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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

Displaying 4091 - 4100 of 16517

Interpretations	Date

ID: aiam2662 Open Mr. Malcolm B. Mathieson, Engineering Manager, Thomas Built Buses, Inc. 1408 Courtesy Road, P.O. Box 2450, High Point, NC 27261; Mr. Malcolm B. Mathieson Engineering Manager Thomas Built Buses Inc. 1408 Courtesy Road P.O. Box 2450 High Point NC 27261; Dear Mr. Mathieson: This responds to your August 25, 1977, letter asking several question about the applicability of Standard No. 217, Bus Window Retention and Release, to buses other than school buses.; You first state your conclusion that paragraph S5.2 of the standar applies only to buses other than school buses. Your interpretation of S5.2 is correct. Secondly, you state that S5.2.1 applies to all buses with GVWR's of more than 10,000 pounds. This assertion is incorrect. See S5.2.3. Paragraph S5.2.1 applies only to buses other than school buses that have GVWR's greater than 10,000 pounds.; Your final inquiry pertaining to Standard No. 217 concerns th requirement for unobstructed emergency exits in both school and non-school buses. You first correctly state that paragraphs S5.4 through S5.4.2.1 describe the required size of the unobstructed openings for school buses. You then claim that there is no equivalent description for the size of unobstructed openings required in buses other than school buses. This last statement is not entirely accurate. The amount of unobstructed emergency exit openings required for buses other than school buses is detailed in S5.2. This section establishes requirements for the total area of unobstructed emergency exit openings and for the location of those exits. This section also specifies the extent to which the area of each exit is to be counted in determining compliance with the total unobstructed opening requirement. Therefore, although the standard does not specify minimum size requirements for individual exits in buses other than school buses, the standard does contain other requirements for unobstructed openings in buses other than school buses.; You concluded in your letter that buses other than school buses are no required to use the parallelepiped device in determining whether their rear exits comply with the requirements. This conclusion is accurate. For purposes of clarity, however, you should note that Standard No. 217 does not mandate rear doors in buses other than school buses. Those buses can utilize either rear exits or roof exits. Further, regardless of the fact that you use a rear emergency door in buses other than school buses, you must insure that you also provide the other mandatory exits and the correct area of unobstructed openings as described in paragraphs S5.2 through S5.2.2.; Sincerely, Joseph J. Levin, Jr., Chief Counsel
ID: aiam3970 Open Houston N. Tuel, Jr., Esq., Coder & Tuel, Suite 172, 8801 Folsom Boulevard, Sacramento, CA 95826; Houston N. Tuel Jr. Esq. Coder & Tuel Suite 172 8801 Folsom Boulevard Sacramento CA 95826; Dear Mr. Tuel: This responds to your letter of February 4, 1985, inquiring about th applicability of 49 CFR Part 566, Manufacturer Identification, and 49 CFR Part 573, Defect and Noncompliance Reports, to your client, Stockton Dodge. I regret the delay in our response.; You asked whether Stockton Dodge, as a vehicle alterer, would b considered a manufacturer under the statutory definition of 'manufacturer' in the National Traffic and Motor Vehicle Safety Act as amended, 15 U.S.C. 1391, et seq. (the Act). Based on the information given, the answer is yes.; You state that Stockton Dodge purchases previously certified Dodge van from Chrysler Corporation and converts them into school buses which are intended to be sold directly to school districts. The modifications made by your client include adding seats, strengthening the roof structure, and adding required warning lights and emergency equipment. You state that Stockton Dodge will certify the altered vehicles according to the requirements of 49 CFR Part 567.7, as complying with all Federal motor vehicle safety standards applicable to school buses.; Stockton Dodge sent a letter to the Administrator, dated March 7, 1985 stating that, beginning February 15, 1985, its school bus division would become a final-stage manufacturer. Stockton Dodge stated that they would purchase Dodge B350 vans from Chrysler Corporation which school bus options and would add equipment to alter these vehicles to Type 2 school buses, weighing under 10,000 GVWR. Under our regulations, your client is not considered a final-stage manufacturer because the definition of final-stage manufacturer in 49 CFR Part 568 applies to a person who finishes an incomplete vehicle.; This agency considers Stockton Dodge an alterer of previously certifie motor vehicles, as indicated in your letter, who must comply with the certification requirements of 49 CFR 567.7. Your client's alterations change the vehicle type from a multipurpose van to a school bus and affect components necessary for compliance with safety standards. For these reasons, Stockton Dodge is a manufacturer within the meaning of the Act, as stated above. Stockton Dodge's letter dated March 7, 1985, contains the information required to be submitted under 49 CFR Part 566, Manufacturer Identification. The agency will consider this letter as the manufacturer identification for Stockton Dodge as an alterer.; This agency has also determined that an alterer is considered manufacturer for the purposes of notification and recall for defects or noncompliance under the Act and is subject to the requirements of 49 CFR Part 573, Defect and Noncompliance Reports.; Please note that, under paragraph S4.1 of Standard No. 115, Vehicl Identification Number--Basic Requirements (VIN), Stockton Dodge, as the alterer, should use the VIN assigned by Chrysler Corporation, the original manufacturer of the vehicles.; If you have any further questions, please let me know. Sincerely, Jeffrey R. Miller, Chief Counsel
ID: aiam2398 Open Mr. Byron A. Crampton, Manager of Engineering Services, Truck Body and Equipment Association, Inc., 5530 Wisconsin Avenue, Suite 1220, Washington, DC 20015; Mr. Byron A. Crampton Manager of Engineering Services Truck Body and Equipment Association Inc. 5530 Wisconsin Avenue Suite 1220 Washington DC 20015; Dear Mr. Crampton: This is in response to your letter of August 24, 1976, in which you as whether emergency exits required by a State beyond those required by Standard No. 217, Bus Window Retention and Release, are subject to the performance requirements outlined in S4(b) of Standard No. 220, School Bus Rollover Protection.; Standard No. 220 requires that all emergency exits provided i accordance with Standard No. 217 must meet certain minimum performance levels during and after the simulated rollover test. Additional emergency exits mandated by State law are not exits provided in accordance with Standard No. 217' and, therefore, would not be subject to the requirements os S4(b) of Standard No. 220.; You should note that Standard No. 217, in addition to mandating th provision of certain school bus doors and exits under S5.2, also regulates certain aspects of all emergency exits under other provisions of the regulation.; Sincerely, Frank A. Berndt, Acting Chief Counsel
