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: aiam5522OpenMr. Robert E. Fouts President Earl's Performance Products 189 W. Victoria St. Long Beach, CA 90805; Mr. Robert E. Fouts President Earl's Performance Products 189 W. Victoria St. Long Beach CA 90805; "Dear Mr. Fouts: This responds to your question whether the whip tes specified in Federal Motor Vehicle Safety Standard No. 106, Brake Hoses, can be interpreted to permit a modification to the test apparatus to facilitate your brake hose's meeting the whip test. As explained below, the answer is no. You describe your brake hose as made of 'extruded teflon armored with stainless steel braid.' You state your brake hose can meet all Standard No. 106 test specifications except for the whip test (See S6.3). The whip test specifies fastening the brake hose on a test apparatus at two ends and cycling for 35 hours. You state because of 'aggravated cyclic stress,' your brake hoses fail before 35 hours. To prevent such failures, you wish to add a 'whip dampener,' a movable 'spherical bearing enclosed in a machined housing', to the brake hose. In addition to the two ends, the whip test apparatus will mount the brake hose at the 'whip dampener.' You wish to know whether the whip test can be interpreted to permit mounting the brake hose at the 'whip dampener.' In our opinion, S6.3 cannot be interpreted to permit mounting the brake hose at the 'whip dampener.' S6.3.1 Apparatus specifies a test apparatus that mounts the brake hose at 'capped end fittings' on one end and 'open end fittings' on the other, and specifies no mounting points in between. Thus, a test apparatus that mounts the brake hose at a 'whip dampener,' which is not an end fitting, would not meet Standard No. 106. However, the issues raised in your letter have led us to consider amending the whip test to permit the 'whip dampener' when testing steel braided brake hoses. Accordingly, we will initiate rulemaking to further consider the issues. I hope this information is useful. If you have any further questions, please contact Dorothy Nakama of my staff at (202) 366-2992. Sincerely, Philip R. Recht Acting Chief Counsel"; |
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ID: aiam1832OpenMr. E. J. Banks, The Glass Doctor, 10923 Indian Trail, Suite 109, Dallas, TX 75229; Mr. E. J. Banks The Glass Doctor 10923 Indian Trail Suite 109 Dallas TX 75229; Dear Mr. Banks: This is in reply to your letter dated January 29, 1975, asking whethe a product which you use to repair damaged windshields is prohibited by Federal law or regulation. Your letter was forwarded to our office by the NHTSA Regional Administrator in Fort Worth. You describe the repair process which you use as one in which the air in a damage spot or crack in the windshield is displaced by the product in a liquid form. As this product hardens it bonds itself to the glass, making the damaged area stronger than the other areas of the glass.; There are no Federal laws or regulations which prohibit the use of suc a material or process in the repair of windshields which have previously been installed in vehicles and damaged in use. Using such a material or process in a *new* (but damaged) windshield (such as in shipment) could cause the windshield to fail to meet the performance requirements of Motor Vehicle Safety Standard No. 205 (49 CFR S 571.205) and we would therefore discourage its use in new windshields.; We are pleased to be of assistance. Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam0720OpenMs. Donna M. Barnard, Owner, Scott's Trailer Market, 2020 E. Fremont Street, Las Vegas, NV 89101; Ms. Donna M. Barnard Owner Scott's Trailer Market 2020 E. Fremont Street Las Vegas NV 89101; Dear Ms. Barnard: This is in reply to your letter of May 10, 1972 to Mr. E.T. Drive requesting further clarification of the Tire Identification and Record Keeping regulations concerning your responsibility as a seller of trailer coaches.; The regulation does not distinguish between the responsibility o manufacturers, distributors and dealers of trailer coaches as opposed to manufacturers, distributors and dealers of other type vehicles. Therefore, a manufacturer of a trailer coach is required, pursuant to section 574.10 of the regulation, to maintain a record of tires shipped on or in the vehicle and the name and address of the purchaser of the vehicle. The manufacturer is free to use the tire identification system on the tire or any other system as long as the system would enable him to notify the purchaser of the vehicle in the event the tires the vehicle is equipped with become the subject of a recall. Therefore, in most cases, if the manufacturer obtains the name of the purchaser from the seller and is able to identify the tires on the vehicle, he is able to meet this requirement. The method the manufacturer uses to maintain a record of the tires on the vehicle appears to vary, but the efficiency of that record is the responsibility of the manufacturer.; On the other hand, if the vehicle dealer changes tires prior to th sale to the user, the manufacturer is no longer responsible for maintaining the record of the tires on the vehicle. In this case section 574.9(b) of the regulation would apply and the vehicle dealer would have to send the name and address of the purchaser of the vehicle, the tire identification number of the tire on the vehicle, and the dealer's name and address to the manufacturer of the tires.; For your convenience enclosed is a copy of the regulation. Sincerely, David Schmeltzer, Assistant Chief Counsel |
