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: aiam2420OpenMr. G. B. Craig, Commissioner, Department of California Highway Patrol, P.O. Box 898, Sacramento, CA 95804; Mr. G. B. Craig Commissioner Department of California Highway Patrol P.O. Box 898 Sacramento CA 95804; Dear Commissioner Craig: Thank you for your August 12 and September 28, 1976, letters to ou Office of Standards Enforcement concerning possible noncompliance of certain air- braked school buses with Standard No. 121, *Air Brake Systems*. At issue is the functioning of a 'double check valve' between the two tanks of an air brake system designed to meet S5.7.2 of the standard (as it was in effect prior to September 1, 1976). The valve serves to provide air pressure from either supply reservoir to hold off the spring brakes while guarding the air brake system from air loss through either one of the reservoirs. The identified problem stems from construction or installation of the valve such that it does not necessarily operate to seal off the brake system from a loss of air in one of the tanks, permitting loss of air from both reservoirs unless the rate of air loss is substantial. Your letter advises that the State of California is permitting the continued operation of the school buses in question pending receipt of a response from the National Highway Traffic Safety Administration (NHTSA).; I would like to address the findings you raise in the order in whic they are listed on page two of your letter. I interpret your first finding to be that the 'split system' designs used in compliance with Standard No. 121 may be incapable of meeting the stopping distance requirements set forth in S5.7.2. You question whether S5.7.2 adequately specifies a 'back up' braking capability that is not cancelled out by a single failure of air pressure components, citing cases where a substantial rate of loss from one tank (introduced as a failure in accordance with S5.7.2.3) draws down the air pressure in both halves of a split system.; The general requirement of S5.7.2.3 (of the now superseded text) i that the vehicle, in one out of six attempts under specified conditions, must be capable of stopping from 60 mph within a distance of 613 feet 'with a single failure in the service brake system of a part designed to contain compressed air or brake fluid. . . .' To provide this performance (and meet the other requirements of S5.7.2) manufacturers have provided 'split systems' modulated by the service brake control. As a matter of general compliance with this requirement, you have asked if any single failure (other than failure of common components) can be introduced into the system as a test of its compliance. The answer to your question is yes. The NHTSA does not know the basis of Ford Motor Company's contention that the 'failure' introduced in the system must be at least 50 psi/min from an initial reservoir pressure of 120 psi.; A noncompliance with S5.7.2.3 occurs only if the vehicle, with th failure introduced, is incapable of stopping within the prescribed distance in one out of six attempts. Thus, an extremely small failure which is easily overcome by compressor pressure would be one way of testing for compliance with S5.7.2.3, but it would not, in all likelihood, result in the demonstration of a noncompliance. As you noted in the second paragraph of page 3 of your letter, a noncompliance with stopping distance requirements may depend (largely because of a compressor's ability to overcome air loss) on the rate of leakage introduced and the time allowed between introduction of the failure and application of the emergency brake. The standard does not (except for the provision of S6.1.14 for towing vehicles manufactured on or after September 1, 1976) provide detailed specification of procedures, particularly the time between failure and brake application. The agency therefore must utilize a reasonable procedure that does not unfairly test the system. In this case, the agency considers the introduction of any size leak, followed by brake application as soon as the low pressure warning activates, to be a reasonable procedure, approximating what would occur in the event of actual failure on the highway. The agency would find a noncompliance with S5.7.2.3 if the school buses are incapable of stopping within the required distance when the described procedure is followed.; Your second finding is that a particular double check valv installation can cause noncompliance with S5.7.2.3. Consistent with our general discussion of compliance with S5.7.2.3, stopping tests are the means to discover whether the buses in question comply. We are analyzing your data, and a noncompliance investigation has been opened. We have notified Ford Motor Company of its commencement. We have also forwarded data to our Office of Defects Investigation to see if the check valve problem constitutes a safety-related defect apart from the issue of compliance.; Your last three findings address the separate question of whether th concept of a split system is adequately interfaced with the parking brake requirements of Standard No. 121. First you make the general point that, if