ID: aiam2232 Open Mr. Lawrence MacEachern, Cal Light Co., 50 Oak Court, Walnut Creek, CA, 94596; Mr. Lawrence MacEachern Cal Light Co. 50 Oak Court Walnut Creek CA 94596; Dear Mr. MacEachern: In your latest letter, dated February 17, 1976, you asked 'Does th Federal motor vehicle safety standards allow the use of one half of an automobile headlight system on a motorcycle?'; There is no Federal prohibition against an owner modifying hi motorcycle to use any lighting configuration, though there may be State or municipal restrictions. The answer where a manufacturer is involved, however, depends upon the type of automobile headlamp system used. Motor Vehicle Safety Standard No. 108 requires a motorcycle to be equipped with a headlamp system conforming to SAE Standard J584, Motorcycle and Motor Driven Cycle Headlamps, April 1964. Two options allowed are use of a single 7 inch sealed beam unit, or of one 5 3/4 inch Type 1 and one 5 3/4 inch Type 2 sealed beam unit, provided these headlamps meet the requirements of SAE J579a, Sealed Beam Headlamp Units for Motor Vehicles, August 1965. Thus, 'one half' of a two-headlamp, or of a four-lamp circular lens passenger car headlighting system could be used on a motorcycle. But use of a system comprised of one Type 1A plus Type 2A (rectangular lens), is not currently permitted under Standard No. 108.; Since there is an equivalence of performance between rectangular an circular lens headlamp systems, if you wish to merchandise a two-lamp (Type 1A plus Type 2A) rectangular system for use on motorcycles, you may wish to submit an additional petition for an amendment of Standard No. 108.; Yours truly, Richard B. Dyson, Assistant Chief Counsel
ID: aiam3073 Open Mr. James Tydings, Specifications Engineer, Thomas Built Buses, Inc., 1408 Courtesy Road, P.O. Box 2450, High Point, NC 27261; Mr. James Tydings Specifications Engineer Thomas Built Buses Inc. 1408 Courtesy Road P.O. Box 2450 High Point NC 27261; Dear Mr. Tydings: This responds to your July 20, 1979, letter asking a questio concerning Standard No. 217, Bus Window Retention. You ask whether paragraph S5.4.2.1(a) permits the parallelepiped device to compress the seat cushion when it is inserted in a school bus emergency exit in accordance with the test procedures of the standard. The answer to your question is no.; Paragraph S5.4.2.1(a) states that each rear emergency exit must provid 'an opening large enough to permit unobstructed passage of a rectangular parallelepiped device...' If the parallelepiped device compresses the seat cushion while being inserted in the bus, its passage is not unobstructed as required by the standard. Accordingly, the National Highway Traffic Safety Administration concludes that the device must enter the vehicle without compressing the seat cushion.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam3589 Open Mr. James Tydings, Specifications Engineer, Thomas Built Buses Inc., 1408 Courtesy Road, P. O. Box 2450, High Point, NC 27261; Mr. James Tydings Specifications Engineer Thomas Built Buses Inc. 1408 Courtesy Road P. O. Box 2450 High Point NC 27261; Dear Mr. Tydings: This responds to your June 28, 1982, letter asking several question about the remanufacture of school buses using old chassis and new bodies.; In general, the use of a new body on an old chassis does not constitut the manufacture of a new motor vehicle. Accordingly, your responsibility as the individual making this modification would simply be to make sure that you do not render inoperative the compliance of the pre- existing vehicle with any of the safety standards with which it complied when it was manufactured and with which it complies at the time of your modifications, i.e., the new body (and the chassis) would have to comply with the same standards with which the old body complied (15 U.S.C. 1397).; In your first hypothetical, you would use a pre-April 1, 1977 chassis In this case the body that you would use would not have to comply with the school bus safety standards that became effective on that date. Seat spacing could be determined by the customer.; Secondly, you would use a post-April 1, 1977 chassis. In this case th vehicle would be required to continue to comply with those standards applicable to it at the time of its manufacture, which includes the school bus safety standards. Seat spacing would be limited in accordance with Standard No. 222.; Your third and fourth hypotheticals are the same as the two noted abov except that the buses involved are not school buses. Once again, the general rule prevails that the buses need not comply with new motor vehicle safety standards, but simply must not have their previous compliance with standards rendered inoperative by you.; Finally, as you indicated in your letter, you should transfer th certification label from the old vehicle to the modified vehicle if you are replacing the vehicle's body.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam3423 Open Mr. Terry Coleman, Codes and Safety Manager, Airstream, Jackson Center, OH 45334; Mr. Terry Coleman Codes and Safety Manager Airstream Jackson Center OH 45334; Dear Mr. Coleman: This responds to your March 26, 1981, letter asking for a clarificatio of the certification requirements applicable to vehicles that you manufacture. The units frequently are completed by you, but in some instances, they are shipped to a final manufacturer for completion of the interior work.; Your first question asks whether you should label the vehicle as final-stage manufacturer since your vehicle is road worthy and needs only the addition of an interior finish prior to sale. In order to certify the vehicle as a final-stage manufacturer, the vehicle that you produce must be a completed vehicle (49 CFR Part 568). A completed vehicle is one that is finished and requires no further manufacturing operations to perform its intended functions with the exceptions of minor finishing operations or readily attachable components. If your vehicle is completed in a manner that it can perform its intended functions, you may label the vehicle as a final-stage manufacturer. The person performing alterations on your vehicle may then be required to add an alterer's label.; If the finishing operation that will be made to your vehicle is mor than the attachment of readily attachable components or minor finish work, the person doing the finishing work may label the vehicle as a final-stage manufacturer. In determining whether the installation of a bathroom, kitchen, furniture, beds, appliances, or seats is an installation of readily attachable components, you should consider whether it requires special expertise or tools. If it requires either, it is not the installation of readily attachable components.; Your second question asks whether your vehicle would be considered chassis-cab in those instances where another manufacturer might be attaching a final-stage label. The answer to this question is no. The definition of chassis-cab in part 567, Certification, states that it is a vehicle with a completed occupant compartment that needs only the addition of work performing or load carrying components to complete its function. It appears that your vehicle does not have a completed occupant compartment and, therefore, would not be considered a chassis-cab.; Finally, you ask what will happen if you label the vehicle as final-stage manufacturer and a subsequent manufacturer significantly alters the vehicle. You ask whether you could treat the vehicle as an incomplete vehicle and furnish the documentation required by Part 568. If you label the vehicle as a final-stage vehicle, you cannot treat it as an incomplete vehicle. However, you may convey information similar to that conveyed in an incomplete vehicle document to the subsequent manufacturer to ensure that it can comply with all of the standards. In fact, that manufacturer may require such information in order to be able to make the necessary modifications.