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: aiam3564OpenMr. Edward H. Clapp, President, Transquip Industries, Inc., 1222 RepublicBank Oak Cliff, Dallas, TX 75208; Mr. Edward H. Clapp President Transquip Industries Inc. 1222 RepublicBank Oak Cliff Dallas TX 75208; Dear Mr. Clapp: This responds to your recent letter asking whether Federal regulation allow a brake hose to be used as a dual purpose hose for both the service brakes and the emergency brake.; Standard No. 121, *Air Brake Systems*, does not preclude the use o common components in parking, emergency, and service air brake systems. Accordingly, nothing would prevent you from using a common hose in those systems. However, the common component would have to comply with the requirements for each system. This means that a failure of the hose would always be treated as a failure in the parking, emergency and service brake systems. Applying this to the standard in section S5.2.1.1, it would be necessary for the parking brakes to be capable of being released with a failure of the common hose at any time. If your system cannot perform in this manner, which it appears it cannot, it could not comply with the safety standard.; Our engineering staff has reviewed your brake system very carefull over the past years. It appears that your system can be properly plumbed in a manner that it would seem to comply with the requirements. You have continued to seek slightly less expensive methods to plumb your system. In our opinion, these methods would not be capable of complying with the standard. We cannot see how your system can comply with the standard without traditional plumbing that is being used by many brake manufacturers today. Accordingly, we suggest that you concentrate your efforts on constructing your system in that manner.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam1559OpenBayerische Motoren Werke AG,8 Munchen 40,Postf. 40 02 40,Germany; Bayerische Motoren Werke AG 8 Munchen 40 Postf. 40 02 40 Germany; Gentlemen:#This respond's to BMW's June 20, 1974, question whethe 7/16-inch vacuum tubing may be manufactured and sold although it does not appear in Table V of Standard No. 106-74, and if so, what Table V values would be used in testing it.#Table V established test values for vacuum hose but does not limit the vacuum hose sizes which may be manufactured and sold in conformity with the standard. You are free to utilize 7/16- inch vacuum hose, and the Table V test values for 15/32-inch hose should be used to test 7/16-inch hose.#We are considering the addition of an entry in Table V to cover 7/16-inch hose in the near future.#Yours truly,Richard B. Dyson,Acting Chief Counsel; |
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ID: aiam3071OpenMr. Hisakazu Murakami, Nissan Motor Co., Ltd., Suite No. 1012, 1028 Connecticut Avenue, N.W., Washington, DC 20036; Mr. Hisakazu Murakami Nissan Motor Co. Ltd. Suite No. 1012 1028 Connecticut Avenue N.W. Washington DC 20036; Dear Mr. Murakami: This responds to your letter of July 3, 1979, asking several question concerning the definition of 'designated seating position' (49 CFR 571.3), as that term was recently amended (44 FR 23229, April 19, 1979).; In your first question, you ask for confirmation that any bench o split-bench seat with less than 50 inches of hip room may never be required to have three or more than three designated seating positions, notwithstanding the capability of accommodating a person at least as large as a fifth percentile adult female. Your assumption is incorrect. As noted in the preamble to the recent amendment, the 50-inch specification does not mean that some vehicle seats with less than 50 inches of hip room should not also have more than two designated seating positions, if the vehicle and seat design is such that three positions would likely be used (44 FR 23232). The specification is merely the amount of space the agency will consider as conclusive evidence that there should be at least three designated seating positions. The 50-inch caveat was included in the definition to simplify determinations of proper seating capacity by both manufacturers and the agency.; Your second question involves technical aspects of the amende definition of 'designated seating position'. The definition specifies that 'hip room' is to be measured in accordance with SAE J1100(a). That standard defines 'hip room' as,; >>>'the minimum dimension measured laterally between the trimme surfaces on the 'x' plane through the SgRP-front within 1.0 in. (25mm) below and 3.0 in. (76mm) above the SgRP-front and 3.0 in. (76mm) fore and aft of the SgRP-front.' (Area A in your diagrams.)