S5.7.2.3 permits a substantial loss of air from both sides of a split system, the benefit of redundant lines is negated and the split system requirement is unjustified. The agency understands your position and believes that a stricter control on the amount of permissible leakage (perhaps by means of a limitation on compressor replenishment or a longer period before emergency brake application) may be justified. Particularly important is your point that a compressor loses capability as it grows older, and that this is not accounted for in new-vehicle tests. At the same time, however, larger failures do occur and we continue to view the split system as extremely important for these cases. The split system provides extremely good protection against failures such as rupture of a line or brake chamber diaphragm.; With regard to your point that split systems do not guard agains failure of components common to the two systems as they are presently constructed (such as the compressor drive belt), I must agree with your point that no brake system can guard against every conceivable failure completely. It is for these cases, in fact, that the agency considers the automatic application of the parking brake system beneficial following loss of the other two capabilities.; You make the further point that, in cases of marginal compliance (i.e. the compressor can replace most but not all air loss from both sides of the split system), the gradual loss of system pressure permits parking brake application that interferes with modulation of the emergency capability. While S5.7.2 was designated as '*Modulated emergency braking system*', no specification for modulation was set forth in its requirements. The agency intended that a system conforming to S5.7.2 would be controlled by the driver instead of by automatic application. Our review of the systems you tested indicates that they are 'modulated systems' as contemplated by the agency.; The present emergency brake requirements only state that the system 'b applied and released, and be capable of modulation, by means of the service brake control.' While further specification of this requirement may be in order, I believe it is the early application of the parking brake that actually concerns you, as it affects the application and release of the emergency braking capability.; You make the observation that early application of the spring brakes i response to air pressure loss permits them to drag, become overheated, and fade, making them useless before they can be utilized. A related issue is that the spring brakes will apply shortly after emergency brake availability (even before activation of the low air pressure warning), immobilizing the vehicle with no capability to release the parking brakes. You suggest implementation of a parking brake arrangement that would keep the spring brakes off longer or provide an isolated source of air pressure to permit their release when they do lock up.; Analysis of your test reports leads me to agree that some specificatio to limit the early application of spring brakes would be in order. Of course, as you are well aware, notice to interested persons of any change in the standard is required, along with an opportunity for comment. I believe that such rulemaking could be joined with the earlier rulemaking undertaken in response to a California Highway Patrol (CHP) petition (Docket 75-16, Notice 04).; Your final point is that, as long as early application of the parkin brake is permissible, an isolated tank of air should be available to permit release of the parking brake from the driver's position. With regard to an isolated tank, the NHTSA continues to maintain its view set forth in our November 29, 1974, letter to Donald Gibson of the CHP that the second side of the split system provides more capability than the old systems (with an isolated tank) to avoid a lockup following a service brake failure. However, you have clearly demonstrated that the capability can be essentially negated by early application of the parking brake. I believe that limitations on early application of the parking brake would be a superior correction to the problem than the addition of more components (and complexity) to the existing systems.; Because school buses are involved in the problems you cite, you are n doubt aware that S 103(d) of the National Traffic and Motor Vehicle Safety Act, while preemptive of State regulations or laws of general applicability that are not identical to Federal standards on the same aspect of performance, does not prevent a State or political subdivision from specifying a higher level of brake performance in vehicles 'procured for its own use.' Thus, the State of California may wish to order school buses with the additional isolated reservoir that you have recommended. The addition of a third tank to a system that complies with the standard's requirements would not be prevented by S 103(d).; I appreciate the constructive approach being pursued by the State o California in enforcement of Standard No. 121. Our Office of Standards Enforcement will keep you advised of the results of its investigation.; Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicl Programs; |
