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: aiam3753OpenMr. Karl-Heinz Ziwicka, Manager, Safety & Emission Control Engineering, BMW of North America, Inc., Montvale, NJ 07645; Mr. Karl-Heinz Ziwicka Manager Safety & Emission Control Engineering BMW of North America Inc. Montvale NJ 07645; Dear Mr. Ziwicka: This is in reply to your letter of August 15, 1983, asking for a interpretation of Federal Motor Vehicle Safety Standard No. 108 with respect to spacing of turn signal lamps on motorcycles.; As you have noted, SAE Standard J588e is the basic Federal requiremen for turn signal lamps referenced by Tables I and III of Standard No. 108 for all motor vehicles. One of the requirements of J588e is that the front turn signal must be separated from the low beam headlamp by at least 4 inches measured from the filament center of the turn signal to the inside diameter of the retaining ring of the low beam headlamp. But, as you further point out, paragraph S4.3.1.7 of Standard No. 108 relieves this restriction under certain circumstances. However, because Table IV of Standard No. 108 specifically requires a minimum edge to edge separation distance of 4 inches between the turn signal lamp and the headlamp on a motorcycle, you believe that it is unclear whether S4.3.1.7 relieves this restriction also, and have asked us for an interpretation that it does.; We are unable to provide the interpretation that you seek. True, SA J588e does incorporate a spacing restriction which is relieved by S4.3.1.7 under certain circumstances. However, although the requirements of J588e generally do apply to motorcycle turn signal lamps, the spacing restriction does not apply, having been superseded by the specific language in Table IV addressed to motorcycles. We believe that it is important to maintain a minimum edge to edge distance on motorcycles that exceeds the minimum allowable on other motor vehicles, in order to assure that the conspicuity of the turn signal will not be masked by the headlamp beam. Because the motorcycle headlamp beam is not fixed in relation to the road as an automobile headlamp is, its vertical and horizontal aim will change with the lean angle and the steering angle of the machine. The higher intensity portions of the beam will rise above the horizontal, thus producing more glare and reducing the conspicuity of the turn signal. Further, given the almost universal daytime use of headlamps, the lesser conspicuity of the turn signal on motorcycles during daylight hours must not be compromised.; I hope that this answers your question. Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam2841OpenMr. Robert Hoppe, 1436 So. Sherman Street, Longmont, CO 80501; Mr. Robert Hoppe 1436 So. Sherman Street Longmont CO 80501; Dear Mr. Hoppe: This responds to your letter of May 3, 1978, in which you request determination as to whether the three- wheeled motor vehicle which you are designing is a 'motorcycle' or an automobile ('passenger car') for purposes of complying with federal motor vehicle safety standards.; The vehicle falls within the definition of 'motorcycle' set forth i regulations under the National Traffic and Motor Vehicle Safety Act of 1966:; >>>'Motorcycle' means a motor vehicle with motive power having a sea or saddle for the use of the rider and designed to travel on not more than three wheels in contact with the ground. (49 CFR Part 571.3(b))<<<; Accordingly, the vehicle would have to meet the requirements of safet standards applicable to motorcycles. I have enclosed an information sheet explaining where you can obtain federal standards and regulations.; I want to point out that in April 1974, this agency proposed a revisio of the above definition of 'motorcycle' under which this term would be limited to two-wheeled motor vehicles and to three-wheeled motor vehicles with handlebars and no passenger enclosures. I have enclosed a copy of this proposal. However, in view of the time that has elapsed since the proposal was issued, the agency has decided not to issue a final rule on this subject without providing another opportunity to comment.