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
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ID: aiam4410OpenWilliam J. Maloney, Esq., Rode & Qualey, 295 Madison Avenue, New York, NY 10017; William J. Maloney Esq. Rode & Qualey 295 Madison Avenue New York NY 10017; Dear Mr. Maloney: This responds to your letter seeking an interpretation of Standard No 211, *Wheel Nuts, Wheel Discs, and Hub Caps* (49 CFR S571.211). Section S3 of this standard states, 'Wheel nuts, hub caps, and wheel discs for use on passenger cars and multipurpose passenger vehicles shall not incorporate winged projections.' You asked whether these components are permitted to incorporate winged projections if the winged projections do not extend beyond the wheel rim when mounted. As we have stated several times in the past, winged projects are prohibited on wheel nuts, hub caps, and wheel discs, *regardless* of whether the winged projections are recessed below the level of the wheel rim.; This issue was first raised in response to the notice of propose rulemaking for the initial Federal motor vehicle safety standards, published on December 3, 1966 (31 FR 15212). That notice proposed language for Standard No. 211 that was identical with that which was adopted. In response to this proposal, a manufacture commented that it did not consider its winged wheel nuts a hazard to pedestrians or cyclists, because the winged wheel nuts did not extend beyond the outermost projection of the wheel rim. The final rule published on February 3, 1967 (32 FR 2408) did not make any change to the proposed language in response to this comment.; In a report issued on March 17, 1967 on the development of the initia Federal motor vehicle safety standards, the agency summarized the comments on the proposed standards and its response to those comments. I have enclosed a copy of the summary of Standard No. 211 for your information. As you will see, this summary recited the manufacturer's comments on winged projections that were located inside the outermost projection of the wheel rim and tire. The summary goes on to say, 'The Agency did not agree, and retained the prohibition of even such recess winged structures lest the clothes of child pedestrians and others be caught.' Hence, arguments about the unobjectionability of *recessed* winged projections were considered and rejected by the agency more than twenty years ago.; We have repeated this position in our subsequent interpretations o Standard No. 211. I have enclosed copies of an August 26, 1970 letter to Mr. James S. Campbell ('...any winged projection is prohibited, even if recessed.'), a November 25, 1975 letter to Mr. James J. Schardt ('Our interpretation of Standard No. 211 is that S3 prohibits winged projections that do not extend beyond the outer edge of the tire or rim, as well as those that do.'), and a January 31, 1980 letter to Mr. Doug Smith ('...the standard prohibits the use of all winged projections regardless of the extent to which they extend from a rim.').; After examining the history of this requirement, we have concluded tha the language of the standard itself draws no distinction between winged projections that do not extend beyond the outer edge of the rim and those that do. Instead, section S3 provides that the identified components 'shall *not* incorporate winged projections.' We reaffirm our previous interpretations, which concluded that this language prohibits *all* winged projections on the identified components, not just those that extend beyond the outer edge of the rim.; You concluded by asking me to state that recessed winged projection may by imported, offered for sale, and sold in the United States. I cannot make such a statement. Since those winged projections are prohibited by Standard No. 211, section 108(a)(1)(A) of the National Traffic and Motor Vehicle Safety Act, as amended (15 U.S.C. 1397(a)(1)(A)) makes it illegal to 'manufacture for sale, sell, offer for sale, or introduce or deliver for introduction in interstate commerce, or import into the United States' any wheel discs, wheel nuts, or hub caps that incorporate winged projections. Section 109 of the Safety Act (15 U.S.C. 1398) specifies a civil penalty of up to $1000 for each violation of section 108(a), and we would consider each sale of wheel discs, wheel nuts, or hub caps with winged projections to be a separate violation of section 108(a).; If you have any further questions on this matter, please feel free t contact Mr. Kratzke at this address or by telephone at (202) 366-2992.; Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam1612OpenMr. Mike A. Read,Design Engineer, Spring Division,Borg-Warner Corporation,700 South 25th Avenue,Bellwood, Illinois 60104; Mr. Mike A. Read Design Engineer Spring Division Borg-Warner Corporation 700 South 25th Avenue Bellwood Illinois 60104; Dear Mr. Read:#This is in reply to your letter of September 13, 1974 pointing out discrepancies between our two standards covering motor vehicle hydraulic brake systems, Nos. 105-75 and 122.#We intend to amend Standard No. 122 in the near future to be consistent with Standard No. 105-75.This will clarify that the same interpretation will be given master cylinder reservoir and capacity requirements.#Thank you for pointing this out to us. #Yours truly,Richard B. Dyson,Acting Chief Counsel; |
