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: aiam4812OpenMs. Rebecca Flint Polymeric Systems, Inc. Wheatland and Mason Streets Phoenixville, PA 19460; Ms. Rebecca Flint Polymeric Systems Inc. Wheatland and Mason Streets Phoenixville PA 19460; "Dear Ms. Flint: This responds to your letter asking whether thi agency must approve your product, an epoxy putty that could be used to repair leaking gas tanks. You said a customer would like to market your product 'for fleet (buses and truck) maintenance.' The answer is no, the National Highway Traffic Safety Administration (NHTSA) does not approve or certify products. By way of background, NHTSA is authorized to issue Federal Motor Vehicle Safety Standards (FMVSS's) applying to the manufacture of new motor vehicles and items of motor vehicle equipment. NHTSA is not authorized to certify or approve motor vehicles or motor vehicle equipment for compliance with our FMVSS's. Instead, under the National Traffic and Motor Vehicle Safety Act (copy enclosed), each manufacturer of a motor vehicle or item of motor vehicle equipment is responsible for certifying that its products meet all of our applicable safety standards. This process requires each manufacturer to determine in the exercise of due care that its products meet all applicable requirements. NHTSA regularly tests vehicles and equipment for compliance with the FMVSS's as part of its enforcement program. In addition, the agency also investigates safety-related defects in motor vehicles and items of motor vehicle equipment. There isn't any FMVSS that directly applies to repair putty for fuel tanks. Federal Motor Vehicle Safety Standard 301, Fuel System Integrity, sets performance requirements for new vehicles with a gross vehicle weight rating of 10,000 pounds or less and school buses. The standard does not apply to products sold to repair fuel tanks on vehicles already in use. Repair of a damaged fuel tank in a new vehicle would be affected by the statutory requirement that the vehicle, when first sold to a consumer, must comply with FMVSS 301. If a new vehicle's fuel tank is repaired prior to such sale, the person making the repairs would be considered a vehicle alterer under our regulation on certification (Part 567, copy enclosed). As an alterer, the person must certify that the fuel system, as altered, continues to comply with all of the applicable requirements of Standard 301. After a vehicle is first sold to a consumer, repairs to a vehicle are potentially affected by section 108(a)(2)(A) of the Vehicle Safety Act. That section prohibits manufacturers, distributors, dealers, or motor vehicle repair businesses from knowingly rendering inoperative any device or element of design installed in compliance with a FMVSS. However, the agency does not view that prohibition as applying to the repair of a fuel tank which has been previously installed in a vehicle and damaged in use. The agency considers the event that damaged the fuel tank and not any subsequent action by a person repairing the damaged tank in a used vehicle as the event that 'rendered inoperative' the compliance of the fuel tank with the standard. Thus, a person in one of the aforementioned categories may use the putty to repair a damaged fuel tank on a used vehicle without regard to the render inoperative prohibition. Of course, however, NHTSA urges all persons repairing motor vehicles to ensure that the repair is done safely. The prohibition of section 108(a)(2)(A) does not apply to individual vehicle owners who alter their own vehicles. Thus, under our requirements, individual owners may use the repair putty regardless of its effect on the performance of fuel tanks. However, NHTSA encourages vehicle owners not to tamper with vehicle safety equipment if the modification would degrade the safety of the vehicle. An issue raised by your inquiry is whether the putty is 'motor vehicle equipment' under the Vehicle Safety Act. Manufacturers of motor vehicle equipment are subject to the requirements in sections 151-159 of the Safety Act concerning the recall and remedy of products with defects relating to motor vehicle safety. As discussed below, we believe the putty is not motor vehicle equipment. Section 103(4) of the Act defines, in relevant part, the term 'motor vehicle equipment' as: any system, part, or component of a motor vehicle as originally manufactured or any similar part or component manufactured or sold for replacement or improvement of such system, part, or component or as any accessory, or addition to the motor vehicle . . . (emphasis added). In determining whether an item of equipment is considered an 'accessory . . . to the motor vehicle,' NHTSA applies not only the relevant statutory language, but also two criteria. The first criterion is whether a substantial portion of the expected uses of the item are related to the operation or maintenance of motor vehicles. We determine the expected uses by considering product advertising, product labeling, and the type of store that retails the product, as well as available information about the actual use of the product. The second criterion is whether the product is intended to be used principally by ordinary users of motor vehicles (e.g., items normally used by professional vehicle repair and maintenance personnel would not qualify). If the product satifies both criteria, the product is considered to be an 'accessory' and thus is subject to the