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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 12031 - 12040 of 16515
Interpretations Date

ID: nht78-2.44

Open

DATE: 03/29/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Stanley Kuny

TITLE: FMVSS INTERPRETATION

TEXT: Joan Claybrook has asked that I respond to your February 24, 1978, letter asking whether the seller of a school bus that contains a safety-related defect is responsible for correcting the defect, whether the buyer would otherwise be entitled to a refund for the price of the defective equipment, and whether a brake pressure limiting valve may be installed on the front axles of school buses whose antilock systems are disconnected pursuant to a recall campaign. You also ask about the status of the reimplementation of requirements for school bus service brake stopping distance performance contained in Standard No. 121, Air Brake Systems.

Section 154 of the National Traffic and Motor Vehicle Safety Act (the Act) (15 U.S.C. 1414) requires the vehicle manufacturer to provide an adequate repair of safety-related defects found in its products, unless replacement of the vehicle or refund of its purchase price is undertaken. International Harvester (IH) is in the process of field-testing its remedy for these school buses and it should be available fairly soon.

As for the installation of front-axle brake pressure limiting valves, Federal regulations for vehicles in interstate commerce prohibit the installation of manual limiting valves in 121-equipped vehicles and regulate the installation of automatic limiting valves. Also, section 108(a)(2)(A) of the Act prohibits, with one exception, the knowing rendering inoperative by commercial facilities of a device or element of design installed in satisfaction of a Federal safety standard such as Standard No. 121. A private party is not prohibited under this provision, but the vehicle manufacturer should be consulted about safest configuration of the vehicle brake system. In this case, IH's notice on antilock disconnection explained that the deactivation would render the brake system identical to those produced by IH since the "no lockup" requirement was suspended in January 1976. Thus IH does not recommend any further modification of the brake system.

With regard to your belief that the antilock systems may have cost $ 1200.00, I would like to clarify that Standard No. 121 contains many requirements for improved braking, and the incremental price increase for the improved brakes is attributable only in part to the antilock systems. At present, the Kelsey-Hayes antilock system used on IH school bus chassis costs $ 412.11, and this price would presumably be lower if the system was installed on all bus production as standard equipment.

As for the status of the reimplementation of service brake stopping distance requirements for school buses on April 1, 1978, the NHTSA expects to reach a decision soon and publish it in the Federal Register. I have asked a member of my staff to call you when a decision is made public.

ID: nht78-2.45

Open

DATE: 01/06/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Arent, Fox, Kenter, Plotkin & Kahn

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your December 1, 1977, request for agreement by the National Highway Traffic Safety Administration that the installation as original or aftermarket equipment of an electric retarder on the driveline of an air-braked vehicle would not affect its compliance with Standard No. 121, Air Brake Systems.

Section 108(a)(1)(A) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1397(a)(1)(A)) requires, among other things, that no person manufacture or sell any motor vehicle manufactured on or after the date any applicable Federal motor vehicle safety standard takes effect unless it is in conformity with such standard. As your letter indicates, you are aware that this provision makes it impossible for the NHTSA to "approve" the compliance of a vehicle configuration in advance of manufacture of the vehicle, because there can be no certainty that the vehicle as manufactured will actually comply. In this case, for example, the retarder's weight or the manner in which it is mounted would affect the actual compliance of the vehicle in which it is installed.

Jacobs' September 20, 1977, analysis evaluated the likelihood that certain retarders to be imported or manufactured by Jacobs would affect compliance. With regard to these retarders, it appears that their installation as original equipment or in the aftermarket in the fashion described would not affect compliance of the vehicle with Standard No. 121. This finding is of necessity limited to the retarders evaluated in the September 20, 1977, analysis.

ID: nht78-2.46

Open

DATE: 01/26/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: AM General Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your December 12, 1977, request for confirmation that an air-braked electric trackless trolley may be tested for compliance with S5.3.1 of Standard No. 121, Air Brake Systems, with its transmission selector control in the "DRIVE" position if the drive wheels and motor are permanantly mechanically connected and the motor automatically provides retardation when the service brake control is depressed. Your other requests for interpretation have been answered by separate letters.

Section S6.1.3 of Standard No. 121 specifies:

S6.1.3 Unless otherwise specified, the transmission selector control is in neutral or the clutch is disengaged during all decelerations and during static parking brake tests.

This test condition does not permit testing for compliance with the transmission selector control in the "DRIVE" position. The performance levels of the standard were established at levels intended for the foundation brakes alone, exclusive of engine braking, and it is for this reason that the selector must be in neutral or the clutch disengaged. This is true both for vehicles with manual and automatic transmissions.