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ID: aiam0900OpenMr. Robert I. Yeoman, Plaskolite, Inc., P.O. Box 1497, 1770 Joyce Avenue, Columbus, OH 43216; Mr. Robert I. Yeoman Plaskolite Inc. P.O. Box 1497 1770 Joyce Avenue Columbus OH 43216; Dear Mr. Yeoman: This is in reply to your letter of October 16, 1972, requesting a DO number for safety glazing materials. You indicate that your understanding is that such a number is required in order to obtain approval under ANS Z26.1-1966.; Under Federal Standards applicable to motor vehicle glazing material (Motor Vehicle Safety Standard No. 205, 49 CFR 571.205) the manufacturer of the material is responsible for certifying the conformity of the material to the standard. The NHTSA does not provide prior approvals, but tests materials it purchases on the open market. Motor Vehicle Safety Standard 205 incorporates by reference, with some exceptions, ANS Standard Z26.1-1966. The DOT number to which you refer has been an optional method by which prime glazing material manufacturers certify their materials. Beginning April 1, 1973, prime glazing material manufacturers will be required to use the symbol DOT and a code number in certifying their materials. Plaskolite Incorporated is hereby assigned code number 98. The method for certifying is more fully explained in the Standard.; While the NHTSA does not require prior approvals of glazing materials such approvals are required by certain States. You may obtain information regarding these approvals from the American Association of Motor Vehicle Administrators, Suite 500, 1828 L Street, N.W., Washington, D.C. 20036.; Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicl Programs; |
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ID: aiam3785OpenMr. Richard McCarl, American Isuzu Motors Inc., Whittier, CA 90601; Mr. Richard McCarl American Isuzu Motors Inc. Whittier CA 90601; Dear Mr. McCarl: This responds to your November 23, 1983 letter regarding th applicability of motor vehicle certification requirements to a new vehicle to be imported by Isuzu Motors. This small utility vehicle would be certified as a truck. Isuzu dealers will offer for the vehicle an optional rear seat which can be installed by simply bolting it to the vehicle. The basic vehicle already has the necessary mountings for the seat, so the seat installation can apparently be readily accomplished. You have asked whether installation of these seats constitutes 'alteration' of the vehicle by the dealer, requiring the addition of an alterer's label in accordance with 49 CFR 567.7.; Based on your description of the seat installation process, it appear that dealers installing the seats would be subject to 49 CFR 567.6, 'Requirements for persons who do not alter certified vehicles or do so with readily attachable components.' Since the seats appear to be 'readily attachable components,' section 567.6 requires dealers to leave the manufacturer's certification label in place and requires no alterer's label to be added.; If you have further questions on this matter, please contact us. Sincerely, Frank Berndt, Chief Counsel |
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ID: aiam4040OpenMr. David M. Cima, 318 Temko Terrace, Daytona Beach, FL 32018; Mr. David M. Cima 318 Temko Terrace Daytona Beach FL 32018; Dear Mr. Cima: This responds to your letter asking about the identification an visibility requirements applicable to a gear position indicator for an automatic transmission. You asked whether the indicator must be visible to the driver (1) when he or she enters the car or (2)whenever anyone is behind the wheel. As discussed below, the indicator must be visible whenever anyone is in the driver's seating position.; By way of background information, the National Highway Traffic Safet Administration (NHTSA) 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 vehicles or equipment comply with applicable standards. The following represents our opinion based on the facts provided in your letter.; Section S3.2 of Federal Motor Vehicle Safety Standard No. 102 *Transmission Shift Lever Sequence, Starter Interlock, and Transmission Braking Effect*, requires that the '(i)dentification of shift lever position of automatic transmissions and of the shift lever pattern of manual transmission . . .shall be *permanently displayed in view of the driver*.' (Emphasis added) NHTSA has previously interpreted this provision as requiring a display that can be seen regardless of the operating mode of the engine. Thus, it is not permissible for the display to be visible (e.g., in the case of an electronic display, become activated) only after the driver turns on the ignition.; Your letter raises the issue of whether it is permissible for a electronic display to become activated at the time the driver enters the car and, if so, whether it must remain activated indefinitely as long as the driver remains in the car, even if the ignition is not turned on. It is our opinion that it is permissible for an electronic display to become activated at the time the driver enters the car and need not be activated when there is no person in the driver's seating position. Section S3.2's requirement that the identification of shift lever positions of automatic transmissions be 'permanently displayed' is modified by the phrase 'in view of the driver.' It is our opinion that no such display is required at times when no driver is in the car, i.e., no person in the driver's seating position. We also conclude, however that such a display must remain activated indefinitely as long as the driver remains in the driver's seating position even if the ignition is not turned on. If the display only remained activated for a specific period of time, such as five minutes, it would not be 'permanently' displayed.; I hope this information is helpful. Sincerely, Erika Z. Jones, Chief Counsel |
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ID: aiam2897OpenMr. Suminori Eguchi, Chief Engineer, Technical Department, Ichikoh Industries, Ltd, 80 Itado, Isehara City, Kanagawa 259-11, JAPAN; Mr. Suminori Eguchi Chief Engineer Technical Department Ichikoh Industries Ltd 80 Itado Isehara City Kanagawa 259-11 JAPAN; Dear Mr. Eguchi: This is in reply to your letter of September 22, 1978, to Bill Eason o our Office of Rulemaking asking several questions about motor vehicle headlamps and the amendment to Motor Vehicle Safety Standard No. 108 issued on July 27, 1978.; Your questions and our answers are: 1. Ichikoh headlamps are designed to comply with SAE Standard J579 with maximum candela not exceeding 37,500. Does the amendment allow Ichikoh to place 'DOT' and the new designation code on the lens of each headlight?; Ichikoh's practice reflects compliance with the option afforded b S4.1.1.33 until July 27, 1978. The deletion of candlepower permitted by J579c but does not require it. Thus, Ichikoh may continue its existing practice under the amendment. One purpose of the marking