provisions of the Safety Act. Applying these criteria to your inquiry, the first criterion appears to be satisfied because a substantial portion of the expected uses of the putty is related to the operation or maintenance of motor vehicles. The second criterion, however, does not appear to be satisfied. In a December 21, 1990 telephone conversation with Ms. Fujita of my staff, you stated that the putty would be sold to professional mechanics only. Since your product is not intended for use by ordinary vehicle users, the putty is not considered to be motor vehicle equipment. Our sister agency in the Department, the Federal Highway Administration (FHWA), has operational and equipment requirements for commercial vehicles used in interstate commerce. We will forward a copy of your letter to the FHWA for information about those requirements. I hope this information is helpful. Sincerely, Paul Jackson Rice Chief Counsel Enclosures"; |
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ID: aiam0502OpenMr. G. E. Fouche', Jr., Project Leader, Kendall Company, P. O. Box 1828, 6300 Carmel Road, Charlotte, NC, 28201; Mr. G. E. Fouche' Jr. Project Leader Kendall Company P. O. Box 1828 6300 Carmel Road Charlotte NC 28201; Dear Mr. Fouche': This is in reply to your letter of November 2, 1971, concerning th application of Motor Vehicle Safety Standard No. 302, 'Flammability of Interior Materials,' to synthetic fabrics. You state that certain of these fabrics do not ignite when tested with a stationary flame as they melt and shrink away from the flame, but burn faster than the 4-inch-per-minute rate if the flame is moved to keep it in contact with the fabric. You ask whether materials that behave in this manner comply with the standard.; The standard requires that the vehicle components specified in S4.1 o the standard meet the burn rate requirements when tested as provided in S5.3 of the standard. This procedure specifies a stationary flame. Consequently, we would consider materials which melt and shrink away from the flame, but do not ignite, as long as the other aspects of the test procedure were followed, to comply with the standard.; Sincerely, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam5350OpenMr. Michael E. Klima Managing Engineer Failure Analysis Associates, Inc. 2100 East Maple Road, Suite 200 Birmingham, MI 48009; Mr. Michael E. Klima Managing Engineer Failure Analysis Associates Inc. 2100 East Maple Road Suite 200 Birmingham MI 48009; Dear Mr. Klima: This responds to your letter of March 29, 1994, to Mr Edward Jettner of this agency concerning the dynamic testing requirements of Standard No. 208, Occupant Crash Protection. Your questions concern the application of this standard to a pickup truck manufactured in April 1988 with a gross vehicle weight rating (GVWR) of 4,400 pounds. You asked whether the injury criteria in S6 apply to this truck, whether a 35 mph fixed barrier crash test is required, and which sections of Standard No. 208 apply to this truck. The safety belt installation requirements for all vehicle types are set forth in Standard No. 208. Section S4.2.1 of Standard No. 208 gives vehicle manufacturers a choice of three options for providing occupant crash protection in trucks and multipurpose passenger vehicles with a GVWR of 10,000 pounds or less, manufactured on or after January 1, 1976 and before September 1, 1991. Option 1, set forth in S4.1.2.1, requires vehicle manufacturers to provide automatic protection at the front outboard seating positions, and either meet the lateral crash protection and rollover requirements by means of automatic protection systems or have manual safety belts at the front outboard seating positions such that those positions comply with the occupant protection requirements when occupants are protected by both the safety belts and the automatic protection. Option 2, set forth in S4.1.2.2, requires vehicle manufacturers to provide a lap or lap/shoulder safety belt at every seating position, have automatic protection for the front outboard seats, and have a warning system for the safety belts provided. Option 3, set forth in S4.1.2.3, requires the manufacturer to install lap or lap/shoulder safety belts at every seating position and to have a warning system for those belts. According to your letter, the manufacturer installed Type 2 seat belt assemblies at the front outboard seating positions. This suggests that the manufacturer chose to comply with Option 3. Under this option, the only requirements in Standard No. 208 that those belts were required to comply with were S7.1, S7.2, and S7.3. The belts were also required to comply with the requirements of Standard No. 209, Seat Belt Assemblies. The manufacturer was not required to certify that the vehicle complied with the dynamic testing requirements of Standard No. 208. The injury criteria in S6 of the standard are applicable only to vehicles which must comply with the dynamic testing requirements. Standard No. 208 does not include a 35 mph fixed barrier crash test requirement. The dynamic crash test in Standard No. 208 is barrier crash test at any speed up to 30 mph. NHTSA does perform some 35 mph barrier crash tests as part of the New Car Assessment Program (NCAP). NCAP is a consumer information program, not a safety compliance test. NHTSA does not test every vehicle under this program. In the 1993 model year program, NHTSA tested 37 new vehicles and released results on 68 additional vehicles which had been tested previously and had not changed significantly in model year 1993. 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; |