It does appear that a case may be made for testing the bus you describe with the selector in "DRIVE". One important factor would be whether the field in the motor generator is permanent or electrically induced. In the event you wish to petition for an amendment of S6.3.1, information of this nature should accompany your petition.

In response to your other question, the agency's July 10, 1974, letter to Flyer Industries remains valid.

ID: nht78-2.47

Open

DATE: 01/10/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Briskin Manufacturing Company

TITLE: FMVSS INTERPRETATION

TEXT: I would like to advise Briskin Manufacturing Company as a producer of air reservoirs for use on vehicles that comply with Standard No. 121, Air Brake Systems, that the National Highway Traffic Safety Administration (NHTSA) has decided to withdraw its December 14, 1977, interpretation of the requirement that reservoirs "withstand" internal hydrostatic pressure (copy of interpretation enclosed).

While the NHTSA simply intended to clarify its existing interpretation of the requirements, information brought to the agency's attention indicates that the revised interpretation would have the unintended effect of increasing the stringency of the requirements. Any such upgrading of the integrity requirements for air reservoirs would be preceded by notice and opportunity for public comment.

The agency expects to publish notice that its interpretation is withdrawn in the Federal Register in the near future.

ID: nht78-2.48

Open

DATE: 05/23/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: The Johnson Manufacturing Co.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Johnson Manufacturing's May 4, 1978 request for confirmation that the requirement in Standard No. 121, Air Brake Systems, that reservoirs "withstand" specific pressure does not require testing of a multi-compartment reservoir compartment-by-compartment.

Your understanding of the "withstanding" requirement in S5.1.2.2 and S5.2.1.3 is correct. Although the agency sought to clarify that compartment-by-compartment testing was the proper interpretation of this requirement (42 FR 64630; December 27, 1977), problems with the interpretation resulted in its withdrawal (43 FR 9149; March 6, 1978) and adherence to the existing interpretation that there be no rupture or permanent circumferential deformation of the reservoir. Under this interpretation only the circumference of the outer reservoir shell is measured, and internal baffles are not stressed by separate compartment-by-compartment testing.

ID: nht78-2.49

Open

DATE: 01/05/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Kelsey-Hayes Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Kelsey-Hayes' September 2, 1977, request to know whether Standard No. 121, Air Brake Systems, allows a burnish of the brake friction elements immediately prior to the parking brake tests of S5.6, and whether the service line air pressure limitation of 100 p.s.i. specified in S5.4.2.1 can be exceeded monentarily.

A burnish prior to the parking brake test is not permitted by Standard No. 121, except that S6.1.8 specifies burnish of the parking brake friction elements before testing in those cases where the parking brake system does not utilize the service brake friction elements. The National Highway Traffic Safety Administration (NHTSA) would consider a provision to deal with the condition of the brake linings prior to the parking brake test upon receipt of technical data showing justification for such an action.

Section S5.4.2.1 of the standard specifies a procedure that states "[the] service line air pressure shall not exceed 100 p.s.i. during any deceleration." You describe a condition in which the service line pressure exceeds 100 p.s.i. for a short period (typically 0.1 seconds), which might be traced to characteristics of the friction material, brake mechanism, dynamometer, or instrumentation.

The NHTSA recognizes that peak pressure may be momentarily increased by the initial rush of air pressure into the brake chamber, or by other anomolies. In the case of such momentary pressure increases, the NHTSA interprets S5.4.2.1 to mean that the source of air pressure for applying the brake must never exceed 100 p.s.i. Thus, it would be permissible to experience momentary pressures above 100 p.s.i. in the service line as long as the pressure source never exceeds that level. Sustained periods of pressure above 100 p.s.i. would not be permissible.

SINCERELY,

KELSEY-HAYES COMPANY

September 2, 1977

Joseph J. Levin, Jr. National Highway Traffic Safety Administration

RE: Request for Interpretation FMVSS-121, Air Brake Systems @ 5.3.1 Stopping Distance-Trucks and Buses

Kelsey-Hayes Company, a domestic manufacturer of motor vehicle equipment including antilock systems, requests an interpretation of the above referenced section of Standard 121.

It is the nature of newly manufactured braking systems to have residual coatings of various materials deposited upon the brake components together with surface irregularities as a result of the manufacturing process.

FMVSS-121, as well as FMVSS-105, allow for this by providing burnish stops to remove foreign substances and to condition brake linings at the outset of the testing sequence. In addition to the initial burnish, some test procedures including FMVSS-105 specify burnishing at specific intervals during the test.