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam4309 Open Mr. Nobuyoshi Takechi, Technical Manager, MMC Services, Inc., 3000 Town Center Suite 1960, Southfield, MI 48075; Mr. Nobuyoshi Takechi Technical Manager MMC Services Inc. 3000 Town Center Suite 1960 Southfield MI 48075; Dear Mr. Takechi: This responds to your letter requesting an interpretation of Standar No. 101, Controls and Displays. Your questions are responded to below.; By way of background information, the National Highway Traffic Safet Administration does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its motor vehicles or equipment comply with applicable safety standards. The following represents our opinion based on the facts provided in your letter.; Your first question concerns the identification requirements for master lighting switch. You stated your belief that if the headlamps and tail lamps are controlled by the master lighting switch, the switch is not required to be marked with any symbol other than that specified in Standard No. 101 for the master lighting switch. You also stated your belief that the manufacturer has an option to use other symbols in addition to that symbol. As discussed below, your understanding is correct.; Section S5.2.1(a) states: >>>Except as specified in S5.2.1(b), any hand- operated control liste in column 1 of Table 1 that has a symbol designated for it in column 3 of that table shall be identified by either the symbol designated column 3 (or symbol substantially similar in form to that shown in column 3) or the word or abbreviation shown in column 2 of that table.... Words or symbols in addition to the required symbol, word or abbreviation may be used at the manufacturer's discretion for the purpose of clarity....<<<; Column 3 of Table 1 designates the symbol shown in your letter for th master light switch. Also, footnote 2 of the Table states that separate identification is not required for headlamps and tail lamps if they are controlled by a master lighting switch. Thus, the master lighting switch symbol is sufficient identification under Standard No. 101 for the control identified in your letter.; A drawing provided with your letter shows various positions of th master lighting switch identified by a word or symbols, which are provided in addition to the master lighting switch symbol. As indicated in the above-quoted text, section S5.2.1(a) permits words or symbols in addition to the required symbol or word, for purposes of clarity.; Your second question concerns identification requirements for an uppe beam control. You stated that you believe no symbol is required for the upper beam control if it is on the turn signal lever, and that it is at the manufacturer's option to use a symbol.; Standard No. 101 does not specify any identification requirements fo an upper beam control, regardless of whether it is on the turn signal lever. Thus, the manufacturer has the option of deciding whether to identify the control and, if so, how to identify it. We note that the symbol you plan to use for future models is the same as designated in Standard No. 101 for the highbeam (upper beam) telltale. Thus, your planned approach appears desirable in minimizing the number of symbol's drivers must familiarize themselves with for the same function.; Sincerely, Erika Z. Jones, Chief Counsel
ID: aiam3136 Open Mr. Hisakazu Murakami, Technical Representative - Safety, Engineering Office of North America, Nissan Motor Co., Ltd., 1919 Pennsylvania Ave., N.W., Suite 707, P.O. Box 57105, Washington, DC 20037; Mr. Hisakazu Murakami Technical Representative - Safety Engineering Office of North America Nissan Motor Co. Ltd. 1919 Pennsylvania Ave. N.W. Suite 707 P.O. Box 57105 Washington DC 20037; Dear Mr. Murakami:#This is in response to your letter of September 14 1979, in which you asked about the applicability of the variable intensity illumination requirements of Federal Motor Vehicle Safety Standard 101-80, Controls and Displays, to various components in your company's automobiles. You listed and identified these parts in Figure 1 of your letter which I will refer to in answering your questions.#The variable intensity illumination requirements of section 5.3.3 of Safety Standard 101-80 are applicable to (1) 'controls, gauges, and their identification,' and to (2) 'any illumination that is provided in the passenger compartment when and only when the headlights are activated.' As noted in section 5 of Safety Standard 101-80, the location, identification, and illumination requirements are applicable only to passenger cars and other vehicles equipped with any control listed in section 5.1 or in column 1 of Table 1. The term 'gauge' is defined in Section 4 as a 'display that is listed in section 5.1 or in Table 2 and is not a telltale.'#Applying these criteria to the list of automobile components in your letter, I have concluded that none of the listed components, except the ordinary clock and the automatic gear position illumination lamp, are subject to the requirements of Section 5.3.3 of Safety Standard 101-80. Since this result resolves the issues raised in Questions Q2.1 - Q2.5 of your letter, I have not addressed them in this response.#The components identified in your diagram by letters a - h (the room lamp, spot lamp, luggage room lamp, personal lamp, radio, foot lamp, step lamp, and the luggage room lamp for hatchback vehicles) are not subject to the requirements of section 5.3.3. This is because they are not controls listed in section 5.1 or in column 1 of Table 1 of Safety Standard 101-80 and because they do not illuminate the passenger compartment when and only when the headlights are activated. Similarly the glove box lamp and the console box lamp (items i and j) are not subject to section 5.3.3. They are not controls listed in Safety Standard 101-80 and they are not activated when and only when the headlights are activated since their activation requires both opening the box lids and switching on the headlights.#The ignition key illumination lamp (item k), which is not a control listed in Safety Standard 101-80, is activated when the light control switch is turned to the 'small lights only' position (this activates the clearance clamps (sic), identification lamps, and other exterior lamps other than the headlights.) When the switch is turned to the position that activates both, the small lights and the headlights, the key illumination lamp is deactivated. Consequently, the lamp is not activated when and only when the headlights are activated and is, therefore, not subject to the variable intensity illumination requirements.#You noted in conversation with Ms. Debra Weiner of my office that your company uses two types of clocks (item 1 in your letter) in its automobiles. One is an ordinary clock whose face is illuminated when and only when the headlights are activated. The requirements of section 5.3.5 would apply to the illumination of this type of clock.#The other clock used in your company's automobiles is a digital clock with a flourescent (sic) readout which shines with greater intensity during the day and with a lower intensity at night when the headlights are activated. Since this clock is not a control or a display listed in Safety Standard 101-80 and its illumination is not activated when and only when the headlamps are activated, the requirements of section 5.3.3 for continuously variable illumination are not applicable. Section 5.3.3 also provides that light intensity for informational readout systems shall have at least two values. The term 'informational readout systems' which is not defined in Safety Standard 101-80 refers to the term 'informational readout display,' which is defined as 'a display using light-emitting diodes, liquid crystals, or other electro illuminating devices where one or more than one type of information or message may be displayed.' The term 'display' includes only those displays listed in section 5.1 or in column 1 of Table 2 of the standard and these listings do not include a digital clock. Therefore, the digital clock would not be subject to the light intensity requirements for informational readout systems.