code, however, is to enable a consumer to replace original equipment headlamps with lamps of compatible photometric output. Currently, S4.1.1.21 as amended requires the lens of each Ichikoh headlamp designed to conform to J579c to be marked with the new code on and after July 1, 1979. Obviously such a marking will be misleading if, even though designed to conform to J579c, a headlamp's maximum candela does not exceed 37,500. Accordingly, we are reviewing this problem with the idea of proposing rulemaking that would delete the code requirement for all headlamps whose maximum candela does not exceed 37,500. We do not anticipate a change in the requirement of S4.1.1.21 that the lens of each J579c headlamp be marked with the 'DOT' symbol since Ichikoh headlamps comply with J579c, even if they do not take advantage of the now-permissible maximum.; 2. With reference to your quality control system, will the headlamp 'be allowed to exceed 37,500 cd without any modification of the light source (filament) and wattage?'; I am not quite sure what you mean. If you are asking whether Ichiko may relax quality control so that an occasional headlamp may exceed 37,500 cd, the answer is yes. Headlamps designed to J579c are not restricted to the maximum imposed by J579a.; 3. You ask our comments on possible mismatch of headlamps on the sam vehicle, i.e., one low intensity headlamp and one high intensity headlamp.; NHTSA is concerned about this possibility and, as indicated in reply t your first question, is considering rulemaking to delete the code requirement for low intensity J579c headlamps. Your second question, however, does raise the issue of identification of headlamps whose candela may exceed 37,500 but whose maxima are far less than 75,000. We shall also consider this issue and may issue a consumer bulletin advocating replacement of headlamps in pairs to help resolve this potential problem.; 4. You ask whether NHTSA intends to adopt the concept of ECE Regulatio No. 20 in the near future. This Regulation requires a mark on a headlamp lens indicating candlepower grade.; The NHTSA does not plan to adopt the requirements of Regulation No. 2 because this regulation is in essence an indicator of quality control.; I hope this answers your questions. Sincerely, Joseph J. Levin, Jr., Chief Counsel |
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ID: aiam1242OpenMr. David E. Martin, Manager, Automotive Safety Engineering, Environmental Activities Staff, General Motors Technical Center, General Motors Corporation, Warren, MI 48090; Mr. David E. Martin Manager Automotive Safety Engineering Environmental Activities Staff General Motors Technical Center General Motors Corporation Warren MI 48090; Dear Mr. Martin: Dr. Gregory has asked me to reply to your letter of August 28, 1973, i which you request our endorsement of new labels General Motors intends to use to fulfill its responsibilities under part 567 of Title 49 of the Code of Federal Regulations.; The wording on the label meets the requirements of paragraph 567.4(g) The color of the paint under the label 'window' would determine conformity with the contrasting color requirements in paragraph 567.4(f).; It would appear that the material would '. . . be permanently affixed . .' if it '. . . is tightly bonded to the surface of the vehicle panel. . . .' However, it has not been the practice of the National Highway Traffic Safety Administration to endorse label materials.; Thank you for your continuing cooperation. Sincerely, Robert L. Carter |
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ID: aiam5201OpenMs. Lillie Rene Erwin 365089 TDC Mt View Unit H-1 Rt. 4 Box 800 Gatesville, TX 76528-9399; Ms. Lillie Rene Erwin 365089 TDC Mt View Unit H-1 Rt. 4 Box 800 Gatesville TX 76528-9399; Dear Ms. Erwin: This responds to your May 15, 1993, letter to forme Secretary Card. Because your letter concerns motor vehicle safety, it has been referred to the National Highway Traffic Safety Administration (NHTSA) for response. You are concerned with vehicles used by the State of Texas to transport prisoners because these vehicles have metal seats and no occupant restraints for the prisoners and asked who you should contact to voice your complaint. The National Traffic and Motor Vehicle Safety Act authorizes NHTSA to issue motor vehicle safety standards that apply to the manufacture and sale of new motor vehicles and new items of motor vehicle equipment. NHTSA has exercised this authority to establish a standard which requires seat belts to be installed at all designated seating positions in many, but not all, vehicles. In addition, different belt installation requirements apply depending on the vehicle type, seating position within the vehicle, and the GVWR of the vehicle. Accordingly, I cannot identify the specific belt installation requirements for the vehicle in which you were transported without knowing the date of the vehicle's manufacture, the vehicle's seating capacity, and gross vehicle weight rating (GVWR) of the vehicle. In addition, your concerns about the State of Texas' use of the vehicle are not addressed by Federal law, which addresses only the manufacture and sale of motor vehicles, not their subsequent use. Because your questions concern the safety of the State of Texas' vehicles used to transport prisoners, you may wish to contact the Governor's Office, the head of the Texas prison system, or your state representative. I hope you find this information helpful. Sincerely, John Womack Acting Chief Counsel; |