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ID: aiam2070OpenMr. John Lomash, United States Testing Co., Inc., 1415 Park Avenue, Hoboken, NJ 07030; Mr. John Lomash United States Testing Co. Inc. 1415 Park Avenue Hoboken NJ 07030; Dear Mr. Lomash: This is in response to your letter of September 11, 1975, in which yo asked whether Standard No. 217 requires a minimum retention or force in pushing out an emergency exit window after activation of the release mechanism.; You should note that the force applications specified in S5.3.2 fo operation of the release mechanism and subsequent extension of the exit by an occupant are maximum requirements. Therefore, a push-out window which only requires enough force to lift the glass and subframe following operation of the release mechanism complies with the requirements of S5.3.2 and S5.4 as long as that force does not exceed the levels specified for the particular reach distance of the release mechanism.; The standard specifies no minimum force requirements for either th operation of the release mechanism or the extension of the exit following release.; Sincerely, Frank A. Berndt, Acting Chief Counsel |
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ID: aiam4848OpenMr. Stanley L. Dembecki 2303 N. 44th Street, #14-237 Phoenix, AZ 80058; Mr. Stanley L. Dembecki 2303 N. 44th Street #14-237 Phoenix AZ 80058; Dear Mr. Dembecki: This responds to your letter of March 1, 1991 asking for an 'evaluation' of your 'Flashing' center stop lamp. You have four prototypes: 'complete' one and two bulb units 'for l984 and older vehicles', and one and two 'electronic modules for all third safety brake light retrofits through 1991.' In your opinion, 'since the new safety brake light utilizes the existing brake light (retrofit) on a previously approved brake light assembly it is reasoned that any evaluation as to durability testing is not really needed.' We understand that your 'complete' unit for the older vehicles is a lamp. It is unclear whether the 'electronic module' intended for retrofit for newer vehicles is a separate lamp, or a device to be inserted into an existing lamp. However, the issue that your invention presents is not whether further testing of it is required, but whether it is permitted at all under applicable Federal statutes and regulations. We note that you would like to market it both for installation in passenger cars that already have a center lamp, and in those that do not. In short, you intend to sell the lamp/module in the aftermarket for installation on vehicles in use, rather than as original equipment installed by the manufacturer. Center highmounted stop lamps have been required by Federal Motor Vehicle Safety Standard No. 108 on all passenger cars manufactured on or after September 1, l985 (effectively the l986 model year). You indicate that your lamp flashes momentarily when the brake pedal is applied and thereafter the lamp is steady-burning. Standard No. 108 initially allowed the center lamp to be wired so as to flash with the turn signals but, since September 1, l986, has required the center lamp to be steady-burning at all times when in use. Because your invention is not steady-burning at all times, and is activated by the brake pedal and not the turn signal control, the sale or installation of the invention may be prohibited by Federal law. If this invention is a lamp, it is not a center lamp that conforms to either the initial or current requirements of Standard No. 108 for center lamps. If, on the other hand, it is a module intended for insertion into an existing lamp, its sale or installation could violate existing Federal requirements. The National Traffic and Motor Vehicle Safety Act forbids the sale of equipment that does not comply with a Federal motor vehicle safety standard. If your invention is sold as a lamp, and intended to replace original equipment center lamps on l986 and subsequent model year cars, its sale would be in violation of the Act. On the other hand, there is no similar prohibition on sale of componentry such as an electronic module that would create a noncompliance once installed. However, there is a prohibition on the installation of such componentry (as well as installation of the invention in lamp form on l986 and subsequent model year cars). The Act forbids a manufacturer, distributor, dealer, or motor vehicle repair business from rendering inoperative in whole or in part any equipment on a vehicle which has been installed pursuant to a Federal motor vehicle safety standard. We interpret this as forbidding the installation of equipment that would take a vehicle out of compliance with a Federal safety standard. With respect to l985 model and older cars, which Standard No. 108 did not require to be equipped with center lamps, sale of your lamp exclusively for use on these older vehicles would not violate the Act. However, its installation remains subject to the rendering inoperative prohibition discussed above. There are other Federal standards involving equipment to consider. For example, we would be concerned if your lamp interfered with the field of view of the interior rear view mirror, and if its installation would affect the wiring of the other stop lamps so as to interfere with their design performance. However, there should be no problem with the field of view requirements if the lamp size is comparable to the required center lamps. Once you have satisfied these concerns under Federal law, use of the lamp remains subject to the laws of the individual States in which it is used. We are unable to advise you on these laws, and suggest that you consult for an opinion the American Association of Motor Vehicle Administrators, 4600 Wilson Boulevard, Arlington, Va. 22203. Sincerely, Paul Jackson Rice Chief Counsel; |