#The automatic gear position illumination lamp (item m in your letter) is subject to the variable intensity illumination requirements of section 5.3.3. Although it is not a control (see preamble to Safety Standard 101-80, 43 FR 27541, June 26, 1978) this lamp is activated when and only when the headlights are activated.#In Question 2 of your letter, you asked for the definition of the terms 'continuously variable' and 'variable.' The term 'continuously variable' is defined in section 5.3.3(a) and (b) of Safety Standard 101-80. It is followed by a description of the two light intensities which must be provided for informational readout systems. The term 'variable' appears in the next sentence in section 5.3.3 which states that:#>>>'The intensity of any illumination that is provided in the passenger compartment when and only when the headlights are activated shall also be variable in a manner that complies with this paragraph. (sic)<<<#The underlined words in the quoted sentence refer to the definition of 'continuously variable' except in the case of informational readout displays where the words refer to illumination of two intensities.#If you have any further questions, I will be happy to answer them.#Sincerely, Frank Berndt, Chief Counsel;
ID: aiam4759 Open Mr. Jack E. Eanes Chief, Vehicle Services State of Delaware Department of Public Safety Division of Motor Vehicles P. O. Box 698 Dover, Delaware, 19903; Mr. Jack E. Eanes Chief Vehicle Services State of Delaware Department of Public Safety Division of Motor Vehicles P. O. Box 698 Dover Delaware 19903; "Dear Mr. Eanes: This is in response to your letter asking whether ver darkly tinted rear windows that obscure the center highmounted stop lamp (CHMSL) required in passenger cars manufactured on or after September 1, 1985 would violate any Federal laws or regulations. Let me begin by apologizing for the delay in this response. I am pleased to have this opportunity to explain our laws and regulations for you. The National Traffic and Motor Vehicle Safety Act (the Safety Act) authorizes this agency to issue safety standards applicable to new motor vehicles and new items of motor vehicle equipment. We have exercised this authority to issue two safety standards that are relevant to your question. The first of these is Standard No. 108, Lamps, Reflective Devices, and Associated Equipment (49 CFR 571.108), which applies to all new vehicles and new replacement equipment for motor vehicles. Among the requirements set forth in this Standard is a requirement for all passenger cars manufactured on or after September 1, 1985 to be equipped with a CHMSL of specified minimum size, brightness, and visibility from the range of locations set forth in the standard. The second relevant standard is Standard No. 205, Glazing Materials (49 CFR 571.205). This standard applies to all new vehicles and all new glazing for use in motor vehicles, and includes specifications for minimum levels of light transmittance of the glazing (70 percent light transmittance in areas requisite for driving visibility, which includes all windows in passenger cars). Section 108(a)(1)(A) of the Safety Act (15 U.S.C. 1397(a)(1)(A)) provides that no person may manufacture or sell any vehicle unless it is in conformity with all applicable safety standards. A new passenger car with a rear window tinted so darkly that the CHMSL was not easily visible would probably not be in conformity with Standards No. 108 and 205, and so could not legally be manufactured or sold in the United States. However, this prohibition on the manufacture or sale of a nonconforming vehicle does not apply after a vehicle is first sold to a consumer. Both before and after the first sale of a vehicle, section 108(a)(2) of the Safety Act (15 U.S.C. 1397(a)(2)) provides that: 'No manufacturer, distributor, dealer, or motor vehicle repair business shall knowingly render inoperative, in whole or in part, any device or element of design installed on a motor vehicle or item of motor vehicle equipment in compliance with an applicable Federal motor vehicle safety standard . . .' If any of the listed commercial entities were to install tint film or otherwise darken the rear windows on passenger cars so that the light transmittance of that window plus the darkening material was below 70 percent, those entities would be 'rendering inoperative' the light transmittance of the rear window of the car, in violation of Federal law. This same prohibition in Federal law makes it unlawful for a service station to permanently remove the safety belts or permanently disconnect the brake lines on a car. Please note that the Safety Act does not apply to the actions of individual vehicle owners. Vehicle owners may alter their own vehicles and operate them on the highways as they please, even if the vehicle no longer complies with the safety standards after such alterations. Hence, no provision of the Safety Act or our safety standards makes it unlawful for vehicle owners themselves to tint or otherwise darken the rear window of their car so that its light transmittance is below 70 percent and/or its CHMSL is obscured. The individual States, however, do have authority to regulate the modifications that vehicle owners may make to their own vehicles. The States also have the authority to establish requirements for vehicles to be registered or operated in that State. You indicated in your letter that the State of Delaware 'allows vehicle rear windows to be tinted as dark as the owner desires.' While I am not familiar with Delaware law, I assume that this statute, and similar statutes adopted by other States, does not purport to legitimize conduct -- the rendering inoperative of glazing and CHMSLs by firms installing window tinting -- that is illegal under Federal law. In other words, any commercial firms installing window tinting that results in light transmittance of less than 70 percent and/or reduces the required brightness of the CHMSL would have violated the 'render inoperative' provision in Federal law, even if Delaware permits individual owners to make such modifications themselves and to register and operate vehicles with rear windows and CHMSLs that would not comply with the requirements of the Federal safety standards for new vehicles. Conversely, the Federal law setting requirements for the manufacture and sale of new vehicles and limiting the modifications commercial enterprises can make to those vehicles does not prohibit the State of Delaware from establishing lesser limits on owner modifications to their own vehicles and as the minimum requirements for vehicles to be operated and registered in the State of Delaware. Thus, there does not appear to be any legal conflict between Federal law and Delaware law, and Delaware would be free to enforce the provisions of its law. We would, however, urge the State of Delaware to carefully consider the adverse safety consequences that will result from the provision of its law. NHTSA has determined that a 70 percent light transmittance minimum for new vehicles is the appropriate level to assure motor vehicle safety, and that the CHMSL on passenger cars enhances motor vehicle safety. It is not clear why the State of Delaware would conclude that the safety need that justifies requiring not less than 70 percent light transmittance and CHMSLs in new passenger cars is satisfied by allowing far lower light transmittance levels and lower-brightness CHMSLs in passenger cars to be operated in the State. I hope that this information is helpful. If you have any further questions or need additional information about this topic, please feel free to contact Dorothy Nakama of my staff at this address or by telephone at (202) 366-2992. Sincerely, Paul Jackson Rice 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.