Reburnishes at specific intervals are provided in recognition of the fact that a rapid series of test stops will generate high temperatures and cause surface glazing on the brake lining material. To accurately gauge the effectiveness of the braking system, FMVSS-105 allows the brakes to be reburnished before the parking brake test. While perhaps not intended by FMVSS-105, the snub burnish procedure has the effect of paralleling actual vehicle use as it is normal to expect a driver to apply the service brakes in a routine fashion prior to parking the vehicle. No identical language appears in FMVSS-121, although Table 1-Stopping Sequence does provide for a burnish in its initial step.

The authors of FMVSS-105 recognized the abnormal conditions which develop during the harsh testing sequence. Further, they recognized that lining surface glazing will impair the holding characteristics of a braking system, perhaps to the extent that an otherwise completely adequate design will fail this standard for an unintended reason.

It is with these thoughts in mind that Kelsey-Hayes Company respectfully requests an interpretation by the NHTSA as to whether step 1 of Table 1 of FMVSS-121 will allow a burnish of the parking brakes immediately prior to step 5-parking brake test.

Thank you for your consideration.

David M. Thompson

ID: nht78-2.5

Open

DATE: 11/28/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: Blue Bird Body Company

TITLE: FMVSS INTERPRETATION

TEXT:

NOV 28 1978

NOA-30

Mr. W. G. Milby Manager, Engineering Service Blue Bird Body Company P.O. Box 937 Fort Valley, Georgia 31030

Dear Mr. Milby:

This responds to your August 3, 1978, letter asking how to compute the area of a sample of a body panel when testing for compliance with Standard No. 221, School Bus Body Joint Strength.

In your letter, you suggest that the net cross-sectional area of the sample is determined by multiplying the width of the sample by its thickness and then subtracting the area of each discreet fastener hole. The National Highway Traffic Safety Administration agrees that this procedure yields the correct area of the sample, and is the method used by the agency in its compliance testing.

Sincerely,

Joseph J. Levin, Jr. Chief Counsel

August 3, 1978

Mr. Joseph J. Levin Chief Counsel National Highway Traffic Safety Administration Washington, D.C. 20590

Dear Mr. Levin:

The purpose of this letter is to seek confirmation of our interpretation regarding FMVSS 221, School Bus Joint Strength.

It is our understanding that in meeting the requirements of S5, that the area to be used for calculating purposes, when discreet fasteners are used, is the net area of the weakest joined body panel. We define the net area as the width of the sample multiplied by its thickness, less the projected area of each discreet fastener hole.

We look forward to receiving an early written confirmation of this interpretation.

Thank you.

Very truly yours,

W. G. Milby Manager, Engineering Services

sw

ID: nht78-2.50

Open

DATE: 01/20/78

FROM: AUTHOR UNAVAILABLE; F. Berndt for J. J. Levin, Jr.; NHTSA

TO: The Bendix Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Bendix Corporation's November 9, 1977, request for confirmation that S5.6.4 of Standard No. 121, Air Brake Systems, does not prohibit the use of a two-valve sequential means to release the parking brakes on a towed vehicle.

I have enclosed for your information two interpretations that address this question, stating that a two-valve sequential release is permissible under S5.6.4. I have also enclosed a copy of an outstanding rulemaking proposal that would standardize the parking brake control as specified in the Society of Automotive Engineers Recommended Practice J680b. I am unable to advise you whether the National Highway Traffic Safety Administration intends to make final this proposal.

I would also like to remind you of the requirement in S5.6.4 that "[the] control shall be identified in a manner that specifies the method of control operation." So long as different control arrangements are used, it is critical that the means of operation be clearly marked.

ID: nht78-2.6

Open

DATE: 08/23/78

FROM: AUTHOR UNAVAILABLE; F. Berndt for J. J. Levin, Jr.; NHTSA

TO: U. S. Suzuki Motor Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of August 10, 1978, asking for an interpretation of Motor Vehicle Safety Standard No. 108. You have asked "whether an aftermarket Class A reflex reflector can be installed in addition to the original Equipment Class A reflex reflector, that is, an existing part of the motorcycle's rear combination lamp assembly." You have stated that "both reflectors would be installed vertically on the motorcycles vertical centerline," and have commented that you understand "that two reflectors may be installed horizontally about the vertical centerline, but it is unclear to us whether they may both be installed one on top of the other, vertically, as this is not addressed in FMVSS #108."

You have misunderstood Standard No. 108. Table IV clearly states with respect to location of rear reflex reflectors on motorcycles that "if two are used on the rear, they shall be symmetrically disposed about the vertical centerline." This requirement precludes the use of two rear reflectors mounted above each other vertically on the vehicle's centerline if your fender extension is sold as an accessory on a motorcycle at the time of its first purchase for purposes other than resale.

