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: aiam1829OpenHonorable Mark Andrews, House of Representatives, Washington, DC 20515; Honorable Mark Andrews House of Representatives Washington DC 20515; Dear Mr. Andrews: This responds to your February 18, 1975, request for information i behalf of a constituent, concerning any Federal regulation which might require bulk oil trucks to have a 120-inch wheelbase and be equipped with certain wheels, tires, and axles.; Neither the National Highway Traffic Safety Administration (NHTSA) no the Bureau of Motor Carrier Safety of the Federal Highway Administration has issued a safety standard which requires a certain wheelbase or the components listed by your constituent.; NHTSA has issued Standard No. 121, *Air brake systems*, whic establishes minimum performance requirements for air-braked vehicles. A major requirement is that an air-braked vehicle must be capable of stopping within a distance that is comparable to average passenger car performance. This requirement is intended to reduce the incompatibility in braking performance between heavy trucks and passenger cars which must share the nation's highways.; Manufacturers are free to choose any design which permits thei vehicles to stop in the required distance. It is possible that the manufacturer of your constituent's vehicle has found that a longer wheelbase and stronger axles, brakes, wheels, and tires are necessary to insure that the vehicle is capable of consistently stopping without loss of control in a distance comparable to the average passenger car. We consider the modification of vehicles in this fashion to be a significant contribution to motor vehicle safety.; Sincerely, James C. Schultz, Chief Counsel |
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ID: aiam2850OpenMr. H. J. T. Young, Vice President - Technical Affairs, Cibie Corporation, 725 South Adams Road, Suite 209, Birmingham, MI 48011; Mr. H. J. T. Young Vice President - Technical Affairs Cibie Corporation 725 South Adams Road Suite 209 Birmingham MI 48011; Dear Mr. Young: This is in belated reply to your letter of December 15, 1977 requesting an interpretation of Federal Motor Vehicle Safety Standard No. 108, *Lamps, Reflective Devices and Associated Equipment*. Your request concerned the legality of installation on motor vehicles of remote manual or of automatic headlamp aiming equipment.; If a headlamp assembly meets the requirements of Standard No. 108 whe installed with or without auxiliary means of aiming, we consider the assembly to be in conformance. Your device does not appear to impair the effectiveness of the required lighting equipment within the prohibition of S4.1.3, and either device that you described would apparently provide an additional safeguard against glare when the rear of the vehicle is heavily loaded.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam2474OpenHonorable Albert H. Quie, House of Representatives, Washington, D.C. 20515; Honorable Albert H. Quie House of Representatives Washington D.C. 20515; Dear Mr. Quie: This is in reply to your letter of December 15, 1976, regarding complaint by Mr. Russ Fink, that tires marked within a certain size classification are not uniform.; Mr. Fink's letter does not report any actual tire dimensions and doe not fully explain the age of his tires, the amount of treadwear, the type of tread pattern, inflation pressures, and the width of the rims when he was making his measurements. All of these factors have an effect on tire size matching, and must be considered in making dimensional comparisons.; Contrary to Mr. Fink's claim, tire manufacturing is carefull controlled to meed rigid dimensional requirements. These requirements are a part of our Federal Motor Vehicle Safety Standards (FMVSS) No. 109 for new passenger car tires, No. 119 for other new motor vehicle tires, and No. 117 for retreaded passenger car tires. A copy of each is enclosed . Every effort is made in our standards enforcement program to assure that manufacturers and retreaders comply with the specified dimensional requirements.; Referring to the tables in Appendix AS of FMVSS No. 109, Mr. Fink ca see that there are differences is specifications for the three tires he mentions:; Tire Rim Max. Load Section Min. Size Size Width at 24 psi Width Facto H78-15 6'' 1450 8.55 36.50 7.60-15 5-1/2'' 1450 7.90 36.05 8.55-15 6'' 1510 8.45 36.57; In purchasing new or retreaded tires from a tire dealer, consumers ar entitled to dimensions held within specified tolerances, and when tires are found to exceed these tolerances we would appreciate being notified so that we may initiate investigation.; Sincerely, John W. Snow, Administrator |
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ID: aiam1289OpenMr. T.J. Wagner, 1409-119th Street, Whiting, Indiana 46394; Mr. T.J. Wagner 1409-119th Street Whiting Indiana 46394; Dear Mr. Wagner: #This is in reply to your letter of September 18 1973, concerning you recent purchase of tires that were marked 'Blemtube type must use tube,' but which were installed on your car without tubes. #The NHTSA does consider the mounting of 'tube type' tires without to involve at least a potential violation of the National Traffic and Motor Vehicle Safety Act. However, the establishment of a violation by the agency involves the purchase and testing of new tires, a time-consuming and costly process. The agency would not, moreover, under its authority, be able to take any action with respect to the tires sold to you. We will, however, inquire into the matter by contacting the dealer who sold you the tires in the hope that we may prevent a recurrence of the problem. #Thank you for bringing this matter to our attention. #Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicle Programs; |