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ID: aiam2495OpenMr. David Munafo, Commercial Plastics, 98-34 Jamaica Avenue, Richmond Hill, NY 11418; Mr. David Munafo Commercial Plastics 98-34 Jamaica Avenue Richmond Hill NY 11418; Dear Mr. Munafo: This responds to your letter of December 7, 1976, regarding the use o plastic glazing materials for side windows of school buses. You asked what materials are permitted by Federal regulations for school bus side windows and whether Federal laws concerning the materials that may be used preempt State laws on the same subject.; Section 103(d) of the National Traffic and Motor Vehicle Safety Act (1 U.S.C. S1381 *et*. *seq*.) provides in part:; >>>Whenever a Federal motor vehicle safety standard established unde this title is in effect, no State or political subdivision of a State shall have any authority either to establish, or to continue in effect, with respect to any motor vehicle or item of motor vehicle equipment any safety standard applicable to the same aspect of performance of such vehicle or item of equipment which is not identical to the Federal standard.<<<; Safety Standard No. 205, *Glazing Materials* (49 CFR 571.205) currentl does not permit the use of plastic glazing in bus side windows. Therefore, State laws that permit plastic glazing are in direct conflict with Standard No. 205, and it is the agency's opinion that they would be preempted.; I would point out that the agency recently issued a proposal to amen Standard No. 205 that would permit the use of rigid plastic glazing in bus side windows (41 FR 56837, Dec. 30, 1976). I am enclosing a copy of this proposal for your information. I am also enclosing a copy of Standard No. 205 and the ANS Z26 standard that is incorporated by reference in Standard No. 205. From these standards you can determine the various types of glazing materials that are permitted for side windows and the requirements that the glazing must meet.; Regarding your question about replacement glazing, Standard No. 205 i not a vehicle standard and is applicable to all glazing for use in motor vehicles, whether the glazing is to be installed in new vehicles or as replacement in used vehicles. Therefore, glazing manufacturers and fabricators cannot produce glazing to be used in a given location in a vehicle unless the standard permits that type of glazing to be used in that location, regardless of whether it is original or replacement glazing.; Sincerely, Frank Berndt, Acting Chief Counsel |
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ID: aiam0152OpenMr. Yoshiyuki Mizuno, Factory Engineer, Nissan Motor Corporation, 400 County Avenue, Secaucus, NJ 07094; Mr. Yoshiyuki Mizuno Factory Engineer Nissan Motor Corporation 400 County Avenue Secaucus NJ 07094; Dear Mr. Mizuno:#Thank you for your letter of March 7, 1969, to Dr William Haddon, Jr., concerning the location and the identification of the windshield washer switch on the steering column.#The system as you describe it appears to conform to Federal Motor Vehicle Safety Standard No. 101, however, the Bureau does not issue approvals of any specific system, and the development of equipment to comply with the standard is the responsibility of the individual manufacturer.#In reference to your second question about the identification of the windshield washer switch, Paragraph S3.2 reads, in part, '.... The following controls, when mounted on the instrument panel, shall be identified to permit recognition -- >>>... (c) Windshield Washing System, ....'<<<#This section of the regulation does not apply to the identification of controls in any position other than on the instrument panel.#Sincerely, Charles A. Baker, Office of Standards on Accident Avoidance, Motor Vehicle Safety Performance Service; |
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ID: aiam4111OpenMr. Marshall D. Carter, Whisper Electric Car AS, 87 Hadsundve, Als, DK-9560 Hadsund, Denmark; Mr. Marshall D. Carter Whisper Electric Car AS 87 Hadsundve Als DK-9560 Hadsund Denmark; Dear Mr. Carter: This is in reply to your letter of February 18, 1986, asking tw questions with respect to the Federal motor vehicle safety standards.; With respect to electric vehicles, you have asked 'is there a standar regulating the minimum length of time that the hazard light must be able to function at a minimum intensity, on the service battery alone?' There is no such standard. The vehicle must be equipped with a hazard warning signal operating unit designed to conform to SAE J910, January 1966, and a hazard warning signal flasher designed to conform to SAE J945, February 1966, but there is no requirement in the Federal motor vehicle safety standard on vehicle lighting, Standard No. 108, that the hazard warning signal flashers perform for a minimum specified period of time in service.; You have also asked 'Is there a requirement that the vehicle b equipped with an illuminated display, indicating gear selection?' We are unable to confirm your conclusion that there is no such requirement under Standard No. 101. Paragraph S3.2 of Standard No. 102 requires that identification of shift lever positions or patterns be permanently displayed in front of the driver. Paragraph S5.3.1 of Standard No. 101 requires illumination of the 'gauges' listed in Column 1 of Table 2 that are accompanied by the word 'Yes' in Column 5. The last 'gauge' listed is 'Automatic gear position', and the word 'Yes' appears in Column 5. The automatic gear position is a 'gauge' as defined by paragraph S4 of Standard No. 101, 'a display that is listed in ...Table 2 and is not a telltale'. Thus the Federal standards do require illumination of the gear positions of automatic transmissions, but not of manual ones.; I hope that this responds to your questions. Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam1313OpenMr. Gordon M. Bradford, Vice President, Corporate Development, American Safety Equipment Corporation, 16055 Ventura Boulevard, Encino, CA 91316; Mr. Gordon M. Bradford Vice President Corporate Development American Safety Equipment Corporation 16055 Ventura Boulevard Encino CA 91316; Dear Mr. Bradford: This is in reply to your letter of October 5, 1973, concerning you proposed use of a tension reliever device in a seat belt retractor. As we understand the concept of the tension reliever, it allows a small amount of slack to be introduced into the webbing by a mechanism roughly similar to that of a window shade. If the webbing is pulled smoothly back and forth, the retractor exerts a normal retractive force. If, however, the retraction is halted at a certain point, as when the belt comes to rest against an occupant's shoulder, the reliever engages and the occupant is relieved of the active pull of the retractor until he moves forward by an inch or two and disengages the reliever.; Your initial question is whether a reliever-equipped retractor will b considered to meet the retraction force requirements of S4.3(j)(6) of Motor Vehicle Safety Standard No. 209. You state that it will meet the test so long as the procedures of S5.2(j) are strictly observed and no oscillations are introduced by the test apparatus. If the facts are as you state, it is our opinion that the retractor would meet S4.3(j)(6).; Your other question, as clarified by telephone on November 1, 1973, i whether we have reservations about the concept of a tension reliever that would lead us to bar its use through amendment of Standard No. 209. Based on the information presently available, we have no such reservations.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam3284OpenCharles M. Kneip, Vehicle Services Division, Department of Motor Vehicles, Lincoln, NE 68509; Charles M. Kneip Vehicle Services Division Department of Motor Vehicles Lincoln NE 68509; Dear Mr. Kneip: This is in response to your letter of May 7, 1980, in which you aske whether the proposed Nebraska certificate of title may be used as a substitute for the Federal odometer disclosure form required by 49 CFR Part 580.; The Nebraska title differs from the minimum Federal requirements i that there is no certification that the odometer reading reflects the actual mileage or the mileage over 99,999 miles, or is not the actual mileage. The buyer is not required to sign the Nebraska title as he is the Federal form (sic). In addition, your title does not refer to the legal consequences of a false disclosure. If you can make these additions, the Nebraska title will satisfy the Federal requirements.; For your information, I have enclosed a copy of the *Federal Register notice which discusses the short form odometer disclosure that States may use on their titles to satisfy Federal requirements, a letter to Maryland in which we indicate that formal approval by NHTSA is not necessary if the title contains the specified information, and sample titles that the NHTSA has approved.; If you need any further inforamtion, please do not hesitate to contac us.; Sincerely, John Womack, Assistant Chief Counsel |
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ID: aiam4541OpenMr. Gerald Peterson Taraco Enterprises Inc. Empire Plaza 23 Empire Drive St. Paul, MN 55103; Mr. Gerald Peterson Taraco Enterprises Inc. Empire Plaza 23 Empire Drive St. Paul MN 55103; "Dear Mr. Peterson: This responds to your May 17, 1988 letter to m asking for 'information on petitions filed, concerning the safety problems on trucks.' You also enclosed for the agency's information materials on the product you manufacture called a 'Truk-Hedrest.' According to the brochures you sent, the Truk-Hedrest attaches to the rear window of a vehicle by means of velcro and 'is designed to help protect the head of the driver and passenger of a truck or van in an accident when their head is snapped back against the rear window or bulkhead of a vehicle.' You also enclosed a copy of an August 28, 1987 letter which Mr. Carl Clark of this agency sent you regarding your product. The latter part of this letter addresses statements in your brochures relating to our regulations and the Truk-Hedrest. The National Highway Traffic Safety Administration (NHTSA) shares your concern for light truck safety and is currently reviewing a number of actions intended to improve the protection for occupants of such vehicles. This review has been described in detail in the enclosed reports to Congress issued by NHTSA in May 1987 ('Light Truck and Van Safety') and April 1988 ('Safety Programs for Light Trucks and Multipurpose Passenger Vehicles'). Among the rulemaking activities considered by NHTSA for light trucks is a possible extension of Safety Standard No. 202, Head Restraints, to those vehicles. The agency is presently reviewing petitions for rulemaking on this