<<<; Your question includes diagrams and asks whether various portions o vehicle seats or other components would be considered 'trimmed surfaces' within SAE Standard J1100(a).; Specifically, you ask whether slightly soft surfaces such as arm rests seat back contours or other raised portions of the seat cushion would be considered 'trimmed surfaces', for purposes of determining the minimum hip room dimension. The answer to your question is yes. The agency would probably consider all of the surfaces illustrated in your letter 'trimmed surfaces' and, strictly speaking, within the meaning of the SAE procedure. This interpretation must be qualified, however. The procedure specifies that 'hip room' is the minimum dimension 'between trimmed surfaces'. If a particular bench seat has distinct sections, the total dimension must be determined by adding the minimum dimensions of each section. For example, your Figure 5 illustrates a bench seat that includes a slightly raised center surface on the tunnel (in the center of the seat over the driveshaft). The lowest portion of Area A as defined in SAE J1100(a) would strike the side of this elevated center section, even though the top portion of Area A would be above the elevation. In such a case, there would be three distinct portions of the seat (the driver's seat, the passenger seat, and the center seat position) that should be measured separately and then added together to get the total dimension. Otherwise, only the portion of the seat on the driver's side of the center elevation would be measured under the strict wording of the SAE procedure--an absurd result.; Regarding these questions about the measurement procedure, I must mak several candid remarks. The agency will not allow manufacturers to avoid the obvious intent of the definition of 'designated seating position' by finding loopholes in the measurement procedure. Further, as noted above, even if the hip room as measured in accordance with SAE J1100(a) is less than 50 inches, a manufacturer may still be required to designate three seating positions. If the measured dimension is less than 50 inches only because of slight elevations or contours on the outside seat cushion, a manufacturer must designate at least three positions if these elevations or contours are not real impediments to three persons occupying the seat.; Determinations of designated seating capacity under the amende definition should not cause manufacturers any real problems. If a manufacturer truly only intends to market a particular bench or split-bench seat for two occupants, he can and should make this obvious by the seat design, regardless of whether the total seat dimension is more than 50 inches or less than 50 inches. One simple way to do this is to install a permanent arm rest or console in the center portion of the seat.; I hope this response has clarified our position and will alleviate an problems you might have in making future determinations of proper designated seating capacity.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3421OpenMr. Keigo Ohgiya, Executive Director, Japan Automobile Tire Manufacturers Association, Inc., 9th Floor, Toranom Building, No. 1-12, 1-Chome Toranomon, Minato-Ku, Tokyo, Japan; Mr. Keigo Ohgiya Executive Director Japan Automobile Tire Manufacturers Association Inc. 9th Floor Toranom Building No. 1-12 1-Chome Toranomon Minato-Ku Tokyo Japan; Dear Mr. Ohgiya: This responds to your recent request for an interpretation of th labeling requirements of Safety Standard No. 109 (49 CFR S571.109). Specifically, your association wants to know if Standard 109 permits tire manufacturers to include the letters 'H,' 'S,' or 'V,' as appropriate, in the tire size designation required to appear on the sidewall of passenger car tires by S4.3(a) of the Standard.; Such labeling is permitted by Standard 109. The speed rating symbol ('h,' 'S,' or 'V') established by the European Tyre and Rim Technical Organization, indicate that a tire is an acceptable high-speed tire. This permits, for example, a knowledgeable purchaser of tires for emergency vehicles to know that these tires are suitable for the higher operational speeds necessary for those vehicles. Use of these symbols in the size designation would not likely confuse the less sophisticated consumer, or otherwise defeat the purpose of the labeling information. Accordingly, use of these symbols is permitted under Standard 109.; If you have any further questions, or need further information on thi matter, please feel free to contact Steve Kratzke of my staff (202-426-2992).; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam3972OpenMr. Donald H. Giberson, Assistant