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ID: aiam2565OpenMr. Richard L. Kreutziger, Executive Vice President, Coach & Equipment, P. O. Box 36, Penn Yan, NY 14527; Mr. Richard L. Kreutziger Executive Vice President Coach & Equipment P. O. Box 36 Penn Yan NY 14527; Dear Mr. Kreutziger: This responds to your March 15, 1977, letter asking whether the hea and knee form impact requirements of Standard No. 222, *School Bus Passenger Seating and Crash Protection*, apply to the stanchion post and cross bars installed in your buses.; School buses with gross vehicle weight ratings of 10,000 pounds or les are not required to have restraining barriers as mandated in S5.2 of the standard for larger buses. Therefore, there is no requirement that you install stanchions, cross bars, or panels in the buses you manufacture. Should you choose to install these devices, they would not be required to be as wide as the seat. Similarly, there would be no requirement pertaining to forward or rearward movement of these devices.; The leg protection zone as defined in S5.3.2 of the standard i measured with reference to seat backs and restraining barriers. Since the devices you mention are not considered as either seat backs or restraining barriers, the leg protection zone requirements do not apply.; The head protection zone requirements, on the other hand, apply to an contactable surface located within the zone defined in S5.3.1 of the standard. Since part of the stanchion to which you refer creates a contactable surface within the head protection zone, it must meet the requirements of the standard specified in S5.3.1.; Sincerely, Frank Berndt, Acting Chief Counsel |
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ID: aiam0558OpenRoman G. Burnor, Esq., Counsel, Lamp Division, General Electric Company, Nela Park, Cleveland, OH 44112; Roman G. Burnor Esq. Counsel Lamp Division General Electric Company Nela Park Cleveland OH 44112; Dear Mr. Burnor: This is in reply to your letter of December 21 to Mr. Vinson of thi office asking for confirmation of your understanding that manufacturers of bulbs for 'automotive replacement lamps and devices' are not required to certify compliance with Federal Motor Vehicle Safety Standard No. 108.; Standard No. 108 establishes performance requirements for items o motor vehicle lighting equipment, and incorporates by reference certain SAE standards that specify requirements lamps must meet in laboratory tests when assembled. The SAE standard that applies to bulbs, J573d, *Lamp Bulbs and Sealed Units*, is not incorporated by reference, and Standard No. 108 contains no requirements for the output of bulbs furnished with a lamp assembly. When a lamp is tested for conformity, the production bulb is removed and a calibrated bulb substituted, in accordance with Paragraph C of SAE Standard J575d, Tests for Motor Vehicle Lighting Devices and Components, the test bulb is to be 'representative of standard bulbs in regular production' and must be 'selected for accuracy in accordance with specifications listed in . . . SAE J573.'; In summary, Standard No. 108 does not specify performance requirement for lamp bulbs, and production bulbs are not used in lamp testing. Therefore, Standard No. 108 does not apply to bulbs and bulb manufacturers are not required to certify conformance to Federal standards, or to submit information pursuant to the *Manufacturer Identification* regulations.; Sincerely, Richard B. Dyson, Assistant Chief Counsel |
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ID: aiam2135OpenFile; File; On December 1, 1975, I received a telephone call from Mr. Nakajima o Bridgestone Tire Co. (213-320-6030) concerning the meaning of the March 1, 1975, effective date of Standard No. 119. He wanted confirmation that tires, for vehicles other than passenger cars, that were manufactured before that date are not subject to the standard's labeling requirements. I explained that his understanding was correct, citing 49 CFR S571.7.; Mark Schwimmer |