Interpretations	Date

ID: aiam2662 Open Mr. Malcolm B. Mathieson, Engineering Manager, Thomas Built Buses, Inc. 1408 Courtesy Road, P.O. Box 2450, High Point, NC 27261; Mr. Malcolm B. Mathieson Engineering Manager Thomas Built Buses Inc. 1408 Courtesy Road P.O. Box 2450 High Point NC 27261; Dear Mr. Mathieson: This responds to your August 25, 1977, letter asking several question about the applicability of Standard No. 217, Bus Window Retention and Release, to buses other than school buses.; You first state your conclusion that paragraph S5.2 of the standar applies only to buses other than school buses. Your interpretation of S5.2 is correct. Secondly, you state that S5.2.1 applies to all buses with GVWR's of more than 10,000 pounds. This assertion is incorrect. See S5.2.3. Paragraph S5.2.1 applies only to buses other than school buses that have GVWR's greater than 10,000 pounds.; Your final inquiry pertaining to Standard No. 217 concerns th requirement for unobstructed emergency exits in both school and non-school buses. You first correctly state that paragraphs S5.4 through S5.4.2.1 describe the required size of the unobstructed openings for school buses. You then claim that there is no equivalent description for the size of unobstructed openings required in buses other than school buses. This last statement is not entirely accurate. The amount of unobstructed emergency exit openings required for buses other than school buses is detailed in S5.2. This section establishes requirements for the total area of unobstructed emergency exit openings and for the location of those exits. This section also specifies the extent to which the area of each exit is to be counted in determining compliance with the total unobstructed opening requirement. Therefore, although the standard does not specify minimum size requirements for individual exits in buses other than school buses, the standard does contain other requirements for unobstructed openings in buses other than school buses.; You concluded in your letter that buses other than school buses are no required to use the parallelepiped device in determining whether their rear exits comply with the requirements. This conclusion is accurate. For purposes of clarity, however, you should note that Standard No. 217 does not mandate rear doors in buses other than school buses. Those buses can utilize either rear exits or roof exits. Further, regardless of the fact that you use a rear emergency door in buses other than school buses, you must insure that you also provide the other mandatory exits and the correct area of unobstructed openings as described in paragraphs S5.2 through S5.2.2.; Sincerely, Joseph J. Levin, Jr., Chief Counsel
ID: aiam3970 Open Houston N. Tuel, Jr., Esq., Coder & Tuel, Suite 172, 8801 Folsom Boulevard, Sacramento, CA 95826; Houston N. Tuel Jr. Esq. Coder & Tuel Suite 172 8801 Folsom Boulevard Sacramento CA 95826; Dear Mr. Tuel: This responds to your letter of February 4, 1985, inquiring about th applicability of 49 CFR Part 566, Manufacturer Identification, and 49 CFR Part 573, Defect and Noncompliance Reports, to your client, Stockton Dodge. I regret the delay in our response.; You asked whether Stockton Dodge, as a vehicle alterer, would b considered a manufacturer under the statutory definition of 'manufacturer' in the National Traffic and Motor Vehicle Safety Act as amended, 15 U.S.C. 1391, et seq. (the Act). Based on the information given, the answer is yes.; You state that Stockton Dodge purchases previously certified Dodge van from Chrysler Corporation and converts them into school buses which are intended to be sold directly to school districts. The modifications made by your client include adding seats, strengthening the roof structure, and adding required warning lights and emergency equipment. You state that Stockton Dodge will certify the altered vehicles according to the requirements of 49 CFR Part 567.7, as complying with all Federal motor vehicle safety standards applicable to school buses.; Stockton Dodge sent a letter to the Administrator, dated March 7, 1985 stating that, beginning February 15, 1985, its school bus division would become a final-stage manufacturer. Stockton Dodge stated that they would purchase Dodge B350 vans from Chrysler Corporation which school bus options and would add equipment to alter these vehicles to Type 2 school buses, weighing under 10,000 GVWR. Under our regulations, your client is not considered a final-stage manufacturer because the definition of final-stage manufacturer in 49 CFR Part 568 applies to a person who finishes an incomplete vehicle.; This agency considers Stockton Dodge an alterer of previously certifie motor vehicles, as indicated in your letter, who must comply with the certification requirements of 49 CFR 567.7. Your client's alterations change the vehicle type from a multipurpose van to a school bus and affect components necessary for compliance with safety standards. For these reasons, Stockton Dodge is a manufacturer within the meaning of the Act, as stated above. Stockton Dodge's letter dated March 7, 1985, contains the information required to be submitted under 49 CFR Part 566, Manufacturer Identification. The agency will consider this letter as the manufacturer identification for Stockton Dodge as an alterer.; This agency has also determined that an alterer is considered manufacturer for the purposes of notification and recall for defects or noncompliance under the Act and is subject to the requirements of 49 CFR Part 573, Defect and Noncompliance Reports.; Please note that, under paragraph S4.1 of Standard No. 115, Vehicl Identification Number--Basic Requirements (VIN), Stockton Dodge, as the alterer, should use the VIN assigned by Chrysler Corporation, the original manufacturer of the vehicles.; If you have any further questions, please let me know. Sincerely, Jeffrey R. Miller, Chief Counsel
ID: aiam2398 Open Mr. Byron A. Crampton, Manager of Engineering Services, Truck Body and Equipment Association, Inc., 5530 Wisconsin Avenue, Suite 1220, Washington, DC 20015; Mr. Byron A. Crampton Manager of Engineering Services Truck Body and Equipment Association Inc. 5530 Wisconsin Avenue Suite 1220 Washington DC 20015; Dear Mr. Crampton: This is in response to your letter of August 24, 1976, in which you as whether emergency exits required by a State beyond those required by Standard No. 217, Bus Window Retention and Release, are subject to the performance requirements outlined in S4(b) of Standard No. 220, School Bus Rollover Protection.; Standard No. 220 requires that all emergency exits provided i accordance with Standard No. 217 must meet certain minimum performance levels during and after the simulated rollover test. Additional emergency exits mandated by State law are not exits provided in accordance with Standard No. 217' and, therefore, would not be subject to the requirements os S4(b) of Standard No. 220.; You should note that Standard No. 217, in addition to mandating th provision of certain school bus doors and exits under S5.2, also regulates certain aspects of all emergency exits under other provisions of the regulation.; Sincerely, Frank A. Berndt, Acting Chief Counsel