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ID: aiam0003OpenStephen E. Selander, Esq. Legal Staff General Motors Corporation New Center One Building 3031 West Grand Boulevard P.O. Box 33122 Detroit, MI 48232; Stephen E. Selander Esq. Legal Staff General Motors Corporation New Center One Building 3031 West Grand Boulevard P.O. Box 33122 Detroit MI 48232; "Dear Mr. Selander: This responds to your February 17, 1992 request fo interpretations of Federal Motor Vehicle Safety Standards No. 101, Controls and Displays and No. 105, Hydraulic Brake Systems, as those standards would apply to an electric vehicle (GMEV) that General Motors (GM) is preparing to sell in the future. You requested the agency's concurrence with, or guidance regarding, nine proposed interpretations. Your questions are addressed below. Before discussing the substantive issues that you raised, I note that you requested confidential treatment for portions of certain materials that you provided relating to the brake system planned for the electric vehicle. These materials were previously submitted to NHTSA, and the agency granted confidentiality for portions of the materials in letters dated July 18, 1991 and August 12, 1991. In a letter accompanying your request for interpretation, GM released from its request for confidential treatment portions of the materials for which confidentiality had previously been granted. NHTSA's earlier grants of confidentiality remain in effect for the remaining portions for which GM continues to seek confidential treatment. Accordingly, this letter does not cite any of the confidential information. I also note that, in one of the attachments to your letter, you suggested several amendments to Standard No. 105 that you believe would facilitate the introduction of electric vehicles. As you know, NHTSA recently issued an advance notice of proposed rulemaking (ANPRM) to solicit comments to help the agency determine what existing standards may need modification to meet the needs associated with the introduction of electric vehicles and what new standards may have to be written specifically for electric vehicles. See 56 FR 67038, December 27, 1991. We will consider your recommendations concerning Standard No. 105 as we evaluate the comments on the ANPRM. The scope of this letter is limited to addressing how the current requirements of Standards No. 101 and No. 105 would apply to your planned vehicle. By way of background information, NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles and equipment comply with applicable requirements. The following represents our opinion based on the facts provided in your letter. Standard No. 101, Controls and Displays GM Proposed Interpretation 1: Permit electrically powered vehicles to use symbols that are appropriate for indicating electric power reserve. You asked two questions regarding how Standard No. 101 would apply to the GM electric vehicle. The first question concerned the identification for a gauge that would monitor battery charge as a percent of full charge. This gauge would serve as the functional equivalent of a fuel gauge in traditional internal combustion engine (ICE) vehicles. You stated, however that it would be inappropriate and potentially misleading to use Standard No. 101's fuel symbol (a picture of a gasoline pump) for a gauge indicating electric power reserve. You stated that you planned to identify the gauge with the ISO battery symbol (a picture of a battery), which you indicated is substantially similar to that found in Standard No. 101 for electrical charge. You requested NHTSA's concurrence that electric vehicles are permitted to use symbols that are appropriate for identifying electric power reserve and not the Standard No. 101 fuel symbol. Standard No. 101 requires that new vehicles with any display listed in the standard must meet specified requirements for the location, identification and illumination of such display. See S5(a). Thus, the primary issue raised by your question is whether a gauge indicating electric power reserve is among the displays listed in the standard, and if so, what identification requirements apply. As you noted in your letter, one of the displays listed in Standard No. 101 is a fuel gauge. See S5.1 and Table 2. The dictionary defines 'fuel' as combustible matter used to maintain fire, as coal, wood, oil, etc. See Random House Dictionary of the English Language (unabridged edition). Electrical power provided by a battery does not come within the meaning of 'fuel.' Therefore, a gauge indicating electric power reserve for an electric vehicle is not a fuel gauge. Another display listed in Standard No. 101 is an electrical charge gauge. This term refers to gauges that indicate whether, and the extent to which, a vehicle's battery is charging. Therefore, a gauge indicating electric power reserve for an electric vehicle is not an electric charge gauge within the meaning of Standard No. 101. Since a gauge indicating electric power reserve is not otherwise covered by Standard No. 101 or any other standard, its identification is at the option of the manufacturer. GM Proposed Interpretation 2: Allow the 'Service Soon' telltale to indicate loss of powertrain oil pressure for the GMEV. Your second question concerned whether low oil pressure may be indicated by activation of a 'Service Soon' telltale instead of one identified by Standard No. 101's oil pressure symbol (a picture of an oil can) or the word 'oil.' You stated that a 'Service Soon' telltale would be more appropriate for an electric vehicle, since it (unlike ICE vehicles) can continue to be driven without oil pressure. One of the displays listed in Standard No. 101 is an oil pressure telltale. While the seriousness of low oil pressure may be different for electric vehicles than ICE vehicles, the condition for activation of an oil pressure telltale (low oil pressure) would be the same. It is our opinion that Standard No. 101's identification requirements would apply to an oil pressure telltale for an electric vehicle. If a manufacturer is concerned that the oil pressure symbol or the word 'oil' might be misleading to drivers familiar with ICE vehicles, the manufacturer is free to provide additional words or symbols for the purpose of clarity. See S5.2.3. It is not clear, however, that the telltale you plan would be considered a low oil pressure telltale within the meaning of Standard No. 101. You state that, as currently planned, the electric vehicle will be equipped with a 'Service Soon' telltale which will light in the event of a malfunction that could eventually cause damage to the vehicle powertrain, but does not require immediate attention. It thus appears that the telltale might monitor several possible vehicle conditions, one of which is low oil pressure. Standard