Director, Division of Motor Vehicles, Department of Law and Public Safety, 25 South Montgomery Street, Trenton, NJ 08666; Mr. Donald H. Giberson Assistant Director Division of Motor Vehicles Department of Law and Public Safety 25 South Montgomery Street Trenton NJ 08666; Dear Mr. Giberson: Thank you for your letter of May 17, 1985, to Stephen Oesch of my staf concerning the decorative etching of glazing in vehicles and how it may be affected by our regulations. You explained that the etching is apparently being done by using either vibrator tools with carbide tips, ultra high speed grinders, or sandblasters. You expressed concern that the integrity of the glass may be affected and in some cases the etching is in a position that obstructs the vision of the driver.; You further explained that glazing with etching that obstructs th driver's vision is rejected by your inspectors during New Jersey's annual motor vehicle inspection, but that glazing in areas not used for driving vision cannot be rejected for the same reason. You asked for our comments on this issue.; I hope that the following discussion of how our regulations coul affect the practice of etching glass is of assistance. As you know, our agency has issued Federal Motor Vehicle Safety Standard No. 205, *Glazing Materials*, which sets performance requirements for glazing materials used in new vehicles or sold as items of replacement equipment, a copy of Standard No. 205 is enclosed. If the windows are etched before the vehicle or the piece of replacement glazing is sold, then the person doing the etching would have to certify that the glazing continues to be in compliance with all of the requirements of Standard No. 205, including the light transmittance requirement for glazing in areas requisite for driving visibility. We would be particularly concerned whether the etched items of glazing would continue to comply with the impact resistance requirements of the standard. Please note that impact tests have to be met by items of AS1, AS2, AS3, AS4, AS5, AS8, AS9, AS10, AS11A, AS11B and AS14 glazing regardless of whether the glazing is used in an area requisite for driving visibility. Purchasers of a new vehicle or glazing may themselves alter the vehicle or glazing as they please, so long as they adhere to all State requirements.; If the etching is done in used vehicles, then Section 108(a)(2)(A) o the National Traffic and Motor Vehicle Safety Act may apply, a copy of that section of the Act is enclosed. That section provides that no manufacturer, distributor, dealer, or motor vehicle repair business shall knowingly render inoperative any device or element of design installed on or in a motor vehicle in compliance with an applicable motor vehicle safety standard. Thus, none of those persons may etch a vehicle's glazing if by so doing they would knowingly render inoperative the compliance of the vehicle's glazing with Standard No. 205. Violation of this section can result in Federal civil penalties up to $1,000 for each violation.; If you have any further questions, please let me know. Sincerely, Jeffrey R. Miller, Chief Counsel |
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ID: aiam2660OpenMr. E. M. Ryan, The Coachette Company, P.O. Box 1427, Highway 65 South, Conway, AR 72032; Mr. E. M. Ryan The Coachette Company P.O. Box 1427 Highway 65 South Conway AR 72032; Dear Mr. Ryan: This responds to your August 18, 1977, letter asking whether the hea protection zone requirements of Standard No. 222, *School Bus Passenger Seating and Crash Protection*, apply to a portion of your bus located directly above the side windows.; You enclosed a sketch which details the bus sidewall and roo structure. On that sketch, you have shaded a small area asking whether that portion of the bus constitutes part of the bus sidewall or part of the roof structure. The head protection zone requirements of the standard (S5.3.1.1) do not apply to the sidewalls of school buses.; The National Highway Traffic Safety Administration (NHTSA) interpret your sketch to show the sidewall ending and the roof structure beginning at the point where the radius of curvature of the interior structure decreases sharply (see the point marked 'A' on the sketch). Since the shaded portion of your sketch falls below that point, it is considered part of the sidewall and need not comply with the head protection zone requirements.