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ID: aiam2907OpenMr. W. G. Milby, Manager, Engineering Services, Blue Bird Body Company, P. O. Box 937, Fort Valley, GA (sic); Mr. W. G. Milby Manager Engineering Services Blue Bird Body Company P. O. Box 937 Fort Valley GA (sic); Dear Mr. Milby: This responds to your September 20, 1978, letter asking whether particular bus body joint is subject to the requirements of Standard No. 221, *School Bus Body Joint Strength*. The joint in question is the connection of two body panels under which runs a continuous body member for the entire length of the bus body.; Standard No. 221 establishes strength requirements for body pane joints which are defined as 'the area of contact or close proximity between the edges of a body panel and another body component...' Body panel is further defined to mean 'a body component used on the exterior or interior surface to enclose the bus' occupant space.' The exterior body panels to which you refer are involved in the enclosure of the bus' occupant space, and accordingly, their connection is a joint falling within the requirements of the standard. The fact that an underlying body member runs under the panels perpendicular to the joint in no way excepts the joint from the requirements of the standard.; Your analogy of these panels to rub rails whose joints are not teste according to the requirements of the standard is inappropriate. Rub rails are added on to the exterior of a bus over the body panels. All parts of the rub rails fall outside the exterior skin of a bus, and therefore, they serve no purpose in enclosing occupant space. The panels to which you refer, on the other hand, are the primary sidewall components enclosing bus' occupant space.; You ask how the agency will test this joint since it has a bod structure member that runs perpendicular to it. You suggest that the agency cut an appropriate size specimen of the panels, joint, and underlying body member and pull one panel and the body member against the other panel and the body member. The agency disagrees. This procedure would not test the strength of the joint, since the stresses imposed by the test would be carried by the continuous body member being pulled against itself.; The agency tests such joints by cutting a specimen of the panels tha includes a portion of the underlying body member. The ends of the body member are then removed to allow the testing device to clamp the two body panels that are to be tested. However, rivets or other bonding materials that connect the panels and the body member at the joint remain intact. This is what is intended by the standard's requirement that the underlying body structure be included within the joint strength test. Leaving the underlying structure intact at the joint permits a test of the joint's strength that closely approximates the actual strength of the joint as it is installed in a completed bus.; Responding finally to your last comment that the agency by its testin technique is hindering the development of integrally constructed bodies, the NHTSA disagrees. The agency believes that the strength of the entire bus body is dependent upon the strength of its parts. Each joint must be examined independently to ensure that it is strong enough to withstand accident forces. Since those forces vary with the nature of any impact and can result in severe stress on one small section of a bus, it is appropriate to measure the strength of individual joints. However, the agency's testing technique as outlined above considers the effect of the underlying bus structure thus encouraging the development of integrally constructed bodies.; Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam0035OpenMr. William F. Knapp, 2358 Barksdale Boulevard, Bossier City, LA 71010; Mr. William F. Knapp 2358 Barksdale Boulevard Bossier City LA 71010; Dear Mr. Knapp: This letter confirms the discussion which took place during your visi to the Bureau on September 18, between yourself and Mr. Risteen of my staff, concerning the requirements of Federal Motor Vehicle Safety Standard No. 206 as related to aftermarket door lock installations.; Since Standard No. 206 does not apply to aftermarket installations, yo may continue to sell your special locking arrangement to State Police and private individuals without violating that Standard. It is suggested, however, that you check your State auto inspection laws to make sure there is no conflict with State regulations.; In response to your request, Mr. Risteen reviewed the test repor contained in your Automotive Safety Door Lock brochure. According to the report, the longitudinal and transverse loads which your locking assembly withstood were considerably higher than that required by Standard No. 206. However, the testing company did not certify that your locking device met the requirements of this Standard.; Sincerely, George C. Nield, Acting Director, Motor Vehicle Safet Performance Service; |
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ID: aiam4737OpenMr. Keith D. Kroll Vice President, Engineering Hehr International, Inc. 3333 Casitas Ave P.O. Box 39160 Los Angeles, CA 90039-0160; Mr. Keith D. Kroll Vice President Engineering Hehr International Inc. 3333 Casitas Ave P.O. Box 39160 Los Angeles CA 90039-0160; "Dear Mr. Kroll: This is in response to your request for a interpretation of S5.5.1 and S5.5.2 of Standard No. 217, Bus Window Retention and Release (49 CFR 571.217). More specifically, I understand your request to refer to buses that are not school buses and that have a gross vehicle weight rating of more than 10,000 pounds. For such buses, S5.5.1 of Standard No. 217 provides that: '... each emergency door shall have the designation 'Emergency Door' or 'Emergency Exit' ... followed by concise operating instructions describing each motion necessary to unlatch and open the