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam1294OpenL.E. Haight, Esq., Attorney at Law, 805 Idaho Street, P.O. Box 2777, Boise, ID 83701; L.E. Haight Esq. Attorney at Law 805 Idaho Street P.O. Box 2777 Boise ID 83701; Dear Mr. Haight: This is in reply to your letter of September 21, 1973, concerning you desire to disconnect the interlock system on your new car.; The dealer who sold you the car was required to have the interloc working at the time of sale pursuant to section 108(a)(1) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1397(a)(1)). However, section 108(b)(1) of the Act (15 U.S.C. 1397(b)(1)), provides that the requirements of 108(a)(1) do not apply after the first purchase of the vehicle for purposes other than resale. As a purchaser who intends to use the vehicle, you are therefore not subject to the requirements of the Act and may disconnect the interlock.; Despite the absence of legal sanctions for disconnecting the interlock we would hope that you could find a way to adjust the belt so that it could be worn without aggravating your bursitis. The physical sanctions for an unbelted person in a crash can be serious indeed.; Sincerely, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam3303OpenMr. Thomas P. McAskin, Kelsey-Hayes Company, Romulus, MI 48174; Mr. Thomas P. McAskin Kelsey-Hayes Company Romulus MI 48174; Dear Mr. McAskin: This responds to your December 7, 1979 letter to Docket No. 79-03 Notice 2 on Heavy Duty Vehicle Brake Systems. That letter was in part a comment to the docket and in part a request for an interpretation of Standard No. 121, *Air Brake Systems*. The points raised in your comment to the docket will be considered in our final rule on the issues proposed in Notice 2. This letter responds to your interpretive question whether your trailer emergency valve is permitted in accordance with the requirements of section 5.2.1.1 of the standard. The answer to your question is no.; Section 5.2.1.1 of the standard requires that vehicles be equipped wit a reservoir that is capable of releasing the parking brakes when the air in the service brake system fails. The valve that you suggest would not provide such a reservoir but would merely reroute air from the trailer air supply system which would be used to release the parking brakes. The agency does not believe that this complies with the requirement that a reservoir be provided.; Recently, the Berg Manufacturing Company has petitioned the agency t amend the standard in a manner that would permit the type of system that you suggest. The agency is now evaluating that petition and will issue a notice in the near future addressing this issue. We suggest that you closely follow this rulemaking action.; Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam2142OpenInterps. file, Parts 575.104(d)(1)(ii) and 575.6; Interps. file Parts 575.104(d)(1)(ii) and 575.6; Office visit by Pat Raher, Hogan and Hartson I received an office visit on December 8, 1975, from Mr. Raher of Hoga and Hartson (representing Mercedes-Benz). He showed me a sample information sheet of the type that Mercedes proposes to use to indicate the quality grades of tires with which its vehicles are equipped. We discussed the vehicle manufacturer's information requirement of the Uniform Tire Quality Grading Standards, and I indicated that a formal interpretation would follow our receipt of his letter, which is en route.; Mark I. Schwimmer, Attorney- Advisor |
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ID: aiam4995OpenMr. Gonshiro Miyoshi Manager, Design Administration Dept. Technical Division Ichikoh Industries, Inc. 80 Itado, Isehara-City Kanagawa, 259-11 Japan; Mr. Gonshiro Miyoshi Manager Design Administration Dept. Technical Division Ichikoh Industries Inc. 80 Itado Isehara-City Kanagawa 259-11 Japan; Dear Mr. Miyoshi: This responds to your letter of April 6, 1992, askin for an interpretation of Standard No. 108. With respect to a headlamp system consisting of two lamps, each containing two light sources, you have asked 'Is it permissible to have the bulb center of the lower beam lower than that of the upper beam (maximum height difference is 10mm) if they are arranged horizontally?' Paragraph S7.5(d)(2) specifies the manner in which 'the lower and upper beams of a headlamp system consisting of two lamps, each containing either one or two light sources, shall be provided . . .' In such headlamps where each light source provides a beam, the lower beam is provided 'by the outboard light source (or upper one if arranged vertically),' and the upper beam is provided 'by the inboard light source (or the lower one if arranged vertically).' Although the standard could be presumed to contemplate that two light sources within a headlamp would be located on the same horizontal or vertical plane, there is no specific requirement for light source placement. Because the difference in the horizontal mounting planes for bulb centers in your design is only 10mm, this difference is not sufficient to conclude that the light sources are vertically arranged, thus requiring that the lower beam bulb center be the 'upper' one, or on a plane that is higher. However, for your design to be permissible, the lower beam in this essentially horizontal array must be provided by the outboard light source in the headlamps as specified in S7.5(d)(2). Sincerely, Paul Jackson Rice Chief Counsel; |
