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: nht72-2.16OpenDATE: 05/19/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Norman W. Quinn, Esq. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of May 5 on behalf of your client Lee Ross. Mr. Ross has developed a motor vehicle deceleration warning system that, as described by you, activates two amber lights on the rear of a vehicle. Your letter indicate that these lamps would be incorporated into a vehicle back-up lamp system and that Mr. Ross envisions his system as an aftermarket accessory item rather than as new vehicle original equipment. You state your understanding that Motor Vehicle Safety Standard No. 108 would not preclude marketing the system as an aftermarket accessory, and that back-up lamps are required to be white in color. You ask our advice whether Standard No. 108 prohibits amber lamps in the back-up lighting system and, if so, whether a proposal for amendment of the Standard to allow the system would be feasible. Standard No. 108 would in certain instances preclude the aftermarket sale of an amber deceleration warning system incorporated into a back-up lamp system. Standard No. 108 as of January 1, 1972, does cover certain aftermarket equipment items, and in some instances would preclude the sale of a back-up light system with amber lamps. Lighting equipment manufactured on or after that date as replacement for similar equipment on vehicles manufactured on or after January 1, 1972, must meet Standard No. 108 which, as you have noted, requires that the color of the back-up lamps be white. Federal law would not preclude sale of this system for use on motor vehicles manufactured before January 1, 1972, or purchase of an amber system by the owner of a vehicle manufactured after that date if he wished to change over from a white to amber system. As a practical matter, however, I believe That virtually every State has a requirement that back-up lamps be white, and that a back-up light with amber bulbs or lenses would be forbidden. Standard No. 108 would not preclude sale of the Ross System as a separate lighting device. I do not know what position the States would take on such a matter. Our research contracts on deceleration warning system indicate that further development and testing under field conditions is necessary before specific proposals can be made by NHTSA. Therefore, I do not think action on a proposal by Mr. Ross would be feasible at this time, though we would welcome his comments to our Docket 69-19 as a comment to be considered in future rulemaking on this subject. |
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ID: nht72-2.17OpenDATE: 11/21/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: American Plywood Association TITLE: FMVSS INTERPRETATION TEXT: This is in response to your letter of October 25, 1972, in which you ask whether there are any NHTSA requirements applicable to "do-it-yourself" plans for camper trailers. Certain Federal requirements are applicable to the camper trailers which will be built based on your plans. These are Federal Motor Vehicle Safety Standard No. 108. "Lamps, Reflective Devices, and Associated Equipment" (49 CFR 571.108). Requirements which we expect to issue in the near future will apply to the tires with which such trailers are equipped (proposed Standards Nos. 119 and 120). Moreover, manufacturers of these trailers are required by NHTSA "certification" regulations (49 CFR Part 567) to certify the trailer's confermity with the motor vehicle safety standards. These requirements apply to the finished trailer itself, and not to the plans for it, but the plans should include stops that will cause the finished trailer to conferm to all applicable requirements. I have enclosed directions on how you may obtain copies of NHTSA requirements. |
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ID: nht72-2.18OpenDATE: 10/03/72 FROM: AUTHOR UNAVAILABLE; C. A. Baker for E. T. Driver; NHTSA TO: Schlen Body and Equipment Co. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of September 22 to Mr. Ed Leysath of this Office regarding Interpretations of FMVSS No. 108 on required mounting of marker lights on your dump trailers. In answer to your first problem, a combination front clearance and side marker lamp must meet the requirements for both; therefore, the full 180-degree visibility is required. If you determine that it is not practicable to mount the combination lamp in your alternate location, because of a greater possibility of damage, then separate lamps should be considered. In answer to your second problem, because of the configuration and end use of your dump semi-trailers, your interpretation that rear clearance lamps mounted in a light box just below the rear trailer crossmember are as high as practicable is correct. |
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ID: nht72-2.19OpenDATE: 08/11/72 FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA TO: Imperial Fire Apparatus TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of July 21 to Mr. (Illegible Words) Truck Body and Equipment Association, Inc., concerning interpretations of FMVSS No. 108 requirements relating to fire trucks. The answers to the questions you asked are as follows: I. Flashing Identification, Clearance, and (Illegible Word) Lights. (Illegible Word) calls for all identification clearance, and (Illegible Words) to be wired into a motor driven (Illegible Word) with a selector switch for "steady on" or "flashing". Is this procedure allowable? (Illegible Word). Flashing side (Illegible Words), but not clearance and identification lamps, are permitted by FMVSS No. 108. II. Flashing Lights. Customer calls for a second set of identification and clearance lamps ((Illegible Words) and power) to be mounted adjacent to the