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: nht76-5.49OpenDATE: 04/07/76 FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA TO: HON. M. L. Esch - H.O.R. TITLE: FMVSS INTERPRETATION TEXT: The Secretary of Transportation has asked me to respond to your March 16, 1976, request for all information submitted to him since December 31, 1975, concerning the safety and economic feasibility of air cushion restraint systems or, in the alternative, the specific basis for withholding particular documents. We interpret your request to include documents submitted to the Office of the Secretary or to the public docket on passive restraints. All materials concerning the safety and economic feasibility of air cushion systems that have been placed in the public docket are enclosed. These documents include all material on air cushion systems provided to the Assistant Secretary for Systems Development and Technology and to the Assistant Secretary for Environment, Safety and Consumer Affairs during their recent visits to General Motors Corporation, Ford Motor Company, and Chrysler Corporation. Films submitted to the docket that support this material are available for viewing at your request. The NHTSA has provided material to the Office of the Secretary that discusses the value of requiring passive restraints in motor vehicles. All of this material consists of intra-agency memoranda that contain the opinions of agency staff on the considerations underlying a decision concerning passive restraints. The preparation of this material involved choosing and weighing data and making certain assumptions. I conclude that it is important to have full and free staff input to this decision-making process. Accordingly, I deny your request for this information pursuant to the exemption in the Freedom of Information Act for intra-agency memoranda (5. U.S.C. @ 552(b)(5)). I am the person responsible for this decision. Pursuant to the Regulations of the U.S. Department of Transportation (49 CFR 7), this decision, to the extent information you seek is not released, may be appealed to John Hart Ely, Esq., General Counsel of the Department, whose decision will be administratively final. Your application for reconsideration must be made in writing within sixty days from the date of receipt of the original denial and must include all information and arguments relied upon in your original request. Such application must indicate that it is an appeal from a denial of a request made under the Freedom of Information Act and the envelope in which the application is sent must be prominently marked with the letters "FOIA". Sincerely, Enclosures |
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ID: 77-4.17OpenTYPE: INTERPRETATION-NHTSA DATE: 10/17/77 FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA TO: Midland-Ross Corporation TITLE: FMVSS INTERPRETATION TEXT: This responds to Midland-Ross' July 8, 1977, request for confirmation that the requirement that "[each] service reservoir system shall be protected against loss of air pressure. . .by check valves or equivalent devices" in S5.1.2.3 and S5.2.1.5 of Standard No. 121, Air Brake Systems, permits small losses of air pressure through the check valve of up to 2 psi per minute without constituting noncompliance. The requirement for protection against "loss of air pressure" does permit a small amount of leakage, in recognition of the fact that no fitting can be perfectly air tight. While the standard does not presently specify a rate of permissible air loss in S5.1.2.3 or S5.2.1.5, the agency has adopted a maximum loss of 10 psi in 10 minutes as meeting the requirement for protection against loss of air pressure. The agency is considering adding such a specification to the standard in the future by interpretive amendment. SINCERELY, MIDLANDROSS CORPORATION July 8, 1977 Thomas W. Herlihy Office of Chief Council National Highway Traffic Safety Adm. Subject: FMVSS #571.121, Section S5.1.2.3. Midland-Ross Corporation is a manufacturer of air brake actuation equipment for heavy duty trucks. We therefore manufacture components which are used by truck manufacturers for compliance with FMVSS #571.121. We are asking for interpretation of the requirement for check valves, specifically as it relates to section S.5.1.2.3. Section S.5.1.2.3 states: "Each service reservoir system shall be protected against loss of air pressure due to failure or leakage in the system between the service reservoir and the source of air pressure, by check valves or equivalent devices whose proper functioning can be checked without disconnecting any air line or fitting". The statement "loss of air pressure" has not been qualified and can be interpretated to mean zero leakage. It is common knowledge that check valves being produced today have a leakage tolerance. For example, Midland-Ross 100% inspects check valves and allows a maximum leakage of 330 ccm (cubic centimeters/minute) leakage at 20 psi. It is also common knowledge that some leakage will exist in connections upstream to the check valve through air lines, fittings and valves. In fact the accepted industry standards have been to allow a maximum leakage of 2 psi pressure drop in one minute (reference: SAE J-890, California Highway Patrol; DOT part 570, Inspection Standard for Motor Vehicles). |
