor vehicle equipment found in section 114 of the National Traffic and Motor Vehicle Safety Act, provides in the pertinent part that:#>>>'Every manufacturer or distributor of ... motor vehicle equipment shall furnish to the *distributer or dealer* at the time of delivery of such ... equipment ... the certification that each such ... item of motor vehicle equipment conforms to all applicable Federal motor vehicle safety standards ...'(emphasis supplied).<< |
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ID: aiam4960OpenMr. Steve Ross Future Visions, Ltd. 28 Cherry Lane Syosset, New York 11791; Mr. Steve Ross Future Visions Ltd. 28 Cherry Lane Syosset New York 11791; "Dear Mr. Ross: This responds to your letter that requested informatio about how the laws and regulations administered by this agency would apply to a product you wish to market. This product is an antitheft device for trucks and passenger automobiles equipped with power-assisted steering. In your letter, you stated that your device is designed to prevent the theft of a vehicle by blocking the flow of hydraulic fluid in hydraulic steering systems, so that the vehicle cannot be steered. In a subsequent telephone conversation with Dorothy Nakama of my office, you explained that your device is to be installed on vehicles in the aftermarket, and will not be installed as original equipment on new vehicles. I am pleased to have the opportunity to discuss our laws and their applicability to your device. By way of background information, NHTSA has no authority to approve, endorse or offer assurances of compliance for any motor vehicle or item of motor vehicle equipment. Accordingly, it is misleading and incorrect to state, as does page 2 of the 'Summary from Originating Country' enclosed with your letter, that this device has been 'approved by the USA.' Instead, the National Traffic and Motor Vehicle Safety Act of 1966 ('Safety Act,' 15 U.S.C. 1381 et seq.) makes manufacturers of motor vehicles or items of motor vehicle equipment responsible for certifying that each of their products conforms with all applicable safety standards. In this instance, there are no specific provisions in the safety standards that set forth requirements for devices that block the flow of hydraulic fluid in hydraulic steering systems. Thus, your company as the manufacturer of such a product would not have to certify that a device that blocks the flow of hydraulic fluid in steering systems complies with any safety standards before offering it for sale to the public. However, the addition of this device to a vehicle before the vehicle's first sale to the public could affect the vehicle's compliance with the safety standards. NHTSA's certification regulation requires vehicle manufacturers to permanently attach a label to each of their new vehicles stating that the vehicle complies with all applicable safety standards. See 49 CFR 567.4. The certification regulation also sets forth requirements for persons who modify previously certified vehicles by adding, modifying, or substituting readily attachable components or who modify vehicles so that the stated weight ratings are no longer valid. Such persons are considered 'alterers' of the previously certified vehicles. Alterers are required to leave the original manufacturer's label in place and affix an additional label identifying the alterer and stating that the vehicle, as altered, continues to comply with all applicable safety standards. See 49 CFR 567.7. While your letter gave no details about how this device would be installed on a vehicle, it seems highly unlikely that a device would be treated as 'readily attachable' if it requires the installation of separate lines to carry hydraulic fluid between itself and the power steering unit. Thus, any person that installed this device on a new vehicle before the vehicle's first sale to the public would be required to certify that the vehicle complies with all applicable safety standards with this device installed. After the first sale to the public, persons who modify vehicles are subject to the prohibition in section 108(a)(2) of the Safety Act, 15 U.S.C. 1397(a)(2). That section provides that: 'No manufacturer, distributor, dealer, or motor vehicle repair business shall knowingly render inoperative, in whole or in part, any device or element of design installed on or in a motor vehicle or item of motor vehicle in compliance with an applicable Federal motor vehicle safety standard...' To avoid a 'rendering inoperative' violation for vehicles that comply with any of our safety standards, you should examine the proposed installation instructions for your device and compare those instructions with the requirements of our safety standards, to determine if installing the device in accordance with those instructions would result in the vehicle no longer complying with any of those safety standards. If the installation of your device would not result in a 'rendering inoperative' of the vehicle's compliance with the safety standards, the device can be installed by dealers, distributors, and repair shops without violating any Federal requirements. Manufacturers of motor vehicle equipment such as your device are also subject to the requirements in sections 151-159 of the Safety Act (15 U.S.C. 1411-1419) concerning the recall and remedy of products with defects related to motor vehicle safety. The Safety Act specifies that if either your company or this agency determines that a safety-related defect exists in your device, your company as the manufacturer must notify purchasers of the safety-related defect and must either: (1) repair the product so that the defect is removed, or (2) replace the product with identical or reasonably equivalent products which do not have a defect. Whichever of these options is chosen, the manufacturer must bear the full expense and cannot charge the owner for the remedy if the equipment was purchased less than 8 years before the notification campaign. For your information, I have enclosed a copy of an information sheet for new manufacturers of motor vehicles and new motor vehicle equipment. This sheet gives a brief description of our regulations and explains how to obtain copies of those regulations. You should also be aware that state laws may apply to the use of your device. For further information on state laws, you may wish to contact the American Association of Motor Vehicle Administrators at 4600 Wilson Boulevard, Arlington, Virginia 22203. I hope this information is helpful. Please feel free to contact Dorothy Nakama of my staff at this address or by telephone at (202) 366-2992 if you have any further questions or need additional information. Sincerely, Paul Jackson Rice Chief Counsel Enclosure"; |
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ID: aiam5388OpenMr. Alberto Negro Chief Executive Officer Fiat Auto R&D U.S.A. 39300 Country Club Drive Farmington Hills, MI 48331-3473; Mr. Alberto Negro Chief Executive Officer Fiat Auto R&D U.S.A. 39300 Country Club Drive Farmington Hills MI 48331-3473; Dear Mr. Negro: This responds to your letter of May 16, 1994, asking i Standard No. 208, Occupant Crash Protection 'allows the advisory information required by ... S4.5.1 to be printed in English and also in one or more foreign languages.' On March 10, 1994, NHTSA published a notice responding to petitions for reconsideration of the September 2, 1993 final rule which amended Standard No. 208 to require air bag labels (59 FR 11200). In that notice NHTSA stated: NHTSA interprets the labeling requirements of the September 2 final rule as requiring manufacturers to supply the information in English. Once this requirement is met, manufacturers may supply the same information in other languages, so long as it does not confuse consumers. As long as the non-English language label is a translation of the required information, NHTSA does not interpret it to be 'other information.' However, manufacturers are not permitted to include additional information in the non-English label. I am enclosing a copy of that notice for your information. I hope you find this information helpful. If you have any other questions, please contact Mary Versailles of my staff at this address or by phone at (202) 366-2992. Sincerely, John Womack Acting Chief Counsel Enclosure; |
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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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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.