existing lighting. This second set of lights is to be wired into a motor driven flasher with a separate control switch located in the cab. Is this procedure allowable? Yes. The additional or supplemental lamps are permitted by FMVSS No. 108, and flashing these additional lamps is (Illegible Word) in non-compliance with the standard. Regulations of individual states may, however, be applicable to this arrangement. III. Battery Disconnect Switch. On many trucks, the battery is wired into a master switch whereby the battery can be completely isolated from the electrical system. When this switch is in the "off" position, all light switches including identification, clearance, and four (4) way hazard flashers become in-operative. With the vehicle's engine shut down, the four (4) way hazard signals may only be activated by turning (Illegible Word) to "on" and turning four (4) way hazard switch to "on". Is this installation in compliance with SAE (Illegible Words) 4.21. If there are lights that must be activated by a single driver action, could you please note them. This installation is in compliance with the requirements of FMVSS No. 108, providing the master switch is separate from the ignition switch and the hazard warning signal lamps will flash with the master switch on and the ignition switch off. |
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ID: nht72-2.2OpenDATE: 02/23/72 FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA TO: Cosco Household Products, Inc. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of January 12, 1972, concerning Motor Vehicle Safety Standard No. 213, "Child Seating Systems." You ask specific questions, enclosing 3 diagrams, regarding the application of certain provisions of the standard to a child seat you wish to build. You state that this seat in its present form is composed of a tubular steel frame, and has a molded plastic shell to seat the child, to provide head restraint, and to assist in containing the child under lateral decelerations. You ask whether the shell is a rigid component, stating that it will most probably be manufactured of polyethylene of about .100 inch thickness, and will be deformable by hand. We believe that such a shell could be considered a non-rigid component. There is not at present a definition of "rigid" in the standard and manufacturers should rely on generally available definitions of the term in determining whether or not components are rigid. You state further that in those areas where the shell contacts the tubular frame it is unquestionably rigid, and ask whether energy-absorbing material could be applied between the frame and the shell, rather than between the shell and the child as specified in S4.10 of the standard. In the particular case you present, it is not clear whether the rigidity of the shell is inherent or results because of its attachment to the frame. If by cushioning this attachment the rigidity will be eliminated, we would no longer consider the component to be rigid. However, the amount of cushioning needed would depend upon the amount necessary to eliminate the rigidity, and would not necessarily be the 1/2-inch thickness specified in S4.10 for covering rigid components. This determination would be for the manufacturer to make, based upon his analysis of when the rigidity has been removed from the component. With reference to the question presented on sketch 1, we believe it is answered in the preceding paragraphs. Concerning sketch 2 you ask what the standard requires at point N, where there is "essentially no energy-absorbing material between the bottom of the groove and the rigid tube." S4.10 of the standard requires rigid components that may contact the head or torso, with certain exceptions, to be "covered" with energy-absorbing material having a thickness of at least 1/2 inch. If the point N with which you are concerned can contact the head or torso of the child during impact, taking into account compression of the material adjacent to it, then it must be covered with at least the specified thickness of energy-absorbing material. Your third sketch asks whether energy-absorbing material is required where the shell loops over the tubular steel frame, when the side of the shell is greater than 24 square inches. You are apparently assuming that the area in question is contactable as that term is used in S4.10. In our view the answer to this question depends upon whether the part of the seat in question is actually a "side" and if so if its rigidity is uniform. If the area in question creates a frontal projection we would not consider it to be a "side" under S4.10. If it does not, but the side is significantly more rigid in the area of the tubular frame, then we would not consider the exemption in S4.10.3 to apply, since the shell would not be one component. The hazard created would be identical if the tubular frame were exposed, and not covered by the shell. Finally, you ask for any information on the status of Notice 5, published September 23, 1970 (35 F.R. 14786). A final rule based on this notice is in preparation, and we expect that it will be issued in the near future. At the same time, we have placed in the docket a report entitled "Report of Test on Child Vehicles and Their Energy Absorbing Materials." This report summarizes recent test work done to investigate test procedures for head restraints and energy absorbing materials for child seats. |