No. 101 does not require that any of the displays listed in the standard be provided or that two or more displays, if provided, be provided separately. NHTSA has previously concluded that a multipurpose telltale which monitors two functions, oil pressure and coolant temperature, may be identified by the word 'Engine.' See December 29, 1978 letter to Ford Motor Company. The basis for this interpretation was that while Standard No. 101 specifies requirements for oil pressure and coolant temperature telltales, it does not specify any requirements for a single telltale which covers both conditions. For the same reason, if GM provided a single telltale monitoring several vehicle conditions, one of which was low oil pressure, the standard's requirements for an oil pressure telltale would not apply and the identification for that telltale would be at the discretion of the manufacturer. Standard No. 105, Hydraulic Brake Systems You asked seven questions regarding how Standard No. 105 would apply to the GM electric vehicle. You provided the following general description of the brake system planned for the vehicle: The brake system consists of front hydraulic disc (service) brakes, rear electric drum (service and parking) brakes, four-wheel ABS, and regenerative braking. Brake pedal forces and travel are comparable to conventional power assisted hydraulic brake systems, and are independent of the state-of-charge of the vehicle's battery pack. The design features a manual hydraulic 'push through' to apply the front brakes in the event of any electrical failure. Standard No. 105 applies to passenger cars and various other vehicle types with 'hydraulic service brake systems.' See S3. Since the service brakes of the GM electric vehicle would be partly hydraulic brakes and partly electric brakes, a preliminary issue is whether the standard would apply to the vehicle. As discussed below, it is our opinion that the standard would apply to the vehicle. The term 'hydraulic brake system' is defined in S4 as 'a system that uses hydraulic fluid as a medium for transmitting force from a service brake control to the service brake, and that may incorporate a brake power assist unit, or a brake power unit.' The term 'service brake' is defined at Part 571.3 as 'the primary mechanism designed to stop a motor vehicle.' The planned braking system would use hydraulic fluid as a medium for transmitting force from the service brake control to the front brake portion of the service brake. It is our interpretation that this is sufficient, under the definition of 'hydraulic brake system,' for the braking system to be considered a 'hydraulic brake system,' even though hydraulic fluid is not used for the rear brake portion of the service brake. Therefore, Standard No. 105 would apply to the vehicle. GM Proposed Interpretation 3: The GMEV parking brake is mechanically retained in accordance with the requirements of S5.2. Your first question on Standard No. 105 concerned S5.2's requirement that vehicles be manufactured 'with a parking brake system of a friction type with a solely mechanical means to retain engagement.' You stated that the parking brake on the GMEV would be applied and released by electrical means, but would be retained by a mechanical latching device. You requested NHTSA's concurrence that the planned parking brake would satisfy the requirement for mechanically retained engagement. We agree that S5.2 permits the parking brake to be applied and released by electrical or other non-mechanical means, so long as engagement is held by solely mechanical means. Your next several questions concern Standard No. 105's brake failure requirements. As noted by your letter, these requirements are set forth in S5.1.2 (partial failure), S5.1.3 (inoperative brake power assist unit or brake power unit), and S5.5 (failure in antilock or variable proportioning brake system), and the test procedures for these requirements are set forth in S7.9 and S7.10. GM Proposed Interpretation 4: The subject brake system is a 'split service brake system' consisting of four subsystems--one at each wheel. Standard No. 105 specifies different partial failure requirements depending on whether a vehicle is manufactured with a split service brake system. The term 'split service brake system' is defined in S4 as 'a brake system consisting of two or more subsystems actuated by a single control designed so that a leakage- type failure of a pressure component in a single subsystem (except structural failure of a housing that is common to two or more subsystems) shall not impair the operation of any other subsystem.' We agree that your planned vehicle can be viewed as having four subsystems, one at each wheel. In only two of the subsystems, however, can leakage-type failures occur (the two hydraulic subsystems). Thus, in determining whether the vehicle has a split service brake system within the meaning of Standard No. 105, the key is whether a leakage-type failure of a pressure component in either of those two subsystems (except structural failure of a housing that is common to two or more subsystems) impairs the operation of any other subsystem (i.e., the other hydraulic subsystem or either of the two other subsystems). After reviewing the information provided with your letter, we have no reason to doubt that your planned system qualifies as a split service brake system. GM Proposed Interpretation 5: The four service brake subsystems may be certified to the requirements of S5.1.2 in accordance with the test procedure of S7.9.1 through S7.9.3 by disabling each subsystem in a way that does not affect the other three subsystems. Standard No. 105's requirements for partial failure are set forth in S5.1.2. For vehicles with a split service brake system, 5.1.2.1 provides that, in the event of a rupture or leakage type of failure in a single subsystem, other than a structural failure of a housing that is common to two or more subsystems, the remaining portion(s) of the service brake system shall continue to operate and shall be capable of stopping a vehicle from 60 mph within specified stopping distances. You suggested that certification of