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ID: aiam1998OpenMr. Carl Morton, County of Los Angeles Road Department, 5530 West 83rd Street, Los Angeles, California 90045; Mr. Carl Morton County of Los Angeles Road Department 5530 West 83rd Street Los Angeles California 90045; Dear Mr. Morton: Please forgive the delay in responding to your letter of April 28 1975, concerning tires used on pull brooms.; Federal Motor Vehicle Safety Standard No. 119, *New pneumatic tires fo vehicles other than passenger cars*, (copy enclosed), specifies labeling and performance requirements for all tires designed for use on pull brooms. This standard applies to all such tires manufactured on or after March 1, 1975. There is presently no requirements, however, that vehicles be equipped with tires conforming to the standard. The National Highway Traffic Safety Administration has proposed and is considering the issuance of a new Standard No. 120, *Tire selection and rims for motor vehicles other than passenger cars*, which would require all new pull brooms manufactured after its effective date to be equipped with tires conforming to Standard No. 119.; Yours truly, Frank Berndt, Acting Chief Counsel |
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ID: aiam5172OpenMr. L. Schmidt 610 Fulton Street Seymour, WI 54165; Mr. L. Schmidt 610 Fulton Street Seymour WI 54165; "Dear Mr. Schmidt: Your letter requesting information about regulation that might affect substitution of a diesel engine for a 'worn out' gasoline engine has been referred to my office for reply. I apologize for the delay in answering. By way of background, NHTSA is authorized by the National Traffic and Motor Vehicle Safety Act (Safety Act) to issue Federal motor vehicle safety standards (FMVSS's) that set performance requirements for new motor vehicles and new items of motor vehicle equipment. NHTSA is not authorized to certify or approve motor vehicles or motor vehicle equipment for compliance with the FMVSS's. Instead, under the Safety Act, each manufacturer of a motor vehicle or item of motor vehicle equipment is responsible for certifying that its products meet all applicable safety standards. We do not have any requirements that would apply to the conversion of a vehicle from gasoline to diesel if the conversion is made by you on your own vehicle. The Safety Act and our regulations generally do not apply to a vehicle after the vehicle is sold to a consumer for purposes other than resale. Although the Safety Act prohibits certain entities from tampering with or removing federally required safety systems, the prohibition does not apply to modifications by a vehicle owner to his or her own vehicle. If the diesel engine were substituted for the gasoline engine by a vehicle manufacturer, distributor, dealer or repair business, the installer would not have to certify the vehicle as described above. Instead, 108(a)(2)(A) of the Safety Act requires any of these parties making the substitution to ensure that it did not knowingly render inoperative any device or system of design installed in compliance with any applicable safety standard, such as Standard 301, 'Fuel System Integrity' (49 CFR 571.301, copy enclosed). The purpose of Standard 301 is to reduce deaths and injuries occurring from fires that result from fuel spillage during and after motor vehicle crashes. 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 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. You also asked if any law forbade diesel conversions in zones within your state in which emissions tests are required. We suggest you contact the Environmental Protection Agency for any questions concerning emissions and air quality. The general telephone number for the EPA is (202) 382-2090. You should also contact the state of Wisconsin for emissions testing regulations. I hope this information is helpful. If you have any more questions about NHTSA's safety standards, please contact David Elias of my staff at this address or by telephone at (202) 366-2992. Sincerely, John Womack Acting Chief Counsel Enclosure"; |
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ID: aiam0370OpenMr. Yoshiyuki Mizuno, Engineering Representative, Nissan Motor Co., Ltd., Liaison Office in U.S.A., 400 County Avenue, Secaucus, NJ, 07094; Mr. Yoshiyuki Mizuno Engineering Representative Nissan Motor Co. Ltd. Liaison Office in U.S.A. 400 County Avenue Secaucus NJ 07094; Dear Mr. Mizuno: This is in reply to your letter of May 10, 1971, concerning coverin material for seats and door trim that is used solely to protect the interior of the vehicle during transportation from the manufacturer to the dealer. You have asked whether this covering material is required to comply with the flammability requirements of Standard No. 302.; Whether the material must comply with the standard depends upon whethe it is likely to be used in a significant number of cases by the purchaser as part of the motor vehicle. You have stated that the only purpose of the material is 'to insure the delivery of a car in which the interior is in good condition.' It is important that this intent be carried out in practice, if the material is not to be considered vehicle interior material subject to the standard. Two criteria which would be considered in determining whether the material is covered by the standard are (1) whether it is placed in the vehicle in a way that its use after purchase is unlikely, and (2) what steps the manufacturer has taken to see that it is removed before sale to the purchaser.; We cannot make a final determination as to whether such material mus meet the requirements without more information, particularly with respect to the questions noted above. However, if Nissan does take appropriate steps to ensure that such material will not be used as a seat cover by the purchaser, then the material would not be required to meet the requirements of the Standard.; We are pleased to be of assistance. Sincerely,Lawrence R. Schneider, Acting Chief Counsel |