ID: aiam2232 Open Mr. Lawrence MacEachern, Cal Light Co., 50 Oak Court, Walnut Creek, CA, 94596; Mr. Lawrence MacEachern Cal Light Co. 50 Oak Court Walnut Creek CA 94596; Dear Mr. MacEachern: In your latest letter, dated February 17, 1976, you asked 'Does th Federal motor vehicle safety standards allow the use of one half of an automobile headlight system on a motorcycle?'; There is no Federal prohibition against an owner modifying hi motorcycle to use any lighting configuration, though there may be State or municipal restrictions. The answer where a manufacturer is involved, however, depends upon the type of automobile headlamp system used. Motor Vehicle Safety Standard No. 108 requires a motorcycle to be equipped with a headlamp system conforming to SAE Standard J584, Motorcycle and Motor Driven Cycle Headlamps, April 1964. Two options allowed are use of a single 7 inch sealed beam unit, or of one 5 3/4 inch Type 1 and one 5 3/4 inch Type 2 sealed beam unit, provided these headlamps meet the requirements of SAE J579a, Sealed Beam Headlamp Units for Motor Vehicles, August 1965. Thus, 'one half' of a two-headlamp, or of a four-lamp circular lens passenger car headlighting system could be used on a motorcycle. But use of a system comprised of one Type 1A plus Type 2A (rectangular lens), is not currently permitted under Standard No. 108.; Since there is an equivalence of performance between rectangular an circular lens headlamp systems, if you wish to merchandise a two-lamp (Type 1A plus Type 2A) rectangular system for use on motorcycles, you may wish to submit an additional petition for an amendment of Standard No. 108.; Yours truly, Richard B. Dyson, Assistant Chief Counsel
ID: aiam3073 Open Mr. James Tydings, Specifications Engineer, Thomas Built Buses, Inc., 1408 Courtesy Road, P.O. Box 2450, High Point, NC 27261; Mr. James Tydings Specifications Engineer Thomas Built Buses Inc. 1408 Courtesy Road P.O. Box 2450 High Point NC 27261; Dear Mr. Tydings: This responds to your July 20, 1979, letter asking a questio concerning Standard No. 217, Bus Window Retention. You ask whether paragraph S5.4.2.1(a) permits the parallelepiped device to compress the seat cushion when it is inserted in a school bus emergency exit in accordance with the test procedures of the standard. The answer to your question is no.; Paragraph S5.4.2.1(a) states that each rear emergency exit must provid 'an opening large enough to permit unobstructed passage of a rectangular parallelepiped device...' If the parallelepiped device compresses the seat cushion while being inserted in the bus, its passage is not unobstructed as required by the standard. Accordingly, the National Highway Traffic Safety Administration concludes that the device must enter the vehicle without compressing the seat cushion.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam3589 Open Mr. James Tydings, Specifications Engineer, Thomas Built Buses Inc., 1408 Courtesy Road, P. O. Box 2450, High Point, NC 27261; Mr. James Tydings Specifications Engineer Thomas Built Buses Inc. 1408 Courtesy Road P. O. Box 2450 High Point NC 27261; Dear Mr. Tydings: This responds to your June 28, 1982, letter asking several question about the remanufacture of school buses using old chassis and new bodies.; In general, the use of a new body on an old chassis does not constitut the manufacture of a new motor vehicle. Accordingly, your responsibility as the individual making this modification would simply be to make sure that you do not render inoperative the compliance of the pre- existing vehicle with any of the safety standards with which it complied when it was manufactured and with which it complies at the time of your modifications, i.e., the new body (and the chassis) would have to comply with the same standards with which the old body complied (15 U.S.C. 1397).; In your first hypothetical, you would use a pre-April 1, 1977 chassis In this case the body that you would use would not have to comply with the school bus safety standards that became effective on that date. Seat spacing could be determined by the customer.; Secondly, you would use a post-April 1, 1977 chassis. In this case th vehicle would be required to continue to comply with those standards applicable to it at the time of its manufacture, which includes the school bus safety standards. Seat spacing would be limited in accordance with Standard No. 222.; Your third and fourth hypotheticals are the same as the two noted abov except that the buses involved are not school buses. Once again, the general rule prevails that the buses need not comply with new motor vehicle safety standards, but simply must not have their previous compliance with standards rendered inoperative by you.; Finally, as you indicated in your letter, you should transfer th certification label from the old vehicle to the modified vehicle if you are replacing the vehicle's body.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam3423 Open Mr. Terry Coleman, Codes and Safety Manager, Airstream, Jackson Center, OH 45334; Mr. Terry Coleman Codes and Safety Manager Airstream Jackson Center OH 45334; Dear Mr. Coleman: This responds to your March 26, 1981, letter asking for a clarificatio of the certification requirements applicable to vehicles that you manufacture. The units frequently are completed by you, but in some instances, they are shipped to a final manufacturer for completion of the interior work.; Your first question asks whether you should label the vehicle as final-stage manufacturer since your vehicle is road worthy and needs only the addition of an interior finish prior to sale. In order to certify the vehicle as a final-stage manufacturer, the vehicle that you produce must be a completed vehicle (49 CFR Part 568). A completed vehicle is one that is finished and requires no further manufacturing operations to perform its intended functions with the exceptions of minor finishing operations or readily attachable components. If your vehicle is completed in a manner that it can perform its intended functions, you may label the vehicle as a final-stage manufacturer. The person performing alterations on your vehicle may then be required to add an alterer's label.; If the finishing operation that will be made to your vehicle is mor than the attachment of readily attachable components or minor finish work, the person doing the finishing work may label the vehicle as a final-stage manufacturer. In determining whether the installation of a bathroom, kitchen, furniture, beds, appliances, or seats is an installation of readily attachable components, you should consider whether it requires special expertise or tools. If it requires either, it is not the installation of readily attachable components.; Your second question asks whether your vehicle would be considered chassis-cab in those instances where another manufacturer might be attaching a final-stage label. The answer to this question is no. The definition of chassis-cab in part 567, Certification, states that it is a vehicle with a completed occupant compartment that needs only the addition of work performing or load carrying components to complete its function. It appears that your vehicle does not have a completed occupant compartment and, therefore, would not be considered a chassis-cab.; Finally, you ask what will happen if you label the vehicle as final-stage manufacturer and a subsequent manufacturer significantly alters the vehicle. You ask whether you could treat the vehicle as an incomplete vehicle and furnish the documentation required by Part 568. If you label the vehicle as a final-stage vehicle, you cannot treat it as an incomplete vehicle. However, you may convey information similar to that conveyed in an incomplete vehicle document to the subsequent manufacturer to ensure that it can comply with all of the standards. In fact, that manufacturer may require such information in order to be able to make the necessary modifications.; Sincerely, Frank Berndt, Chief Counsel