the requirements of S5.1.2.1, consistent with the procedure of S7.9.1 through S7.9.3, should be established by disabling each of the four subsystems in turn. You also stated that, for purposes of compliance testing, the subsystems would be disabled in such a way that the functioning of only one subsystem would be affected. It is our opinion that, in testing under S5.1.2.1, only the two hydraulic subsystems of your planned brake system would be disabled, as S5.1.2.1 only addresses rupture/leakage types of failures. It does not address any type of failure of a subsystem for which a rupture or leakage type failure cannot occur. We would not consider a break in an electrical system to be a 'rupture' within the meaning of Standard No. 105. We are uncertain as to the meaning of your statement that, for purposes of compliance testing, the subsystems would be disabled in such a way that the functioning of only one subsystem would be affected. This could be read as meaning that the agency must induce a rupture or leakage type failure in a place that doesn't affect other subsystems. However, under S7.9.1, any one rupture or leakage type of failure is introduced, other than a structural failure of a housing that is common to two or more subsystems. If any such leakage type failure impaired another subsystem, the brake system would not, of course, be considered a split service brake system within the meaning of Standard No. 105. GM Proposed Interpretation 6: The GMEV brake system may be certified to the requirements of S5.1.3 in accordance with the test procedure of S7.10 by functionally disabling the BCU. Such a procedure will completely disable the brake power assist, and since the electric motors within the hydraulic unit and the rear brake drums are separately disabled during S5.1.2 testing, there is no need to separately consider these electric motors when certifying to the requirements of S5.1.3. Standard No. 105's requirements for inoperative brake power assist unit or brake power unit are set forth in S5.1.3. You stated that your planned brake system would not utilize conventional power assist, but brake power assist would be provided by the combination of the BCU and four electric motors. You stated that this design does not lend itself to an obvious way of distinguishing brake power assist from other service brake subsystem components, and suggested that the brake system be certified to the requirements of S5.1.3 by disabling the BCU (which would disable all four electric motors and completely eliminate functional brake power assist) and then satisfying the provisions of either S5.1.3.1, S5.1.3.2, or S5.1.3.4. You also sought the agency's concurrence that there is no need to otherwise take the four electric motors into account when certifying to the requirements of S5.1.3. S4 of Standard No. 105 defines the term 'brake power assist unit' as a device installed in a hydraulic brake system that reduces the operator effort to actuate the system, and that if inoperative does not prevent the operator from braking the vehicle by a continued application of muscular force on the service brake control. Under the options of S5.1.3.1, S5.1.3.2, and S5.1.3.4, stopping distance requirements must be met with one brake power assist unit inoperative. We believe that each electric motor comes within the definition of 'brake power assist unit.' In addition, given the integrated nature of the BCU and the four electric motors, we believe that the combination of the BCU/four electric motors also comes within the definition of 'brake power assist unit.' It is therefore our opinion that the requirements of S5.1.3 must be met both when the BCU is disabled (which would disable all four electric motors and completely eliminate functional brake power assist) and also when each of the four electric motors is disabled individually. We note that, under our interpretation of S5.1.2 discussed above, not all of the four electric motors are separately disabled during S5.1.2 testing. GM Proposed Interpretation 7: The GMEV brake system may be certified to the requirements of S5.5 in accordance with the test procedure of S7.9.4 by functionally disabling the BCU. Since such a procedure will completely disable ABS and the variable proportioning function, no other testing is required in connection with S5.5. Standard No.105's requirements for failed antilock and variable proportioning brake systems are set forth in S5.5. You stated that the BCU is the functional power source for the GMEV's ABS, and that the BCU also regulates the proportion of front to rear braking. You sought the agency's concurrence that disabling the BCU is the appropriate means of complying with S5.5, and is consistent with the procedure of S7.9.4. S5.5 provides that a vehicle shall meet certain stopping distance requirements in the event of failure (structural or functional) in an antilock or variable proportioning brake system. S7.9.4 provides the following test procedure: With vehicle at GVWR, disconnect functional power source, or otherwise render antilock system inoperative. Disconnect variable proportioning brake system. Make four stops, each from 60 mph. If more than one antilock or variable proportioning brake subsystem is provided, disconnect or render one subsystem inoperative and run as above. Restore system to normal at completion of this test. Repeat for each subsystem provided. We concur that your planned brake system should be tested to the requirements of S5.5 in accordance with the test procedure of S7.9.4 by functionally disabling the BCU, and that no other testing is required. Under S7.9.4, the antilock system is to be rendered inoperative and the variable proportioning system is to be disconnected. Both of these procedures are accomplished by functionally disabling the BCU. Further, it is our opinion that the planned brake system would not have antilock or variable proportioning subsystems, since antilock at all four wheels and variable proportioning are all controlled by the BCU. GM Proposed Interpretation 8: Assuming the conditions established in proposed S6.2, regenerative braking is permitted to function normally when