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ID: aiam0485OpenMr. E. M. Ryan, Chief Design Engineer, Ward School Bus Mfg., Inc., P. O. Box 849, Conway, AR, 72032; Mr. E. M. Ryan Chief Design Engineer Ward School Bus Mfg. Inc. P. O. Box 849 Conway AR 72032; Dear Mr. Ryan: Your letter of October 28, 1971, to Mr. Stan Haranski, Truck Body an Equipment Association, Inc., concerning switching arrangements for school bus red signal lamps, has been forwarded to this Office for reply.; Paragraph S4.1.4(a) of Federal Motor Vehicle Safety Standard No. 10 requires that the four red signal lamps be controlled by a manually actuated switch. A two-way switch, whereby all four lamps are activated when the switch is in one position, and the two rear lamps only are activated when the switch is in the opposite position, would not be in violation of this requirement of Standard No. 108.; Sincerely, E. T. Driver, Director, Office of Operating Systems, Moto Vehicle Programs; |
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ID: aiam2512OpenMr. Raymond Titsworth, Project Engineer, Ward School Bus Mfg., Inc., P. O. Box 849, Highway 65 South, Conway, AR 72032; Mr. Raymond Titsworth Project Engineer Ward School Bus Mfg. Inc. P. O. Box 849 Highway 65 South Conway AR 72032; Dear Mr. Titsworth: This responds to your December 7, 1976 and January 8, 1977, question whether 53 described intersections of bus body components qualify as 'body panel joints' subject to the requirements of Standard No. 221, *School Bus Body Joint Strength*. This also responds to your question whether the seating reference point in Standard No. 222, *School Bus Passenger Seating and Crash Protection*, can be located using nominal seat cushion deflection.; The terms which establish the applicability of the requirements of th standard to a particular section of a school bus body are defined in S4 of the standard. Read together, they establish the following test. If the edge of a surface component (made of homogeneous material) in a bus that encloses the bus' occupant space comes into contact or close proximity with any other body component, the requirements of S5 apply, unless the area in question is designed for ventilation or another functional purpose or is a door, window, or maintenance access panel. Applying this test to the 53 intersections of bus body components you describe, it appears that the areas corresponding to the following numbered paragraphs of your letter are bus body joints and therefore must meet the 60-percent joint strength requirements: 1 through 34, 36, 37, 39, 42, 44, 45, 46, 51. Additionally the joint described in your January 8, 1977, submission must comply with the standard.; The illustration accompanying paragraph 16 shows a second joint betwee a door post and exterior trim panel with the notation that this joint is 'Not Required To Meet Std.' The agency concludes that this joint also must meet the requirements of the standard, because it is a connection of a body component with a body panel that encloses occupant space.; The lower skirt section described in paragraph 35 is not a body pane that encloses occupant space, because it is located entirely below the level of the floor line and, therefore, is excluded from the standard's requirements.; In the control console area, the interior side panel described i paragraph 38 and the shoulder cap (wire cover) described in paragraph 43 are considered maintenance access panels, whose joining with the bus body is excluded from the requirements only if a wire is installed behind them.; The turn signal housings described in paragraphs 40 and 41 are no considered to have a function in enclosing the occupant space and are therefore not considered body components for purposes of the requirements.; The front and rear headers described in paragraphs 47 and 48 ar considered primarily structural and have only an incidental role in enclosing the occupant space and, therefore, are not considered 'body panels' for purposes of the requirements.; The rubrail described in paragraph 49 is not considered to have function in enclosing the occupant space and, therefore, is not considered a body component for purposes of the requirements. For purposes of testing the complex joints to which it is fastened, it should be modified as necessary to prevent it from affecting testing of the underlying joint.; Because the plywood described in paragraph 50 is attached to a floo panel and is only added to some buses for insulation purposes, it is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.; The NHTSA concludes that parts A, E, and F of paragraph 52 describ joints between maintenance access panels and the bus body. The heater ducts in parts B, C, and D are the type of ventilation space that is not subject to requirements for joint strength.; In response to your question concerning the effect