ID: aiam4309 Open Mr. Nobuyoshi Takechi, Technical Manager, MMC Services, Inc., 3000 Town Center Suite 1960, Southfield, MI 48075; Mr. Nobuyoshi Takechi Technical Manager MMC Services Inc. 3000 Town Center Suite 1960 Southfield MI 48075; Dear Mr. Takechi: This responds to your letter requesting an interpretation of Standar No. 101, Controls and Displays. Your questions are responded to below.; By way of background information, the National Highway Traffic Safet Administration does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its motor vehicles or equipment comply with applicable safety standards. The following represents our opinion based on the facts provided in your letter.; Your first question concerns the identification requirements for master lighting switch. You stated your belief that if the headlamps and tail lamps are controlled by the master lighting switch, the switch is not required to be marked with any symbol other than that specified in Standard No. 101 for the master lighting switch. You also stated your belief that the manufacturer has an option to use other symbols in addition to that symbol. As discussed below, your understanding is correct.; Section S5.2.1(a) states: >>>Except as specified in S5.2.1(b), any hand- operated control liste in column 1 of Table 1 that has a symbol designated for it in column 3 of that table shall be identified by either the symbol designated column 3 (or symbol substantially similar in form to that shown in column 3) or the word or abbreviation shown in column 2 of that table.... Words or symbols in addition to the required symbol, word or abbreviation may be used at the manufacturer's discretion for the purpose of clarity....<<<; Column 3 of Table 1 designates the symbol shown in your letter for th master light switch. Also, footnote 2 of the Table states that separate identification is not required for headlamps and tail lamps if they are controlled by a master lighting switch. Thus, the master lighting switch symbol is sufficient identification under Standard No. 101 for the control identified in your letter.; A drawing provided with your letter shows various positions of th master lighting switch identified by a word or symbols, which are provided in addition to the master lighting switch symbol. As indicated in the above-quoted text, section S5.2.1(a) permits words or symbols in addition to the required symbol or word, for purposes of clarity.; Your second question concerns identification requirements for an uppe beam control. You stated that you believe no symbol is required for the upper beam control if it is on the turn signal lever, and that it is at the manufacturer's option to use a symbol.; Standard No. 101 does not specify any identification requirements fo an upper beam control, regardless of whether it is on the turn signal lever. Thus, the manufacturer has the option of deciding whether to identify the control and, if so, how to identify it. We note that the symbol you plan to use for future models is the same as designated in Standard No. 101 for the highbeam (upper beam) telltale. Thus, your planned approach appears desirable in minimizing the number of symbol's drivers must familiarize themselves with for the same function.; Sincerely, Erika Z. Jones, Chief Counsel
ID: aiam3136 Open Mr. Hisakazu Murakami, Technical Representative - Safety, Engineering Office of North America, Nissan Motor Co., Ltd., 1919 Pennsylvania Ave., N.W., Suite 707, P.O. Box 57105, Washington, DC 20037; Mr. Hisakazu Murakami Technical Representative - Safety Engineering Office of North America Nissan Motor Co. Ltd. 1919 Pennsylvania Ave. N.W. Suite 707 P.O. Box 57105 Washington DC 20037; Dear Mr. Murakami:#This is in response to your letter of September 14 1979, in which you asked about the applicability of the variable intensity illumination requirements of Federal Motor Vehicle Safety Standard 101-80, Controls and Displays, to various components in your company's automobiles. You listed and identified these parts in Figure 1 of your letter which I will refer to in answering your questions.#The variable intensity illumination requirements of section 5.3.3 of Safety Standard 101-80 are applicable to (1) 'controls, gauges, and their identification,' and to (2) 'any illumination that is provided in the passenger compartment when and only when the headlights are activated.' As noted in section 5 of Safety Standard 101-80, the location, identification, and illumination requirements are applicable only to passenger cars and other vehicles equipped with any control listed in section 5.1 or in column 1 of Table 1. The term 'gauge' is defined in Section 4 as a 'display that is listed in section 5.1 or in Table 2 and is not a telltale.'#Applying these criteria to the list of automobile components in your letter, I have concluded that none of the listed components, except the ordinary clock and the automatic gear position illumination lamp, are subject to the requirements of Section 5.3.3 of Safety Standard 101-80. Since this result resolves the issues raised in Questions Q2.1 - Q2.5 of your letter, I have not addressed them in this response.#The components identified in your diagram by letters a - h (the room lamp, spot lamp, luggage room lamp, personal lamp, radio, foot lamp, step lamp, and the luggage room lamp for hatchback vehicles) are not subject to the requirements of section 5.3.3. This is because they are not controls listed in section 5.1 or in column 1 of Table 1 of Safety Standard 101-80 and because they do not illuminate the passenger compartment when and only when the headlights are activated. Similarly the glove box lamp and the console box lamp (items i and j) are not subject to section 5.3.3. They are not controls listed in Safety Standard 101-80 and they are not activated when and only when the headlights are activated since their activation requires both opening the box lids and switching on the headlights.#The ignition key illumination lamp (item k), which is not a control listed in Safety Standard 101-80, is activated when the light control switch is turned to the 'small lights only' position (this activates the clearance clamps (sic), identification lamps, and other exterior lamps other than the headlights.) When the switch is turned to the position that activates both, the small lights and the headlights, the key illumination lamp is deactivated. Consequently, the lamp is not activated when and only when the headlights are activated and is, therefore, not subject to the variable intensity illumination requirements.#You noted in conversation with Ms. Debra Weiner of my office that your company uses two types of clocks (item 1 in your letter) in its automobiles. One is an ordinary clock whose face is illuminated when and only when the headlights are activated. The requirements of section 5.3.5 would apply to the illumination of this type of clock.#The other clock used in your company's automobiles is a digital clock with a flourescent (sic) readout which shines with greater intensity during the day and with a lower intensity at night when the headlights are activated. Since this clock is not a control or a display listed in Safety Standard 101-80 and its illumination is not activated when and only when the headlamps are activated, the requirements of section 5.3.3 for continuously variable illumination are not applicable. Section 5.3.3 also provides that light intensity for informational readout systems shall have at least two values. The term 'informational readout systems' which is not defined in Safety Standard 101-80 refers to the term 'informational readout display,' which is defined as 'a display using light-emitting diodes, liquid crystals, or other electro illuminating devices where one or more than one type of information or message may be displayed.' The term 'display' includes only those displays listed in section 5.1 or in column 1 of Table 2 of the standard and these listings do not include a digital clock. Therefore, the digital clock would not be subject to the light intensity requirements for informational readout systems.