subject from Mr. Dale T. Fanzo of Bethel Park, Pennsylvania and Mr. Mark E. Goodson of Lewisville, Texas. I have enclosed copies of these petitions for your information. With regard to the brochures and materials you sent on your product, I would like to first to make it clear that Mr. Clark's letter on the Truk-Hedrest only expressed his personal opinions and interests concerning your product. His letter does not represent any official agency position regarding light truck safety in general or regarding your product in particular. Mr. Clark's letter was neither an approval nor endorsement of your product by this agency. NHTSA does not approve motor vehicles or motor vehicle equipment, nor do we endorse any commercial products. In addition, the agency cannot as a matter of law and will not as a matter of policy determine the extent, if any, of the occupant protection provided by any commercial product apart from the context of an actual enforcement proceeding. Thus, the agency does not concur in any manner with Mr. Clark's assessement that the Truk-Hedrest 'does indeed provide excellent head protection' or with any other statement as to the effectiveness of your product. Second, your brochures imply that the Truk-Hedrest has been shown to help protect against possible neck and head injuries when tested to 'NHTSA guidelines.' NHTSA has neither adopted or even developed guidelines for testing the Truk-Hedrest. Again, in his letter to you Mr. Clark provided only his personal opinion on certain aspects of your product testing program. He expressed no agency recommendations or 'guidelines' for testing a product such as yours 'for rear end collisions up to 50 MPH,' or with bowling balls, since no such guidelines exist. My final clarification concerns the statements in your brochures that the Truk-Hedrest 'Passes MVSS-302 Test for fire and toxic fumes.' Please note that Standard No. 302, Flammability of Interior Materials, addresses only the flammability resistance of vehicle components and not the toxicity of gases from burning materials. With respect to your statement about meeting the FMVSS 302 requirements regarding fire, please note that if the Truk-Hedrest did not in fact meet those requirements and were installed in a vehicle by a motor vehicle manufacturer, distributor, dealer or repair business, there could be a violation of the National Traffic and Motor Vehicle Safety Act. Section 108(a)(2)(A) of the Act prohibits those persons from rendering inoperative any device or element of design installed pursuant to the Federal motor vehicle safety standards. Installation of rapidly burning materials could vitiate the compliance of the materials which were present in the vehicle at the time of its sale to the first consumer and were certified as meeting FMVSS 302. To repeat, in his letter to you Mr. Clark was only expressing his personal opinions and interests concerning your product and made no statements that should be construed as official agency positions. NHTSA does not endorse the Truk-Hedrest nor do we make any determination on the extent, if any, of the occupant protection provided by your product. I regret any confusion that may have resulted from Mr. Clark's letter to you on the Truk-Hedrest. Please contact my office if you have further questions. Sincerely, Erika Z. Jones Chief Counsel Enclosures"; |
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ID: aiam1743OpenMr. John Massey, Fontaine Truck Equipment Co., 9051 Sorenson Avenue, Santa Fe Springs, CA 90670; Mr. John Massey Fontaine Truck Equipment Co. 9051 Sorenson Avenue Santa Fe Springs CA 90670; Dear Mr. Massey: Mr. S. G. Holder of the Fontaine Truck Equipment Company asked th National Highway Traffic Safety Administration to explain for your benefit the requirements of Standard No. 121, *Air brake systems*, for alteration of wheelbase and installation of a liftable axle on incomplete or complete vehicles by a dealer like yourself.; I have enclosed a copy of the standard as requested. It lists severa requirements which would be affected by the addition of an additional axle. These changes can be complex, and we believe that some assistance from the manufacturer of the axle may be necessary to assist a final-stage manufacturer or vehicle alterer like yourself in meeting the certification requirements. I enclose a letter to a liftable axle manufacturer which explains the responsibilities of the various parties to each other.; Standard No. 121 was issued in February 1971 in part to reduce th incompatibility in brake performance between the larger air-braked vehicles on the highway and other highway users. Its provisions substantially improve the stopping distance performance and other braking characteristics of air-braked vehicles. To meet these requirements, chassis-cab and other vehicle manufacturers have limited the modifications which may be made to their brake system design so that a vehicle will remain in compliance.; It is for this reason that final-stage manufacturers and vehicl alterers are more limited than previously in the modifications which they can undertake. Wheelbase alteration is an example of the type of modification which seriously affects brake system performance. We expect experience with Standard No. 121 will justify greater freedom in the future for such modifications as wheel base alteration.; Yours truly, Richard B. Dyson, Acting 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.