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam2230OpenMr. A. G. Colburn, Director of Trailer Design, Lufkin Industries, Inc., P.O. Box 848, Lufkin, TX 75901; Mr. A. G. Colburn Director of Trailer Design Lufkin Industries Inc. P.O. Box 848 Lufkin TX 75901; Dear Mr. Colburn: This responds to your February 6, 1976, questions whether Lufki Industries may, as an incomplete vehicle manufacturer, build 'incomplete chassis trailers' that do not have brakes installed that comply with Standard No. 121, *Air Brake Systems*, and whether Lufkin may tow the 'incomplete chassis trailers' over the highway to the final-stage manufacturer without brakes that conform to Standard No. 121.; Lufkin's activities are regulated by Part 568 of Title 49 of the Cod of Federal Regulations, if the 'incomplete chassis trailers' qualify as 'incomplete vehicles.' A copy is enclosed for your information. Part 568 does not require the incomplete vehicle to meet all applicable safety standards, but S 568.4 does require a statement of the status of an incomplete vehicle's conformity with all applicable standards.; In answer to your second question, the NHTSA permits the use of a incomplete vehicle on the public highways for the purpose of transit between the incomplete vehicle manufacturer and subsequent manufacturers, but for no other purpose, until such time as the vehicle complies with all Federal motor vehicle safety standards applicable to it as completed. This ruling by the NHTSA does not relieve the manufacturer or shipper from any applicable requirement imposed on the incomplete vehicle by other Federal, State, or local authority.; Sincerely, Frank Berndt, Acting Chief Counsel |
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ID: aiam4833OpenMr. A. Kling; Mr. A. Kling; "Mr. A. Kling Hamadbik, Ltd 16, Beit Alfa St. Tel-Aviv 67219 Israe Dear Mr. Kling: This responds to your inquiry about the color coding requirements in section S5.1.14 of Federal motor vehicle safety standard No. 116, Motor vehicle brake fluids. (49 CFR 571.116). After noting that DOT 3 and DOT 4 brake fluid must be colorless to amber, you asked what is the color coding range for amber. As explained below, the agency has decided not to specify a numerical or chromatic 'range' for the color coding requirements. Instead, the appropriate method for determining compliance to the color coding requirements is through visual inspection. The purpose of the color coding requirements is to permit easy identification of fluids before they are placed in a vehicle, in order to prevent the mixing of an incompatible fluid in a braking system. At one time, the National Highway Traffic Safety Administration (NHTSA) had proposed color requirements defined in terms of millimicrons. (38 FR 32142, November 21, 1973). However, when the agency later determined that visual inspection for color compliance was adequate, the proposed wavelength bands were deleted. (39 FR 30353, August 22, 1974) In a subsequent notice, the agency explained that The specifications for fluid colors are intended to refer to color ranges as generally interpreted in daylight by persons of normal color vision. No color coordinates are proposed, since the fluids may change color in storage or in use (without detriment to the performance of the fluids). (40 FR 56928, December 5, 1975) Thus, the generally interpreted meaning for 'amber' (which is defined as 'yellowish-brown' by the Random House Dictionary of the English Language) should be used to determine if a brake fluid complies with the color coding requirements for DOT 3 and DOT 4 brake fluid. I hope this information is helpful. If you have any further questions, please feel free to contact Marvin Shaw of my staff at this address or by telephone at (202) 366-2992. Sincerely, Paul Jackson Rice Chief Counsel"; |
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ID: aiam0523OpenLieutenant J. R. O'Donnell, Acting Commander, Regulation & Inspection Section, Department of California Highway Patrol, P. O. Box 898, Sacramento, CA, 95804; Lieutenant J. R. O'Donnell Acting Commander Regulation & Inspection Section Department of California Highway Patrol P. O. Box 898 Sacramento CA 95804; Dear Lieutenant O'Donnell: This is in reply to your letter of August 6, 1971, in which yo enclosed copies of drawings illustrating clearance and side marker lamps installed on several types of trucks and trailers in compliance with the requirements of the California Vehicle Code and asked for our advice as to whether there are any conflicts with the Federal requirements.; There are several such conflicts, and our comments follow: >>>1. *REQ BUL-3 SUPPLEMENT 1* (a) Page 2 - Standard No. 108 prescribes the general location o clearance lamps and side marker lamps without specifying tolerances. The first sentence of each of the paragraphs on clearance lamps and side marker lamps adequately reflect the Federal requirements. These general