#The automatic gear position illumination lamp (item m in your letter) is subject to the variable intensity illumination requirements of section 5.3.3. Although it is not a control (see preamble to Safety Standard 101-80, 43 FR 27541, June 26, 1978) this lamp is activated when and only when the headlights are activated.#In Question 2 of your letter, you asked for the definition of the terms 'continuously variable' and 'variable.' The term 'continuously variable' is defined in section 5.3.3(a) and (b) of Safety Standard 101-80. It is followed by a description of the two light intensities which must be provided for informational readout systems. The term 'variable' appears in the next sentence in section 5.3.3 which states that:#>>>'The intensity of any illumination that is provided in the passenger compartment when and only when the headlights are activated shall also be variable in a manner that complies with this paragraph. (sic)<<<#The underlined words in the quoted sentence refer to the definition of 'continuously variable' except in the case of informational readout displays where the words refer to illumination of two intensities.#If you have any further questions, I will be happy to answer them.#Sincerely, Frank Berndt, Chief Counsel;
ID: aiam4759 Open Mr. Jack E. Eanes Chief, Vehicle Services State of Delaware Department of Public Safety Division of Motor Vehicles P. O. Box 698 Dover, Delaware, 19903; Mr. Jack E. Eanes Chief Vehicle Services State of Delaware Department of Public Safety Division of Motor Vehicles P. O. Box 698 Dover Delaware 19903; "Dear Mr. Eanes: This is in response to your letter asking whether ver darkly tinted rear windows that obscure the center highmounted stop lamp (CHMSL) required in passenger cars manufactured on or after September 1, 1985 would violate any Federal laws or regulations. Let me begin by apologizing for the delay in this response. I am pleased to have this opportunity to explain our laws and regulations for you. The National Traffic and Motor Vehicle Safety Act (the Safety Act) authorizes this agency to issue safety standards applicable to new motor vehicles and new items of motor vehicle equipment. We have exercised this authority to issue two safety standards that are relevant to your question. The first of these is Standard No. 108, Lamps, Reflective Devices, and Associated Equipment (49 CFR 571.108), which applies to all new vehicles and new replacement equipment for motor vehicles. Among the requirements set forth in this Standard is a requirement for all passenger cars manufactured on or after September 1, 1985 to be equipped with a CHMSL of specified minimum size, brightness, and visibility from the range of locations set forth in the standard. The second relevant standard is Standard No. 205, Glazing Materials (49 CFR 571.205). This standard applies to all new vehicles and all new glazing for use in motor vehicles, and includes specifications for minimum levels of light transmittance of the glazing (70 percent light transmittance in areas requisite for driving visibility, which includes all windows in passenger cars). Section 108(a)(1)(A) of the Safety Act (15 U.S.C. 1397(a)(1)(A)) provides that no person may manufacture or sell any vehicle unless it is in conformity with all applicable safety standards. A new passenger car with a rear window tinted so darkly that the CHMSL was not easily visible would probably not be in conformity with Standards No. 108 and 205, and so could not legally be manufactured or sold in the United States. However, this prohibition on the manufacture or sale of a nonconforming vehicle does not apply after a vehicle is first sold to a consumer. Both before and after the first sale of a vehicle, section 108(a)(2) of the Safety Act (15 U.S.C. 1397(a)(2)) provides that: 'No manufacturer, distributor, dealer, or motor vehicle repair business shall knowingly render inoperative, in whole or in part, any device or element of design installed on a motor vehicle or item of motor vehicle equipment in compliance with an applicable Federal motor vehicle safety standard . . .' If any of the listed commercial entities were to install tint film or otherwise darken the rear windows on passenger cars so that the light transmittance of that window plus the darkening material was below 70 percent, those entities would be 'rendering inoperative' the light transmittance of the rear window of the car, in violation of Federal law. This same prohibition in Federal law makes it unlawful for a service station to permanently remove the safety belts or permanently disconnect the brake lines on a car. Please note that the Safety Act does not apply to the actions of individual vehicle owners. Vehicle owners may alter their own vehicles and operate them on the highways as they please, even if the vehicle no longer complies with the safety standards after such alterations. Hence, no provision of the Safety Act or our safety standards makes it unlawful for vehicle owners themselves to tint or otherwise darken the rear window of their car so that its light transmittance is below 70 percent and/or its CHMSL is obscured. The individual States, however, do have authority to regulate the modifications that vehicle owners may make to their own vehicles. The States also have the authority to establish requirements for vehicles to be registered or operated in that State. You indicated in your letter that the State of Delaware 'allows vehicle rear windows to be tinted as dark as the owner desires.' While I am not familiar with Delaware law, I assume that this statute, and similar statutes adopted by other States, does not purport to legitimize conduct -- the rendering inoperative of glazing and CHMSLs by firms installing window tinting -- that is illegal under Federal law. In other words, any commercial firms installing window tinting that results in light transmittance of less than 70 percent and/or reduces the required brightness of the CHMSL would have violated the 'render inoperative' provision in Federal law, even if Delaware permits individual owners to make such modifications themselves and to register and operate vehicles with rear windows and CHMSLs that would not comply with the requirements of the Federal safety standards for new vehicles. Conversely, the Federal law setting requirements for the manufacture and sale of new vehicles and limiting the modifications commercial enterprises can make to those vehicles does not prohibit the State of Delaware from establishing lesser limits on owner modifications to their own vehicles and as the minimum requirements for vehicles to be operated and registered in the State of Delaware. Thus, there does not appear to be any legal conflict between Federal law and Delaware law, and Delaware would be free to enforce the provisions of its law. We would, however, urge the State of Delaware to carefully consider the adverse safety consequences that will result from the provision of its law. NHTSA has determined that a 70 percent light transmittance minimum for new vehicles is the appropriate level to assure motor vehicle safety, and that the CHMSL on passenger cars enhances motor vehicle safety. It is not clear why the State of Delaware would conclude that the safety need that justifies requiring not less than 70 percent light transmittance and CHMSLs in new passenger cars is satisfied by allowing far lower light transmittance levels and lower-brightness CHMSLs in passenger cars to be operated in the State. I hope that this information is helpful. If you have any further questions or need additional information about this topic, please feel free to contact Dorothy Nakama of my staff at this address or by telephone at (202) 366-2992. Sincerely, Paul Jackson Rice Chief Counsel";

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