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ID: 21937.drnOpen Jiri Misik, Chief 293 60 Mlad Boleslav Dear Mr. Misik: This responds to your request for information about "US field of vision" requirements for motor vehicle windshields for passenger cars and light duty vehicles. As explained below, the United States has no forward field of view standard for these vehicles. In your letter, you noted that Federal Motor Vehicle Safety Standard No. 104, Windshield wiping and washing systems, describes Areas "A," "B" and "C" to be cleared in motor vehicle windshields. In contrast you noted that in Europe: In our case the edge of area "A" and "B" ... is not placed on the windshield but on the steel structure or even on the side window. This case is not mentioned in any US legislation which is related directly to wipe, wash and forward vision, anyway. Forward field of vision is only clearly defined in European Directive 77/649 and Australian ADR 8, clause 8.3. With this background, you ask whether "there is a mandatory US provision to place the edge of 'A' area on the windscreen with regard to forward field of vision." In response to your question, no provision in the U.S. Federal Motor Vehicle Safety Standards specifies forward field of view requirements for vehicles other than school buses. As you note, we have Standard No. 104, which establishes requirements for motor vehicle windshield wiping and washing systems. Since Standard No. 104 regulates windshield wiper performance, it defines each of Areas "A," "B" and "C" so that only the part of each Area that is within the glazing 25 millimeters inboard of the daylight opening is counted for the computation of the minimum cleared percentage. Please note that these are requirements for areas of the motor vehicle windshield to be cleared of water or other liquids. We have no standard analogous to EU Directive 77/649 which would use Areas "A," "B" and "C" to specify areas of mandatory forward fields of view. Another indication that Standard No. 104 does not specify forward fields of vision is seen in the fact that there is no requirement that Area "A," as bounded by the angles specified in Tables I, II, III or IV, must be completely included on the windshield glazing. I hope this information is helpful. If you have any further questions, please contact Dorothy Nakama of my staff at this address or at (202) 366-2992. Our FAX number is (202) 366-3820. Sincerely, Frank Seales, Jr. ref:104 |
2000 |
ID: nht70-1.48OpenDATE: 03/25/70 FROM: AUTHOR UNAVAILABLE; R. A. Diaz; NHTSA TO: The Society of Motor Manufacturers and Traders Limited TITLE: FMVSS INTERPRETATION TEXT: Thank you for your letter of February 2, 1970, to the Federal Highway Administration, transmitting the August 1969, edition of the S.M.M.T. Tyre and Wheel Engineering Manual. Your letter also expressed your intention of having the 1969 manual supercede the 1965/66 data book as referenced in Section 83 of Standard No. 109. As we stated in our letter of March 14, 1969, to Mr. Woodbridge, Chief Engineer of S.M.M.T., "Federal Motor Vehicle Safety Standard No. 109, within Section 83, lists the Tyre and Wheel Engineering Data Book dated 1965/66 of the Society of Motor Manufacturers and Traders Limited (S.M.M.T.), "as one of the references containing acceptable test rims. When Standards No. 109 and 110 were developed, the National Highway Safety Bureau accepted the S.M.M.T. 1965/66 Data Book tire and rim combinations based on established usage. We did not, nor do we at present intend to accept general updating of these referenced publications, either foreign or domestic, as valid reasons for amending Standards No. 109 and 110. Consequently, any new tire size designations or alternative rim sizes that you wish to list within Standards No. 109 and 110 will have to comply, on an individual basis, with the abbreviated guidelines as outlined in the October 5, 1968, Federal Register. |
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ID: nht92-8.9OpenDATE: March 31, 1992 FROM: Tom Mario -- Vice President Sales, Sealco Air Controls, Inc. TO: Steve Wood -- Office Staff Counsel, NHTSA TITLE: None ATTACHMT: Attached to letter dated 5/21/92 from Paul J. Rice to Tom Mario (A39; Std. 121) TEXT: I had recent phone conversation with Mr. Richard Carter about trailer manufacturers using the standard 121 air brake system, "protected separate reservoir", after October 8, 1992. Mr. Carter said his interpretation is that you could use, "protected separate reservoir" or 49 CFR part 571 (Docket No. 90-3; Notice 2). Also requesting your interpretation, for full trailer, rear axles with new system (Docket No. 90-3; Notice 2) which air brake system is required for front axle (turntable) with service brake chambers? Also multiple axle trailers, with new system (Docket No. 90-3; Notice 2) on some axles and other axles with service chambers, which air brake system is required? |