conducting the test procedures of S7. In particular, the phrase 'service brakes shall be capable of stopping' (found in S5.1.4 and S5.1.5, for example) is not to be construed as prohibiting the normal operation for regenerative braking. In addressing how the current requirements of Standard No. 105 would apply to your vehicle, we cannot assume the conditions you recommend establishing in a new S6.2. The agency would need to add those conditions to the standard in rulemaking. I will therefore address how regenerative braking would be treated under the current requirements. As discussed in your letter, regenerative braking assists in decelerating the vehicle by converting the kinetic energy of the moving vehicle into stored electrical energy within the vehicle's battery pack. Regenerative braking on the planned GM electric vehicle will supplement, under certain conditions, the friction braking provided by the service brakes. You stated that regenerative braking will only be available when the vehicle is 'in gear.' Since the large majority of Standard No. 105 tests are conducted with the vehicle in 'neutral,' regenerative braking will have no influence on the outcome of those tests. You indicated that since some Standard No. 105 tests, notably fade and recovery and the water test, are conducted with the the vehicle 'in gear,' regenerative braking could occur during these tests. You stated that you believe that regenerative braking should generally be allowed to function normally during Standard No. 105 testing. You argued that the regenerative braking which may occur during 'in gear' Standard No. 105 tests is little different from the engine braking which occurs in conventional ICE vehicles. We agree that regenerative braking should function normally during Standard No. 105 testing, just as engine braking occurs normally during Standard No. 105's 'in gear' tests. Another issue that you raised in connection with regenerative braking is the state of battery charge during testing, which can affect the amount of regenerative braking. You proposed (for your recommended new S6.2) that tests be initiated with a full charge of the vehicle's battery pack, so that the amount of regenerative braking that would occur during the tests would be minimized to the least amount that could occur in real world driving, i.e., the tests would be conducted under 'worst case' conditions. While Standard No. 105 specifies many test conditions, it does not specify state-of-battery charge. In an interpretation letter to Mazda dated October 2, 1990, we provided general guidance concerning how NHTSA interprets a standard where it does not specify a particular test condition. First, we stated that, in the absence of a particular test condition, we believe there is a presumption that the requirements need to be met regardless of such test condition, since the standard does not include any language which specifically limits applicability of its requirements to such test condition. We also indicated, however, that before reaching such a conclusion, we also consider the language of the standard as a whole and its purposes. It is our opinion that the braking requirements of Standard No. 105 must be met regardless of the state of battery charge. The purpose of Standard No. 105 is to ensure safe braking performance under normal and emergency conditions. Since an electric vehicle will be driven with the battery at various states of charge, safe braking performance can only be ensured if the standard's requirements can be met in all such conditions. This would generally be consistent with GM's suggestion that compliance testing be conducted under 'worst case' conditions. GM Proposed Interpretation 9: In addition to the explicit conditions for activation of the brake telltale set forth in S5.3 of the standard, permit illumination of the service brake telltale when an impending or latent brake system malfunction is detected during electrical diagnosis. As noted by your letter, S5.3.1 of Standard No. 105 requires a brake telltale to illuminate when there is a gross loss of hydraulic pressure (or, alternatively, a drop in fluid level), a total functional electrical failure in the antilock or variable proportioning brake system, and when the parking brake is applied. You stated that a brake telltale on the planned GMEV would illuminate under these prescribed conditions. You indicated, however, that a diagnostic capability will also exist to detect other faults in the brake system, and requested the agency's concurrence that S5.3.1 permits illumination of the brake telltale when other faults are detected which increase the likelihood of a substantial degradation in brake system performance. While Standard No. 105 requires that a brake telltale be provided which activates under certain specified conditions, it does not expressly state whether the required telltale may also be activated under other conditions. It is our opinion that the telltale may also activate under other conditions so long as such activation does not obscure or confuse the meaning of the required telltale or otherwise defeat its purpose. I note that this test is similar to one the agency has long used in addressing the issue of whether additional information may be provided along with information that is required to be labeled on certain products in the context of our safety standards. See, for example, NHTSA's December 20, 1991 interpretation letter to GM concerning Standard No. 209. The purpose of the brake telltale is to warn the driver of one of two conditions: (1) the parking brake is applied (and hence should be released before driving), or (2) the brake system has a significant fault which should be corrected. Since the additional conditions for activation which GM contemplates would represent significant brake system faults which should be corrected, it is our opinion that activation of the brake telltale under such conditions would not in any way defeat the purpose of the brake telltale. I hope you find this information helpful. If you have further questions, please contact Edward Glancy of my staff at this address or by telephone at (202) 366-2992. Sincerely, Paul Jackson Rice Chief Counsel"; |