Generally, however, Federal standards do not cover vehicles after their first purchase and an owner may modify his vehicle in any manner he chooses consistent with local law. Modification by dealers, distributors, and repair businesses are prohibited only if they "render inoperative" any device or element of design installed on a motor vehicle in accordance with a Federal safety standard. Although aftermarket installation of the fender with reflector by a dealer after a vehicle's sale would not be consistent with the reflector location requirements of Standard No. 108, we cannot say that it would "render inoperative" the reflector installed as original equipment. We therefore have no objection to you offering this component as an aftermarket accessory to be added after a vehicle's initial sale.

SINCERELY,

U.S. SUZUKI Motor Corporation

August 10, 1978

Joseph J. Levin, Esquire Chief Counsel National Highway Traffic Safety Administration

Re: Request for interpretation

Dear Mr. Levin,

The U.S. Suzuki Motor Corporation is considering the addition of a rear fender extension to its Suzuki aftermarket accessory line for one of its large motorcycles. The accessory fender extension in question has as a component a Class A reflex reflector. The motorcycle's existing Class A reflex reflector is part of the rear combination lamp assembly.

The problem we are encountering is with interpreting FMVSS #108, Table IV, Location of Required Equipment, as to whether an aftermarket Class A reflex reflector can be installed in addition to the original Equipment Class A reflex reflector, that is, an existing part of the motorcycles' rear combination lamp assembly.

Both reflectors would be installed vertically on the motorcycles vertical centerline. We understand that two reflectors may be installed horizontally about the vertical centerline, but it is unclear to us whether they may both be installed one on top of the other, vertically, as this is not addressed in FMVSS #108.

For demonstration purposes we are enclosing photographs that show one of our current motorcycles in its original state (#1) and two that show the aftermarket fender extension mounted on the motorcycle (#2, #3). We would appreciate your reply as to whether or not Suzuki can offer this fender extension with reflex reflector as an aftermarket accessory, and that if aftermarket installation of it would be permitted.

Thank you for your assistance in this matter.

F. Michael Petler Assistant Manager Safety & Legislation Dept.

ENCLS.

CURRENT MODEL MOTORCYCLE WITHOUT AND WITH ACCESSORY FENDER EXTENSION

Photograph #1 Motorcycle rear fender in original state "OEM"

Photograph #2 Motorcycle rear fender with accessory fender extension installed

Photograph #3 Motorcycle rear fender with accessory fender extension installed.

(Graphics omitted)

ID: nht78-2.7

Open

DATE: 10/31/78

FROM: AUTHOR UNAVAILABLE; S. P. Wood for J. J. Levin, Jr.; NHTSA

TO: Subaru of America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of September 12, 1978, with respect to Subaru's intention to offer "a retracting center auxiliary lamp" on one of its models. You have asked us to comment on the lamp's nomenclature, switching, and compliance problems.

The lamp in question is not an item of lighting equipment required by Federal Motor Vehicle Safety Standard No. 108 and may be added as standard equipment provided it does not impair the effectiveness of equipment that the standard does require. Whether this device would cause impairment we cannot say since you have told us nothing of its candle-power output or its color. If it is operable by a separate on/off switch it could be viewed as impairing the effectiveness of the headlights by causing the operator to use it and rely on it at a time when the headlamps should be in use. We have no opinion on what you should call the lamp.

Even if permissible and not prohibited under Federal lighting requirements we believe that you should be aware of possible problems at the State level. An auxiliary driving light similar to the one you describe (though positioned closer to the right headlamps) was offered as optional equipment on 1969 Dodge cars, named the "Super Lite", and intended to be used in conjunction with low beam headlights to increase the strength of the headlamp system without producing the glare effects associated with high beams. The States of New Hampshire, New York, and Vermont prohibited the lamp primarily because its bluish color was judged close to that of the color reserved for use on emergency vehicles (see Chrysler Corp. v. Rhodes, 294 F. Supp. 665 (1968) and Chrysler Corp. v. Tofany, 419 F.2d 499 (1969)). We therefore suggest that Subaru review its plans with State officials.

SINCERELY,

SUBARU OF AMERICA, Inc.

September 12, 1978

Joseph J. Levin, Jr. Chief Counsel National Highway Traffic Safety Administration U.S. Department of Transportation

Re: FMVSS 108

Dear Mr. Levin:

Subaru of America plans to offer as standard on our MPV, BRAT model, a retracting center auxiliary lamp. We request your office's comments to the following questions.

1. Can we call the center lamp an auxiliary driving lamp?

2. Can we use a single on/off switch for this lamp? Or must it be switched to be used only with bright beam headlamps?

3. What are the compliance problems, if any?

Paul Utans Assoc. Vice President Product Compliance

(Graphics omitted)

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.

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