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ID: nht72-2.20OpenDATE: 10/02/72 FROM: AUTHOR UNAVAILABLE; C. A. Baker for E. T. Driver; NHTSA TO: The Grote Manufacturing Company TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of September 25 to Mr. Lewis C. Owen of this Office concerning the mounting of front clearance lamps on trucks and buses over 80 inches in width. You are correct in your interpretation that these lamps must be mounted to indicate the overall width of the vehicle and as near the top as practicable. The width and height of the body in relation to that of the cab on a van type truck governs the proper location; therefore, each application must be judged individually. However, you are correct that the proper location should be the top front corners of the body when the height of the body is significantly higher than the cab. Since this name question has been directed to us repeatedly and some manufacturers are installing cab mounted lights and others body mounted lights on quite similar vehicles, we anticipate that this aspect will be addressed in future rulemaking actions. |
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ID: nht72-2.21OpenDATE: 01/17/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: Truck Body and Equipment Association, Inc. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of December 21, 1971, to Lawrence R. Schneider requesting an interpretation on the mounting of front identification lamps. Standard No. 108 requires that identification lamps be mounted "as close as practicable to the top of the vehicle" (Table II). The "vehicle" is the vehicle as completed, and not the incomplete vehicle. Therefore, if the "top" of the vehicle, i.e., the highest point, is a location other than the cab, the identification lamps must be mounted at the "top", and not on the cab, if it is practicable to do so. Generally, manufacturers of van-body vehicles have found it practicable to mount identification lamps on the van body. Modified lighting diagram 0-1 which you enclosed originally depicted the correct location of identification lamps for a truck with a van body. If the manufacturer of the cab portion of a truck has placed identification lamps on the cab, the lamps need not be removed when the lamps necessary for conformance are added at the "top." Sincerely, December 21, 1971 Mr. Lawrence R. Schneider, Chief Counsel NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION U. S. Department of Transportation Subject: REQUEST FOR INTERPRETATION ON MOUNTING HEIGHT OF FRONT IDENTIFICATION LAMPS. Re: Lamps, Reflective Devices, and Associated Equipment Federal Motor Vehicle Safety Standard No. 108 The above referenced FMVSS No. 108, becoming effective January 1, 1972, establishes the location and mounting heights of the front identification lamps by stating----- " . . . as close as practicable to the top of the vehicle . . ." "On the front only-- and No part of the lamps or mountings shall extend below the top of the vehicle's windshield." Insofar as trailers are concerned, identification lamps are not required on the front of the trailer. The reasoning for this is that the identification lamps stop the truck tractor will serve the requirement. We shall use a typical van body truck as an example. (See attached Lighting Diagram O-1.) It is our contention that if identification lamps are mounted on top of chassis-cab vehicles--i.e. incomplete vehicles--as supplied by the chassis manufacturers, it is permissible to leave these lamps in place. We contend that it is not necessary to remove these chassis supplied lamps, nor is it necessary to add an additional set of identification lamps at the top of the body. Of course we realize that if there are not any identification lamps on top of the cab (vehicles 80 or more inches overall width), we would be held responsible to equip the truck with front identification lamps (as close as practicable to the top of the vehicle) as required by FMVSS No. 108. Please advise us in writing if our interpretations are correct and in full compliance with FMVSS No. 108. Your earliest response will be appreciated. Very truly yours, TRUCK BODY AND EQUIPMENT ASSOCIATION -- Paul A. Tatarski Manager Engineering Services Enclosure: (Graphics omitted) FOR VEHICLES OF 80 OR MORE INCHES OVERALL WIDTH RECOMMENDED LAMP AND REFLECTOR LOCATIONS IN ACCORDANCE WITH THE FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108 (DRAWING IS NOT TO SCALE) The general areas indicated for lamps and reflectors are acceptable to the U.S. Department of Transportations National Highway Traffic Safety Administration and the Bureau of Motor Carrier Safety. Consult Federal MVSS No. 108 and the applicable tables therein for exact requirements such as: mounting height limitations lamp combinations and alternative locations. LEGEND 1. Headlamps (2)-white (4 optional) 2. Front side-marker lamps (2)-amber 3. Front side reflectors (2)-amber 4. Front turn-signal lamps (2)-amber 4a. Front turn-signal lamps (2)-amber (optional location) 5. Front identification lamps (3)-amber 5a. Front identification lamps (3)-amber (optional location) 6. Front clearance lamps (2)-amber 7. Rear side-marker lamps (2)-amber 8. Rear side reflectors (2)-red 9. Rear identification lamps (3)-red 10. Rear clearance lamps (2)-red 11. Rear reflectors (2)-red 12. Rear stop-tail & turn-signal lamps (2)-red 13. Rear licence plate lamp (1)-white 14. Rear backup lamp (1)-white (location optional provided optical requirements are met) 15. Intermediate side-marker lamps (2)-amber (if vehicle is 30' or more overall length) 16. Intermediate side reflectors (2)-amber (if vehicle is 30' or more overall length) NOTE LAMPS AND REFLECTORS MAY BE MOUNTED AT OTHER PRACTICABLE LOCATIONS PROVIDED LOCATION AND VISIBILITY REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108 ARE MET. Lighting Diagram Supplement 1/1/71 |