of seat cushio deflection on the location of the seating reference point, the NHTSA has determined that the definition of seating reference point contemplates some deflection of seat cushions to simulate compression of padding material under the weight of a human torso and thigh. As noted in the preamble of the second proposal for a school bus seating standard (39 FR 27585, July 30, 1974), 'It can be seen that the manufacturer's freedom to locate the point is sharply restricted by the definition which specifies that it actually simulate the position of the pivot center of the human torso and thigh, following SAE placement procedures.' However, since the seating reference point is an approximation of the pivot center, the NHTSA permits the manufacturer to locate the point based upon nominal seat cushion deflection.; Sincerely, Frank A. Berndt, Acting Chief Counsel |
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ID: aiam5238OpenMr. Sam C. Nigro Bus Product Manager Webasto Thermosystems 1598 E. Lincoln Madison Heights, MI 48071; Mr. Sam C. Nigro Bus Product Manager Webasto Thermosystems 1598 E. Lincoln Madison Heights MI 48071; "Dear Mr. Nigro: This responds to your letter about auxiliary heater fueled by compressed natural gas (CNG) and liquid natural gas (LNG) for installation on buses using those alternative fuels. You stated that your company currently manufactures auxiliary heaters for diesel fueled buses, and is interested in developing heaters that would 'burn CNG and LNG same as the engine.' In a telephone conversation with Marvin Shaw of my staff, you explained that you would like information about NHTSA's current requirements for auxiliary heaters on alternative fueled buses and the agency's future plans in this area. I am pleased to have this opportunity to explain our regulations to you. By way of background information, NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act (Safety Act, 15 U.S.C. 1381, et seq.), it is the responsibility of the manufacturer to ensure that its motor vehicles or equipment comply with applicable Federal motor vehicle safety standards (FMVSS's). The following represents our opinion based on the facts provided in your letter. NHTSA does not have any safety standards specifically covering auxiliary heaters of any kind, and I am not aware of any plans to issue standards in this area. Nevertheless, an auxiliary heater is an item of motor vehicle equipment. As a manufacturer of motor vehicle equipment, you are subject to the requirements in 151-159 of the Safety Act concerning the recall and remedy of products with defects relating to motor vehicle safety. If you or NHTSA determines that a safety-related defect exists, you must notify purchasers of your product and remedy the problem free of charge. (This responsibility is borne by the vehicle manufacturer in cases in which the heater is installed on a new vehicle by or with the express authorization of that vehicle manufacturer.) Any manufacturer that fails to provide notification of or remedy for a defect may be subject to a civil penalty of up to $1,000 per violation. As Mr. Shaw informed you on the telephone, earlier this year NHTSA proposed to issue a safety standard that would apply to CNG tanks (i.e., containers designed to store CNG as motor vehicle fuel on-board a motor vehicle) and vehicles using CNG as a fuel (58 FR 5323, January 21, 1993). If this proposed standard is adopted, it would affect your product in the following manner. If your heater were installed as original equipment on a new vehicle, the vehicle manufacturer is required by our certification regulations to certify that the entire vehicle (with your product installed) satisfies the requirements of all applicable FMVSS's, including the CNG fuel system standard. If the heater were added to a new, previously-certified vehicle (e.g., a new completed bus), the person who adds the system would be required to certify that, as altered, the vehicle continues to comply with all of the safety standards affected by the alteration. These certification requirements apply to the vehicle manufacturer and alterer regardless of whether the heater is connected to the vehicle's fuel system. Of course, if the heater is connected to the vehicle's fuel system, the vehicle's compliance with the CNG standard should be carefully scrutinized. If the heater were installed on a used vehicle by a vehicle manufacturer, distributor, dealer or repair business, the installer would not be subject to the certification requirements outlined above. Instead, the installer would have to ensure that it did not knowingly render inoperative the compliance of the vehicle with any applicable safety standard, including the CNG standard. This is required by 108(a)(2)(A) of the Safety Act. If the