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ID: aiam0108OpenMr. Stephen E. O'Toole, National Highway Users Conference, National Press Building, Washington, DC 20004; Mr. Stephen E. O'Toole National Highway Users Conference National Press Building Washington DC 20004; Dear Mr. O'Toole:#Thank you for your letter of August 23, to Mr. Georg Nield, concerning the compliance of crane carriers and fire engines with Federal Motor Vehicle Safety Standards 103 and 104.#The crane carrier you have described is a 'motor vehicle' subject to the provisions of the National Traffic and Motor Vehicle Safety Act of 1966. For purposes of the Federal Motor Vehicle Safety Standards the described crane carrier is classified as a 'truck.' Although currently Federal Standards 103 and 104 do not apply to trucks both standards, by amendment, issued April 24, 1968, (33 F.R. 6466-69), will be applicable to trucks manufactured on or after January 1, 1969.#Similarly, a fire truck is a 'motor vehicle' and a 'truck' and subject to all Federal Motor Vehicle Safety Standards applicable to this category of vehicle, including Standards 103 and 104. However, the open cabs found on many fire trucks may make full compliance with Standard 103 impossible. A public docket, Docket No. 24, has been established to receive comments pertaining to the possible classification of fire fighting equipment as a separate vehicle category which might be exempt from certain standards.#Sincerely, Robert M. O'Mahoney, Assistant Chief Counsel for Regulations; |
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ID: aiam1349OpenMr. Gorou Utsunomiya, Branch Manager, Toyo Kogyo U.S.A., Suite 462, 23777 Greenfield Road, Southfield, MI 48075; Mr. Gorou Utsunomiya Branch Manager Toyo Kogyo U.S.A. Suite 462 23777 Greenfield Road Southfield MI 48075; Dear Mr. Utsunomiya: This is in reply to your letter of December 6 to Mr. Lewis Owen of thi Office concerning the use of a special parking lamp bulb in one of your tail lamp assemblies.; The location of the subject bulb in the lamp assembly, regardless o whether the switch is removed to make it inoperative, is permitted, providing that the other required lamps function as specified in Federal Motor Vehicle Safety Standard No. 108.; Sincerely, E. T. Driver, Director, Office of Operating Systems, Moto Vehicle Programs; |
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ID: aiam3374OpenMr. Clint Moye, Assistant Director, Motor Vehicle Division, State Revenue Department, Room 101, Trinity Washington Building, Atlanta, GA 30334; Mr. Clint Moye Assistant Director Motor Vehicle Division State Revenue Department Room 101 Trinity Washington Building Atlanta GA 30334; This is in response to your request on the adequacy of the Georgi certificate of title for use in lieu of a separate Federal odometer form.; As you know, the Federal odometer requirements that became effective a of January 1, 1978, have been substantially increased. We have made provision for those states that wish to include odometer information on their titles to use a shortened form that was adopted by the American Association of Motor Vehicle Administrators (AAMVA). We consider the AAMVA form to include the minimum amount of information ncessary for an adequate disclosure.; In addition to the information included on the sample title which yo submitted to our office, the buyer's signature is also required. If this signature is included, the title may be used in lieu of a separate Federal form.; Sincerely, John Womack, Assistant Chief Counsel |
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ID: aiam1719OpenMr. Helmuth von Beckman, Technical Director, Tamper, Inc., 2401 Edmund Road, West Columbia, SC 29169; Mr. Helmuth von Beckman Technical Director Tamper Inc. 2401 Edmund Road West Columbia SC 29169; Dear Mr. von Beckman: This responds to your November 22, 1974, request for a determination o whether Tamper Corporation's products qualify as motor vehicles subject to Standard No. 121, *Air brake systems*. All of the vehicles you describe are designed only for use on a rail or rails, except for the Kal-Trac switcher, which has both steel wheels for rail use and pneumatic tires for highway use.; I have enclosed a discussion of our regulatory authority over moto vehicles which explains that all of your products which operate exclusively on a rail or rails are not subject to our regulations.; In a December 9, 1974, telephone call with Mr. Herlihy of this office you stated that the Kal- Trac switcher has axles with a gross axle weight rating (GAWR) in excess of 29,000 pounds. I enclose a copy of an NHTSA proposal that would exempt such a vehicle from Standard No. 121. We will consider your letter as support for this proposal.; Please contact Mr. Herlihy by phone (202-426-9511) after January 15 1975, to be advised if this proposal has been made final as an exemption for your vehicles from the standard.; Yours truly, Richard B. Dyson, Acting Chief Counsel |
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Request an Interpretation
You may email your request to Interpretations.NHTSA@dot.gov or send your request in hard copy to:
The Chief Counsel
National Highway Traffic Safety Administration, W41-326
U.S. Department of Transportation
1200 New Jersey Avenue SE
Washington, DC 20590
If you want to talk to someone at NHTSA about what a request for interpretation should include, call the Office of the Chief Counsel at 202-366-2992.
Please note that NHTSA’s response will be made available in this online database, and that the incoming interpretation request may also be made publicly available.