exit, located within 6 inches of the release mechanism.' S5.5.2 requires that emergency exit 'markings' be visible to occupants in specified locations, under lighting and occupant visual acuity conditions set forth in S5.5.2. You suggested that S5.5.1 requires only the operating instructions, and not the emergency exit designation, to be located within 6 inches of the release mechanism. Similarly, you suggested that the legibility requirements applicable to emergency exit 'markings' per S5.5.2 refer only to the emergency exit designation, and not to the operating instructions for that emergency exit. We disagree with your suggested interpretation. I have recently discussed NHTSA's official interpretation of these provisions in Standard No. 217 in a January 26, 1990 letter to Mr. John G. Sims. A copy of that letter is enclosed for your information. Please contact David Greenburg of this office at (202) 366-2992 if you have any further questions or would like some additional information concerning this subject. Sincerely, Stephen P. Wood Acting Chief Counsel Enclosure"; |
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ID: aiam4994OpenMr. Bill Willett 1609A Sumner Drive Mobile, AL 36605; Mr. Bill Willett 1609A Sumner Drive Mobile AL 36605; Dear Mr. Willett: This responds to your letter of April 17, 1992, wit repect to motor vehicle lighting. You believe that a 'flickering brake light is an improvement to the existing dim-bright red light now used.' The light you have in mind is one which 'flashes on and off at a faster rate than that of the turn signal and emergency flashers.' The light is intended 'to alert the driver that the brakes are applied as long as the brakes are used . . . .' You have asked 'Is there any Federal law preventing me from doing research by adding another device to the vehicle lights.' Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices, and Associated Equipment, requires that stop lamps be steady-burning when the brakes are applied. The National Traffic and Motor Vehicle Safety Act prohibits a 'manufacturer, distributor, dealer, or motor vehicle repair business' from any modification that renders wholly or partially inoperative motor vehicle equipment, such as stop lamps, installed pursuant to a standard such as Standard No. 108. Were the existing stop lamps to be rewired to flash, we would regard the change from steady burning to flashing as rendering the stop lamps partially inoperative within the meaning of this prohibition. However, please note that the prohibition includes only four categories of persons, and does not apply to modifications made by a 'survey group member' who is not within one of those categories. Nor does it apply to modifications made by a vehicle owner. In addition, you should check with the authorities in Alabama to ensure that your modifications do not violate any provision of the State motor vehicle code. Sincerely, Paul Jackson Rice Chief Counsel; |
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ID: aiam2422OpenColonel Dennis Eisnach, South Dakota Highway Patrol, 118 West Capital, Pierre, SD 57501; Colonel Dennis Eisnach South Dakota Highway Patrol 118 West Capital Pierre SD 57501; Dear Colonel Eisnach: This is in response to your telephone conversation with Hugh Oates o this office regarding the possibility of obtaining an exemption for police vehicles from the suspension requirements of Standard No. 215, *Exterior Protection*.; You desire to have vehicles delivered from the manufacturer wit suspensions that raise the vehicle bumper height above the levels required by Standard No. 215 because of the heavy gear you carry in your vehicles.; The National Highway Traffic Safety Administration (NHTSA) issued a advance notice of proposed rulemaking November 9, 1973, (38 FR 31017) concerning the applicability of Part 571, Federal Motor Vehicle Safety Standards, to vehicles designed for use by law-enforcement agencies. This notice specifically mentioned the feasibility of exempting police vehicles from the requirements of Standard No. 208 and Standard No. 215 and sought comments from the public.; After serious consideration of the issues involved, the NHTSA withdre the subject rulemaking on July 9, 1974, (39 FR 25240). That notice stated the NHTSA had determined that rulemaking action to exempt all police vehicles from the requirements of the standards would be inadvisable. a copy of both the advance notice and the withdrawal notice are enclosed for your information. These notices should explain to you the rationale behind the NHTSA's final determination concerning this subject.; In further response to your inquiry, the NHTSA is not authorized t grant an individual exemption from Federal safety standards for vehicles manufactured specifically for the South Dakota Highway Patrol.; Sincerely, Frank A. Berndt, Acting Chief Counsel |
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ID: aiam0220OpenMr. D.J. Broom, Technical Manager (C.V), The Society of Motor Manufacturers and Traders Limited, Forbed House Halkin Street, London SW1, England; Mr. D.J. Broom Technical Manager (C.V) The Society of Motor Manufacturers and Traders Limited Forbed House Halkin Street London SW1 England; Dear Mr. Broom: Thank you for your letter of February 2, 1970, to the Federal Highwa 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 manua supercede the 1965/66 data book as referenced in Section S3 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 S3, lists the Tyre and Wheel Engineering Data Book dates 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 Standard 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 outlines in the October 5, 1968, *Federal Register*.; Sincerely, Rodolfo A. Diaz, Acting Associate Director, Motor Vehicl Programs; |
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.