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ID: aiam5651OpenDorothy Jean Arnold, M.D. 15 Fairview Knoll N.E. Iowa City, Iowa 52240-9147; Dorothy Jean Arnold M.D. 15 Fairview Knoll N.E. Iowa City Iowa 52240-9147; "Dear Dr. Arnold: This responds to your letter asking whether the ai bags in your car can be disconnected. You explained that you are physically impaired by the effects of osteomyelitis, a disease of the bones, cannot use a seatbelt with comfort, and were granted dispensation from such usage several years ago. In a telephone conversation with Richard Reed of this agency, you indicated that you are 74 years old, 5 feet, three inches tall, and must sit close to the steering wheel because of your medical condition. As explained below, our answer is that NHTSA will not institute enforcement proceedings against a repair business that disconnects an air bag on your vehicle to accommodate your condition. Standard No. 208, Occupant Crash Protection, requires that cars be equipped with automatic crash protection at the front outboard seating positions. The air bags in your car were installed as one means of complying with that requirement. The removal or deactivation of one of those air bags by a vehicle dealer is governed by a provision of Federal law, 49 U.S.C. 30122. The section provides that: A manufacturer, distributor, dealer, or motor vehicle repair business may not knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard. However, in limited situations in which a vehicle must be modified to accommodate the needs of a person with a particular disability or a person's special medical needs, NHTSA has in the past stated that it would consider violations of the 'make inoperative' prohibition as purely technical ones justified by public need, and that it would not institute enforcement proceedings. I would like to caution you that both safety belts and air bags are very important items of safety equipment. Safety belts are the primary means of occupant restraint, and work in all types of crashes. NHTSA estimates that in 1994, safety belts saved almost 9,200 lives and prevented more than 211,000 moderate to critical injuries. The combination of wearing safety belts and having an air bag installed at a seating position provides vehicle occupants with maximum safety protection in all types of crashes. Also, air bags are designed to offer some protection even when safety belts are not used. Since 1987, air bags are estimated to have saved 911 lives. NHTSA strongly encourages vehicle occupants to wear their safety belts, since we are concerned about the much higher safety risk faced by unbelted occupants. We understand, however, that you cannot wear your safety belt for medical reasons, and that you are concerned about a possible safety risk from the air bag in such a situation. While air bags have an impressive overall performance record and are designed to provide some protection even for unbelted occupants, NHTSA has become aware of situations in which current air bags have undesired side effects. These include situations in which an air bag appears to have contributed to serious injuries and even death to vehicle occupants, in minor-to-moderate severity crashes. Information indicates that an air bag might pose a risk of serious injury to unrestrained small statured and/or older people, in particular. I note that NHTSA has recently issued a request for comments (copy enclosed) concerning the agency s actions to minimize the adverse side effects of air bags and to invite the public to share information and views with the agency. Since your disability prevents you from wearing your safety belt, and given your age and size, the disability places you in a situation where there may be a risk of serious injury from the air bag. While this particular risk can be addressed by disconnecting the air bag, there are trade-offs: Disconnecting the air bag subjects you to a higher risk in crashes, especially higher-speed crashes, where the air bag would provide protection. We urge you to carefully weigh the trade-offs in making your decision. If you decide that the risk to you from the air bag offsets the potentially life-saving benefits of the air bag, and you wish to have your air bag deactivated, we would regard the deactivation a purely technical violation of the 'make inoperative' prohibition justified by public need. Accordingly, we would not institute enforcement proceedings against any person listed in section 30122 who deactivated the air bag. I would recommend that the manufacturer of the vehicle and/or air bag be consulted on the safest way to disconnect the air bag. I also note that the air bag should only be disconnected from a position where you would be seated. In addition, I strongly encourage you to ensure that every person in your vehicle who can use his or her safety belt does so. I want to add a caution. The purpose of the 'make inoperative' prohibition is to ensure, to the greatest degree possible, current and subsequent owners and users of your vehicle are not deprived of the maximum protection afforded by the vehicle as newly manufactured. Accordingly, if you were to sell your vehicle later, we urge that the air bag be reactivated for the subsequent driver. I hope that this letter resolves your problem. If you have any other questions, please contact Edward Glancy of my staff at this address or by phone at (202) 366-2992. Sincerely, Samuel J. Dubbin Chief Counsel Enclosure"; |
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Request an Interpretation
You may email your request to Interpretations.NHTSA@dot.gov or send your request in hard copy to:
The Chief Counsel
National Highway Traffic Safety Administration, W41-326
U.S. Department of Transportation
1200 New Jersey Avenue SE
Washington, DC 20590
If you want to talk to someone at NHTSA about what a request for interpretation should include, call the Office of the Chief Counsel at 202-366-2992.
Please note that NHTSA’s response will be made available in this online database, and that the incoming interpretation request may also be made publicly available.