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ID: aiam5488OpenMr. Scott E. Peters Director, Regulations & Compliance U.S. Electricar 5355 Skylane Boulevard Santa Rosa, CA 95403; Mr. Scott E. Peters Director Regulations & Compliance U.S. Electricar 5355 Skylane Boulevard Santa Rosa CA 95403; "Dear Mr. Peters: This responds to your letter to me in which you aske whether Federal Motor Vehicle Safety Standard (FMVSS) No. 110, Tire selection and rims (49 CFR 571.110), applies to your Electricar sedan. You explained that your Electricar sedan (Electricar), a converted Geo Prizm, is being built under NHTSA Exemption No. 92-3 for low-emission vehicles. You stated that the Electricar's speed and endurance limitations are substantially below those of internal combustion-powered vehicles. You further stated that it is your understanding that 'the purpose of Standard No. 110, S4.4.2 (I assume you meant paragraph S4.2.2, since there is no S4.4.2 in the standard) is to ensure against tire failure due to prolonged operation at speeds in the range of 75 mph or higher.' Thus, you interpret FMVSS No. 110 as not applying to the Electricar or other electric passenger cars 'in which it is physically impossible to operate at high speeds for an extended duration.' You asked this agency, therefore, to review paragraph S4.2.2 and provide you our opinion as to its applicability to your Electricar. As discussed below, the requirements of S4.2.2 are applicable to electric passenger cars. By way of background information, the National Highway Traffic Safety Administration issues safety standards for motor vehicles and motor vehicle equipment. The agency does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to certify that their vehicles and equipment meet applicable safety standards. Federal Motor Vehicle Safety Standard No. 110 specifies requirements for tire selection to prevent overloading. Section S2 of the standard provides that the standard applies to passenger cars. S4.2 of the standard specifies the following tire load limits: S4.2.1 The vehicle maximum load on the tire shall not be greater than the applicable maximum load rating as marked on the sidewall of the tire. S4.2.2 The vehicle normal load on the tire shall not be greater than the test load used in the high speed performance test specified in S5.5 of section 571.109 of that tire. The test load used in the high speed performance test specified in S5.5 of Standard No. 109 is 88 percent of the tire's maximum load rating as marked on the tire sidewall. With respect to your question whether S4.2.2 applies to electric passenger cars, the answer is yes. That section applies on its face to all passenger cars, and does not include an exception for electric passenger cars. Your understanding that the purpose of S4.2.2 is limited to ensuring against tire failure due to prolonged operation at speeds in the range of 75 mph or higher is incorrect. The reference in that requirement to Standard No. 109's high speed performance test is for the sole purpose of specifying a load and not to indicate that the requirement is limited to high speed operation. As indicated above, Standard No. 110 seeks to ensure that tires are not overloaded. One way Standard No. 110 does this is by requiring in S4.2.1 that the vehicle maximum load on the tire not exceed the maximum load rating of the tire. Another way Standard No. 110 does this is by limiting the vehicle normal load on the tire, so that the tire will have some reserve load carrying capacity available to handle safely cargo and other kinds of added loading the car may experience. S4.2.2 does this by limiting the normal load on a tire to 88 percent of the tire's maximum load rating, which ensures that 12 percent of the tire's load rating will be available to bear cargo and other added loads. I hope this information is helpful to you. Should you have any further questions or need additional information, please feel free to contact Walter Myers of my staff at this address or at (202) 366-2992. Sincerely, Philip R. Recht Chief Counsel Enclosure"; |
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ID: aiam1977OpenMr. H. Ray Cozad, FMC Corporation, Crane & Excavator Division, 1201 Sixth Street Southwest, Cedar Rapids, IA 52406; Mr. H. Ray Cozad FMC Corporation Crane & Excavator Division 1201 Sixth Street Southwest Cedar Rapids IA 52406; Dear Mr. Cozad: This responds to FMC Corporations' June 23, 1975, request fo clarification of a recent NHTSA proposal (40 FR 24915, June 11, 1975) to amend Standard No. 121, *Air brake systems*, to establish an exemption criterion for a vehicle that has an 'unloaded vehicle weight that is not less than 95 percent of the vehicle GVWR gross vehicle weight rating '. You ask whether a vehicle's 'unloaded weight' means the GVWR, as established by adding the gross axle weight ratings (GAWR) of all axles, minus whatever portions of the vehicle are removed for highway travel.; The answer to your question is no. In light of the