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ID: nht72-2.22OpenDATE: 02/18/72 FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA TO: FMC Corporation TITLE: FMVSS INTERPRETATION TEXT: This is in reply to the questions you ask in your letter of January 7 concerning the Federal Motor Vehicle Safety Standards. In your first question you ask whether a vehicular hazard warning signal operating unit must conform to SAE Recommended Practice J910 specified in Table 1 of Standard No. 106, or to the newer SAE J910s. The answer is J910; the revision J910a cannot become a requirement of Standard No. 103 without ruleasking action by this agency. As of (Illegible Words) has issued no proposal that (Illegible Word) be adopted. You also ask whether hazard lamps at both ends of the vehicle must flash simultaneously. The operating unit is defined in (Illegible Word) as a device "which causes all turn signal lamps to flash simultaneously . . ." This means that all turn signal lamps must flash on the same cycle, and that separate cycles for froat and rear turn signal lamps are not permissible. In answer to your second question, Standard No. 108 does not yet specify requirements for side turn signal lamps, and thus does not prohibit their use on your motor home. As indicated in our "Program Plan for Motor Vehicle Safety Standards," October 1971, this agency intends to issue a notice in the near future proposing to incorporate requirements for side turn signal lamps in Standard No. 108 Finally you ask whether Standard No. 101 requires illumination (Illegible Words) handlamp switch with park ponition to operate clearance, I.D., and the marker lamps. Standard No. 101 does not require illumination of the headlamp switch, even if the switch does (Illegible Word) is the operation of other lamps whose controls, if separate, would have to be illuminated. |
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ID: nht72-2.23OpenDATE: 09/13/72 FROM: AUTHOR UNAVAILABLE; E. T. Driver for R. L. Carter; NHTSA TO: Hon. P. H. D. Fratinghuysen - H.O.R. TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of August 31, 1972, to Secretary of Transportation John A. Volpe, concerning Mr. Richard J. Orgass' comments on headlighting for motor vehicles. The National Traffic and Motor Vehicle Safety Act of 1966 required that the initial Federal motor vehicle safety standards be based on existing standards. In this respect, Federal Motor Vehicle Safety Standard No. 108, the initial Federal standard on lighting requirements, specifies that headlamps conform to existing standards, these of the Society of Automotive Engineers (SAE Standards J579a and J5SCa) for sealed beam headlamps. The SAE standards were developed by authorities in the field of vehicular lighting and were adopted by a number of State and Federal regulatory agencies prior to the existance of Standard No. 108. Specifying the use of these standard headlamp assemblies enhances traffic safety, since replacement assemblies are readily available when needed by the vehicle operator. It is recognized that a number of currently available headlamps produce higher lighting intensities than those permitted by Standard No. 108. Such headlamps, while providing a more effectively illuminated roadway for the driver behind the lamps, could under certain traffic environments produce an annoying or even blinding effect on approaching drivers. Therefore, all aspects of highway safety must be considered during the development of new or revised requirements which will eventually be included in Standard No. 108. As an indication of the National Highway Traffic Safety Administration's plans for improving headlighting, I am enclosing a copy of an Advance Notice of Proposed Rule making relating to Standard No. 108. Included In the Notice are several proposals which affect the present requirements for headlamps. Also, a recently completed research program on improved forward lighting included studies and evaluations on the performance and other technical aspects of several types of headlamps, including the quartz-halogen type. Results of this research will assist in the development of requirements for more effective headlighting systems. It is anticipated that a second notice including new and revised requirements for headlighting will be Issued late in 1972. Thank you for bringing Mr. Orgass' comments to my attention. |
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ID: nht72-2.24OpenDATE: 05/09/72 FROM: AUTHOR UNAVAILABLE; D. W. Toms; NHTSA TO: Department of California Highway Patrol TITLE: FMVSS INTERPRETATION TEXT: This is in reply to your letter of April 18, 1972, requesting an interpretation of the requirements of Federal Motor Vehicle Safety Standard No. 108 which relates to the use of mechanical aimers on headlamps. Standard No. 108 references, in Tables I and III, SAE Standard J580a. As stated in your letter, SAE J580a specifies in part that "Headlamps shall be designed so that they may be checked by mechanical aimers without the removal of any ornamental trim rings or other parts." The language in this requirement, and that contained in other referenced and subreferenced SAE standards, does not specifically identify the design or complete dimensional details of "mechanical aimers." Therefore, the use of any mechanical aimer, including those fitted with special adapters for specific vehicles, would be permitted under the above stated requirement. Specifically, you asked, "If a vehicle is so designed that the headlamps cannot be checked with mechanical aimers of the type now commonly available without the removal of ornamental trim rings or other parts, does it meet the requirements of Federal Standard 108?" A "commonly available" aimer is defined as one that is manufactured and offered for sale, including an aimer with adapters for special applications. A vehicle which is so designed that the headlamps cannot be checked with mechanical aimers as thus defined, without the removal of ornamental trim rings or other parts, would not meet the requirements of Standard No. 108. |
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.