modification of the vehicle entailed connecting the heater to the vehicle's fuel system, compliance with the CNG standard would be especially germane to whether 108(a)(2)(A) were violated. The prohibition of 108(a(2)(A) does not apply to individual vehicle owners who alter their own vehicles. Thus, under our requirements, individual owners may install any item of motor vehicle equipment regardless of its effect on compliance with the FMVSS's. However, NHTSA encourages vehicle owners not to tamper with vehicle safety equipment if the modification would degrade the safety of the vehicle. The certification responsibilities discussed above would affect vehicle manufacturers even if the proposed CNG standard is not adopted or is not yet effective when you market your product. Except for FMVSS 301, which sets fuel system integrity requirements for gasoline and diesel-powered buses under 10,000 pounds GVWR, all of the FMVSS's that apply to a diesel- or gasoline-powered vehicle now apply to a CNG-powered vehicle. A manufacturer of a CNG-powered vehicle who installs your heater as original equipment must certify the vehicle to those standards, regardless if the CNG FMVSS is among them. Similarly, a vehicle alterer would have to certify that the vehicle, as altered, complies with all applicable FMVSS's. The 'render inoperative' prohibition would also apply even in the absence of a CNG FMVSS. The commercial entity listed in 108(a)(2)(A) who installs the heater on a CNG-powered vehicle would have to ensure that it did not knowingly render inoperative the compliance of the vehicle with any FMVSS that applies to the vehicle, even if a CNG standard is not among them. I am enclosing for your information a copy of NHTSA's proposed FMVSS for CNG tanks and vehicles. Also enclosed is a fact sheet titled Information for New Manufacturers of Motor Vehicles and Motor Vehicle Equipment, and a booklet entitled Federal Motor Vehicle Safety Standards and Regulations. As you are aware, the Federal Highway Administration has issued a regulation applicable to heaters on commercial vehicles. (49 CFR 393.77). You can contact the FHWA for an interpretation of its regulations at the following address: Theodore McConnell Chief Counsel Federal Highway Administration 400 7th Street, SW Washington, D.C. 20590 I hope this information is helpful. Please feel free to contact Marvin Shaw at this address or by telephone at (202) 366-2992 if you have any further questions or need additional information. Sincerely, John Womack Acting Chief Counsel Enclosure"; |
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ID: aiam2007OpenMr. Fred Long, South Texas Tire Test Fleet, Drawer J, Devine, TX 78016; Mr. Fred Long South Texas Tire Test Fleet Drawer J Devine TX 78016; Dear Mr. Long: This is to confirm your telephone conversation of July 31, 1975, wit Mark Schwimmer concerning the treadwear test procedures specified in 49 CFR Part 575.104, *Uniform Tire Quality Grading Standards* (UTQGS).; You had previously pointed out that the A78-13 and other tires ar available neither as original equipment nor as recommended replacement options on any 1975 model passenger cars, although they are available as replacement options for the 1974 Ford Pinto. You had asked whether it is permissible for a tire manufacturer to conduct treadwear testing for such tires on a 1975 Pinto, in light of the National Highway Traffic Safety Administration's (NHTSA) statement that; >>>tires will be tested for compliance only on vehicles for which the are available as original equipment or recommended replacement options. (40 FR 23076, May 28, 1975)<<<; As Mr. Schwimmer explained to you, the UTQGS rules does not dictate th method by which a tire manufacturer must conduct his testing to assign grades. It merely specifies the procedures which the NHTSA will follow when testing tires for compliance with the rule. While the surest way for the tire manufacturer to be confident of compliance would be to follow these procedures in every detail, he is not legally obligated to do so. His obligation is simply to ensure that, when tested by the NHTSA according to the specified procedures, his tires are capable of achieving the grades which he has assigned to them. He may fulfill this obligation by whatever means he believes reliable and necessary. Thus, for example, he might choose a 1975 Pinto to test an A78-13 tire, if he is confident that the model year change in the Pinto will have no effect on the tire's treadwear performance. This decision is his, however. The NHTSA, in its compliance testing, would test such a tire on a 1974 Pinto or on some other passenger car for which it is original equipment or a recommended replacement option.; Sincerely, Frank Berndt, 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.