requirements fo GVWR in Part 567.4 (Certification), unloaded vehicle weight will normally be the GVWR of the vehicle minus its rated cargo load and its assigned occupant weight (at least 150 lbs). The rated cargo load would not include the weight of portions of a vehicle which are essential to its specialized function but are removed in accordance with State regulation for transit purposes.; I would also note that the NHTSA definition of GVWR (49 CFR S 571.3 does not require that the GVWR be the sum of the vehicle's GAWR's. Of course the GVWR must not exceed the sum of vehicle GAWR's.; With regard to your June 17, 1975, suggestion of a meeting with Mr Larson, I would prefer first to have your view of these clarifications.; Yours truly, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam0665OpenMr. R. E. Kennel, Manager, Technical Services, The Budd Company, Automotive Division, Detroit, MI 48215; Mr. R. E. Kennel Manager Technical Services The Budd Company Automotive Division Detroit MI 48215; Dear Mr. Kennel: This is in reply to your letter of March 10, 1972, in which yo presented a series of questions concerning the meaning of several requirements of Federal Motor Vehicle Safety Standard No. 121, 'Air Brake Systems.' Our reply deals with the questions in the order you asked them.; >>>1. Your first question concerns the meaning of the statement i section S5.4 that 'a brake assembly that has undergone a road test pursuant to S5.3 need not conform to the requirements of this section.' To parahprase (sic) your question, the quoted language means that if a given brake assembly is subjected to the road test, the same brake assembly with the used lining need not conform to the dynamometer requirements. Conformity to the dynamometer requirements will be determined by testing an identical brake assembly with new linings. The petitions for deletion of dynamometer testing would have made the road test the only test. The standard requires both tests, even though two sets of identical brakes will be used, and our statement that the petitions were denied is therefore correct.; 2. You point out that the measurement interval used in S5.4.1.1 fo determining average torque, which begins when a specified pressure is reached, differs from the interval specified in S5.4 for measuring deceleration, which begins with the onset of deceleration. Although we agree that you may need different instrumentation for measuring average torque and average deceleration, we do not agree that their is any conflict since average torque and average deceleration are not required to be measured at the same time. We consider the present method of measuring torque and deceleration to be the correct methods.; 3. The typographical error in section S5.4.1.1, which you hav correctly edited to read 'Repeat the procedure six times, increasing the brake chamber air pressure by 10 psi each time,' has been corrected by a revision in the March 29, 1972, *Federal Register*.; 4, 5, 6. The requirements of S5.4.2, S5.4.2.1 and S5.4.3 concernin average deceleration rates should not be understood to mean that a manufacturer, in his own testing, must test at exactly that rate. It is advisable for him to test in a manner that offers assurance that the brakes will pass when tested in the manner specified in the standard. Typically, where a test value such as 9 fpsps is specified, manufacturers tend to use more adverse values in their own testing. Under the former wording of these sections, the compliance agency could have tested brakes at decelerations higher than the specified minimum, and it would have been much more difficult for a manufacturer to ascertain his 'worst case' situation.<<<; The notice ofoposing (sic) to amend the weight conditions fo truck-tractors should be issued within the next two months.; Sincerely, E. T. Driver, Director, Office of Operating Systems, Moto Vehicle Programs; |
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ID: aiam2658OpenMr. Bernhard Schwartz, Sales Manager, Sate-Lite Mfg. Co., 4600 North Olcott Avenue, Harwood Heights, Illinois 60656; Mr. Bernhard Schwartz Sales Manager Sate-Lite Mfg. Co. 4600 North Olcott Avenue Harwood Heights Illinois 60656; Dear Mr. Schwartz: This responds to your August 2, 1977, letter asking whether you ca submit to the National Highway Traffic Safety Administration (NHTSA) a piece of your equipment for confirmation that it complies with Standard No. 125, *Warning Devices*.; The NHTSA does not issue advance approvals of equipment or moto vehicles manufactured in accordance with the safety standards. It is the responsibility of each manufacturer of motor vehicles or equipment to ensure that his motor vehicle or equipment complies with the requirements. Therefore, it is not necessary for you to submit your design to the NHTSA prior to its production.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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Request an Interpretation
You may email your request to Interpretations.NHTSA@dot.gov or send your request in hard copy to:
The Chief Counsel
National Highway Traffic Safety Administration, W41-326
U.S. Department of Transportation
1200 New Jersey Avenue SE
Washington, DC 20590
If you want to talk to someone at NHTSA about what a request for interpretation should include, call the Office of the Chief Counsel at 202-366-2992.
Please note that NHTSA’s response will be made available in this online database, and that the incoming interpretation request may also be made publicly available.