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ID: nht94-5.3OpenTYPE: INTERPRETATION-NHTSA DATE: December 8, 1994 FROM: Philip R. Recht -- Chief Counsel, NHTSA TO: Samson Helfgott, Esq., Helfgott & Karas, P.C. TITLE: Re: Your Ref. No.: 12.065 ATTACHMT: ATTACHED TO LETTER DATED 09/29/94 FROM SAMSON HELFGOTT TO JOHN WOMAK (OCC 10394) TEXT: We have received your letter to John Womack, the former Acting Chief Counsel of this agency, responding to his letter to you of July 20, 1994. Thank you for enclosing a copy of his letter for ready reference. Our previous letter to you was without the benefit of the diagram of the Caine system which you have now enclosed. The system is intended to be placed "along the side of trucks and other vehicles." It consists of three read lamps mounted over three ambe r (yellow) ones, the array installed between the amber front side marker lamp and the red rear side marker lamp. In normal operation the amber lamps are used as "running lights" but will be turned off when the red lamps are illuminated in a steady burni ng state upon application of the brake pedal. The three amber lamps will flash to indicate that the vehicle is turning. All six lamps will flash when the hazard indicator switch is on. If the turn signal is on and the driver's foot is on the brake ped al, the amber lamps will flash while the red ones illuminate in a steady burning state. At 32 candela, the turn signal lamps will be at a higher intensity than the running lamps which operate at 3 to 5 candela. These are within NHTSA specifications. Y ou ask whether this system will be in violation of Standard No. 108. This office has corresponded with you on lighting matters on a number of occasions and you are well aware that supplementary lighting equipment is prohibited as original equipment only if it impairs the effectiveness of lighting equipment that is require d by Standard No. 108. This determination is to be made by the manufacturer or dealer who installs the equipment and NHTSA will not question it unless it is clearly erroneous. |
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ID: nht88-3.41OpenTYPE: INTERPRETATION-NHTSA DATE: 09/12/88 EST FROM: ERIKA Z. JONES -- CHIEF COUNSEL; NHTSA TO: DAVIS THEKKANATH -- SR. SUPERVISING ENGINEER, OSHKOSH TRUCK CORPORATION ATTACHMT: MEMO DATED 11-18-87, SUBJECT: FMVSS 121, TO NHTSA, FROM DAVIS THEKKANATH -- OSHKOSH TRUCK CORPORATION TEXT: This responds to your letter requesting an interpretation of Safety Standard No. 121, Air Brake Systems. Section S5.1.1 of the standard requires trucks and buses to have an air compressor of sufficient capacity to bring the pressure in the supply and se rvice reservoirs from 85 psi to 100 psi within a specified time. You inquired about the meaning of this requirement in the context of a truck with a trailer behind it. You particularly asked whether the air compressor capacity requirement includes the volume of service reservoirs for the trailer. As discussed below, only the truck reservoirs need to be considered for this requirement. By way of background information, the National Highway Traffic Safety Administration does not provide approvals for motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manuf acturer to ensure that its vehicles and equipment meet applicable standards. The following represents our opinion based on the facts provided in your letter. Section S5.1 and S5.1.1 of Standard No. 121 read as follows: S5.1 Required equipment -- trucks and buses. Each truck and bus shall have the following equipment: S5.1.1 Air Compressor. An air compressor of sufficient capacity to increase air pressure in the supply and service reservoirs from 85 pounds per square inch (p.s.i.) to 100 p.s.i. when the engine is operating at the vehicle manufacturer's maximum rec ommended r.p.m. within a time, in seconds, determined by the quotient (Actual reservoir capacity x 25)/Required reservoir capacity. The reference in section S5.1.1 to "supply and service reservoirs" refers only to the supply and service reservoirs in the truck or bus subject to the requirement. Similarly, the term "actual reservoir capacity" refers only to the actual reservoir capac ity of that truck or bus, and the term "required reservoir capacity" refers only to the reservoir capacity required for that truck or bus. Thus, for a truck designed to tow an air-braked trailer, only the truck's reservoirs need to be considered for this requirement. For purposes of testing, the towing vehicle protection system would be activated. While Standard No. 121 does not specify air compressor capacity for towing vehicles in terms which address towed vehicles, we assume that manufacturers of vehicles designed to tow air-braked vehicles will design them to have sufficient air compressor cap acity to ensure safe braking performance under conditions of reasonably foreseeable use, including when they are towing air-braked vehicles. |
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ID: 2947oOpen Mr. Davis Thekkanath Dear Mr. Thekkanath: This responds to your letter requesting an interpretation of Safety Standard No. l2l, Air Brake Systems. Section S5.l.l of the standard requires trucks and buses to have an air compressor of sufficient capacity to bring the pressure in the supply and service reservoirs from 85 psi to l00 psi within a specified time. You inquired about the meaning of this requirement in the context of a truck with a trailer behind it. You particularly asked whether the air compressor capacity requirement includes the volume of service reservoirs for the trailer. As discussed below, only the truck reservoirs need to be considered for this requirement. By way of background information, the National Highway Traffic Safety Administration does not provide approvals for motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles and equipment meet applicable standards. The following represents our opinion based on the facts provided in your letter. Sections S5.l and S5.l.l of Standard No. l2l read as follows: S5.l Required