requirements of Standard No. 108 preempt the authority of a State to prescribe tolerances for alternate locations of the Lamps and subsequent sentences in these paragraphs which do so are improper.; (b) Page 3 - Figure 3, *Combination Clearance and Sidemarker Lamps* does not appear to properly illustrate the requirement that a clearance lamp be visible at an angle of 45 degrees to the right.; 2. *Truck tractors* (a) Statements appear frequently that front amber side marker lamps ar 'Not required on pre-1969 Tractors.' This is incorrect, front amber side marker lamps are required on any truck tractor 80 or more inches in overall width, manufactured on or after January 1, 1968.; (b) Various figures illustrate truck tractors with red rear clearanc and side marker lamps. It is unclear whether California requires truck tractors to be equipped with these lamps, or whether the figures illustrate acceptable mounting locations if a vehicle is so equipped. Standard No. 108 provides that truck tractors 'need not' be equipped with these lamps, therefore, California, under the preemption provisions of the Vehicle Safety Act, is not authorized to require them.; 3. *Clearance lamps* (a) The figures do not clearly illustrate whether the widest point o vehicles is the front fender or body (i.e. tank on tank trucks, flat bed on 'dromedary' trucks and flat bed trucks, van on van body trucks, body on utility trucks). If the body is the widest point of the vehicle, amber clearance lamps must be mounted there, but if the widest point is at the front fenders, the clearance lamps must be mounted at that location. No alternate locations are permissible, though shown in your figures, and in any event, cab-mounted clearance lamps are inappropriate whether single or combined with another lamp.; (b) The widest point of a horse trailer is the fender, and clearanc lamps must be mounted here, not on the body.; 4. *Logging dolly*. Logging dollies are 'pole trailers' for purposes o the Federal Motor vehicle safety standards and are specifically excluded from Standard No. 108. Therefore, we have no comments on California's requirements.; 5. *Boat trailers* (a) Clearance lamps are not required if the trailer is less than 8 inches wide.; (b) A combination clearance lamp (amber to front, red to rear) i permitted, if it is located atop the fender, as an alternative to separate amber and red clearance lamps.; (c) The required location of the front amber side marker lamp fo trailers (not shown on your figure) is 'as far to the front as practicable,' with a permissible location 'as far forward as practicable exclusive of the trailer tongue.'<<<; We are returning to you copies of the drawings you enclosed, marked t reflect our comments.; Sincerely, Lawrence R. Schneider, Chief Counsel |
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ID: aiam0489OpenMr. James Eckstein, 3025 St. Paul Street, Baltimore, Maryland 21218; Mr. James Eckstein 3025 St. Paul Street Baltimore Maryland 21218; Dear Mr. Eckstein: This is in reply to your letter of August 27, 1971, which was forwarde to this office October 20, 1971, by the Federal Trade Commission, regarding Government specifications for retreaded tires. You refer to problems you believe result from 'out of roundness,' specifically, abnormal wear and blowouts at normal boulevard and highway speeds. You wish to determine whether this problem results from 'too lenient' Government requirements, or whether 'manufacturers are negligent.'; Out-of-roundness can occur in a retreaded tire for numerous reasons and its presence does not necessarily indicate negligence on the part of the manufacturer. Moreover, while an out-of-round tire may affect vehicle handling it generally does not blow out at normal boulevard or even highway speeds, as result of the out-of-round condition. Thus, a blow out in an out-of-round tire could have resulted from other factors. Many tire dealers, in addition, have machines that can eliminate out-of-roundness by cutting of excess tread.; With reference to Federal regulations of retreaded tires, the firs such regulation will become effective January 1, 1972. This regulation, Motor Vehicle Safety Standard No. 117, 'Retreaded Pneumatic Tires,' specifies size and performance requirements for retreaded tires for use on passenger cars. There requirements are similar to those that have been applicable to new passenger car tires since January 1, 1968. None of these requirements specifically concern 'out-of-roundness.' We do not have evidence that this characteristic, by itself, is a safety problem.; Sincerely, Richard B. Dyson, Assistant 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.