equipment--trucks and buses. Each truck and bus shall have the following equipment: S5.l.l Air Compressor. An air compressor of sufficient capacity to increase air pressure in the supply and service reservoirs from 85 pounds per square inch (p.s.i.) to l00 p.s.i. when the engine is operating at the vehicle manufacturer's maximum recommended r.p.m. within a time, in seconds, determined by the quotient (Actual reservoir capacity x 25)/Required reservoir capacity. The reference in section S5.l.l to "supply and service reservoirs" refers only to the supply and service reservoirs in the truck or bus subject to the requirement. Similarly, the term "actual reservoir capacity" refers only to the actual reservoir capacity of that truck or bus, and the term "required reservoir capacity" refers only to the reservoir capacity required for that truck or bus. Thus, for a truck designed to tow an air-braked trailer, only the truck's reservoirs need to be considered for this requirement. For purposes of testing, the towing vehicle protection system would be activated. While Standard No. l2l does not specify air compressor capacity for towing vehicles in terms which address towed vehicles, we assume that manufacturers of vehicles designed to tow air-braked vehicles will design them to have sufficient air compressor capacity to ensure safe braking performance under conditions of reasonably forseeable use, including when they are towing air-braked vehicles. Sincerely,
Erika Z. Jones Chief Counsel ref: 121 d:9/l2/88 |
1970 |
ID: nht95-1.32OpenTYPE: INTERPRETATION-NHTSA DATE: January 19, 1995 FROM: Jiro Doi -- Vice President, MITSUBISHI MOTORS AMERICA, INC. TO: Philip Recht -- Chief Counsel, NHTSA TITLE: NONE ATTACHMT: ATTACHED TO 5/5/95 LETTER FROM JOHN WOMACK TO JIRO DOI (A43; PART 541) TEXT: Dear Mr. Recht: On behalf of Mitsubishi Motors America, Inc., a U.S. subsidiary of Mitsubishi Motors Corporation, I request a legal interpretation concerning Part 541 Federal Motor Vehicle Theft Prevention Standard, particularly our question regards Part 541.5(a)(2) whi ch requires that the transmission be marked with either the VIN or a VIN derivative. The clutch housing, for vehicles with manual transmissions (or converter housings for vehicles with automatic transmissions), is attached to the transmission (See Attachment) via bolts that may be removed allowing the clutch housing (or converter housing ) to separate from the transmission. Nevertheless, we believe the clutch housing may be considered a part of the transmission. Therefore, we believe marking the clutch housing (or converter housing) complies with Part 541.5(a)(2). Please provide us with your interpretation regarding this issue. If you have any questions, please contact me at (202) 223-5730. Drawing omitted. |
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ID: GF007036OpenMr. Robert M. Clarke Dear Mr. Clarke: This is in response to your letter of September 15, 2003, seeking clarification of the two effective dates for the new heavy vehicle antilock brake system (ABS) performance requirements in Federal Motor Vehicle Safety Standards (FMVSS) No. 121, and FMVSS No. 105. [1] In your letter, you indicated your understanding that "complete vehicle" manufacturers were subject to the effective date of July 1, 2005.You also indicated your understanding that "incomplete vehicle" manufacturers, including "final stage" manufacturers and "intermediate stage" manufacturers were subject to the effective date of July 1, 2006. You ask whether a "chassis-cab" manufacturer [2] would also qualify as an "incomplete vehicle" manufacturer, and thus be subject to the July 1, 2006, effective date. As discussed below, our answer is yes.
The new regulatory text for FMVSS No. 105 contains similar language with respect to the effective dates. The preamble to the final rule explains that "vehicles built in two or more stages must meet the braking-in-a-curve tests requirements on or after July 1, 2006." The preamble also indicates that the additional lead time was necessary in order to enable early stage manufacturers to provide complying incomplete vehicles to final stage manufactures. [3] With respect to the effective date for vehicles manufactured in two or more stages, the final rule does not differentiate between the different stages of the manufacturing process or different categories of incomplete vehicles. Instead, we provided an effective date of July 1, 2006, for all vehicles built in two or more stages. Accordingly, all vehicles built in two or more stages, including chassis-cabs, are subject to the effective date of July 1, 2006. With respect to your last question, the abbreviation "LLVW" appearing in Table 1 of the August 11 Final Rule, stands for "lightly loaded vehicle weight." The term carries the same meaning in FMVSS No. 121 as it does in FMVSS No. 105 where it is defined as unloaded vehicle weight plus up to 1,500 lb. We intend to add this same definition to FMVSS No. 121 at a future date. I hope this information is helpful. If you have any further questions, please feel free to contact George Feygin of my staff at this address or by telephone at (202) 366-2992. Sincerely, Jacqueline Glassman ref:121 [1] The new requirements were published in the Final Rule on August 11, 2003 (68 FR 47485). [2] A "chassis-cab" is one type of incomplete vehicle. [3] See Id. at 47493. |
2003 |
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.