ID: 12625.wkm

Mr. Pedro Matos
Quality Manager
CNB/CAMAC
Portugal

Dear Mr. Matos:

This responds to your telefax of October 23, 1996, to this office in which you asked two questions about Federal motor vehicle safety standard (FMVSS) No. 109, New Pneumatic Tires. You first asked why, in Table II of Appendix A, tires with a specified maximum load of 300 kiloPascals (kPa) are tested at a lower inflation pressure than tires for which the specified maximum load is 36 pounds per square inch (psi). You then asked why, in the kPa section of Table II, the test inflation pressures increase then decrease as the maximum kPa inflation pressures increase.

I have enclosed several notices that explain the reasons for these differing test inflation pressures. In 1977 Goodyear Tire & Rubber Company (Goodyear) and the Rubber Manufacturers Association (RMA) petitioned this agency to amend FMVSS No. 109 to permit production of a new P-type tire that was designed to use a higher maximum inflation pressure than the standard 240 kPa then permitted by the standard, but with no increase in load levels. In response to those petitions, this agency amended the standard to include a maximum permissible inflation pressure of 300 kPa because tires with higher inflation pressures have less rolling resistance which may result in increased fuel economy. However, since there would be no increase in load levels, the agency specified that the inflation pressures at which those tires would be tested would remain the same, that is, 180 and 220 kPa respectively (Enclosures 1 and 2).

Then in 1988, the European Tyre and Rim Technical Organisation (ETRTO) petitioned this agency to further increase the maximum inflation pressure, citing requests from member manufacturers. ETRTO petitioned this agency to amend FMVSS No. 109 to permit an inflation pressure of 340 kPa so that the standard maximum inflation pressure then in effect for reinforced tires, 280 kPa, could be increased for special performance requirements, but again, with no increase in tire load capacity. The agency granted the ETRTO petition citing the Goodyear/RMA petition as precedent. Again, because the requested higher inflation pressure carried no increase in load levels, the agency specified that the test pressures for the 340 kPa tires would remain at 220 and 260 respectively (Enclosures 3 and 4).

The latest maximum inflation pressure, 350 kPa, was added to the standard effective August 31, 1994. The test inflation pressures remain the same as the 240 and 300 kPa maximum pressures, namely 180 and 220 kPa respectively, for the same reasons as explained above (Enclosure 5).

I hope this explanation is helpful to you. For your information, I am also enclosing a copy of the latest version of FMVSS No. 109 (as of October 1, 1995) (Enclosure 6). If you have any further questions or need additional information with respect to our tire standards, please feel free to contact Walter Myers of my staff at this address or at (202) 366-2992.

Sincerely,

John Womack

Acting Chief Counsel

Enclosures

ref:109

d:12/5/96

ID: 24778rbm

Mr. Klaus Hillenbrand
Siemens Restraint Systems GmbH
Carl-Zeiss-Strasse 9
63755 Alzenau

Dear Mr. Hillenbrand:

This responds to your letter asking about the seat positioning procedure in S8.1.2 of Federal Motor Vehicle Safety Standard (FMVSS) No. 208, Occupant crash protection, and S6.3 of FMVSS No. 214, Side impact protection.The text of the two different provisions is the same. You have requested clarification of the seating procedure because your interpretation of the language in these two sections differs from an explanation of the language that was provided in a 1995 legal interpretation provided to Patrick Raher of Hogan & Hartson, L.L.P. I am pleased to provide a response.

The seat position specifications of FMVSS No. 208 (S8.1.2) and FMVSS No. 214 (S6.3) read as follows:

Adjustable seats are in the adjustment position midway between the forwardmost and rearmost positions, and if separately adjustable in a vertical direction, are at the lowest position. If an adjustment position does not exist midway between the forwardmost and rearmost positions, the closest adjustment position to the rear of the midpoint is used.

In your letter, you stated that you read this language to mean that the longitudinal midposition would be determined by moving the seat in the most forward and most rearward position without moving the height adjustment and then marking the midposition at the seat rails. Height adjustment would then be made to the lowest level without any readjustment of the seat rails. Your primary question is whether the reference for the longitudinal midposition must be measured at the seat rails (where determination of the most forward/rearward position would be independent of any height adjustment) or if it can be measured somewhere at the seat pan (where height adjustment could influence the most forward/rearward position).

As discussed in the 1995 interpretation, there are two conditions concerning how an adjustable seat is positioned in a crash test. The first condition, for the longitudinal position of the seat, is for the seat to be in the adjustment position midway between the forwardmost and rearmost positions, irrespective of seat height in those positions. The second condition is that the vertical position be in the lowest position obtainable with the seat in the longitudinal midposition. Depending on whether the vertical position is separately adjustable, this may or may not be the lowest achievable position for the seat in any of its longitudinal positions.

The critical issue is whether the longitudinal midposition is referenced along a longitudinal plane at the point midway between the forwardmost and rearmost positions of the seat at any height.The midposition is not qualified by height, so absolute forwardmost and rearmost positions are used to determine the midposition irrespective if height at those positions. The vertical position of the seat is only determined after the longitudinal midposition has been established.

The seat position specification does not require that the longitudinal midposition be referenced at the seat rail, or at any other specific location.Any place in the vehicle that allows for the accurate marking of the longitudinal midposition is acceptable.While many test laboratories may choose to mark the midposition at the seat rail, there is no requirement that they do so.

I hope you find this information helpful. If you have any other questions, please contact Rebecca MacPherson of my staff at this address or by phone at (202)366-2992.

Sincerely,

Jacqueline Glassman
Chief Counsel

ref:208
d.10/15/02

ID: nht79-1.46

DATE: 03/13/79

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Subaru of America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: I regret the delay in responding to your September 12, 1978, letter requesting interpretation of Federal Motor Vehicle Safety Standard 101-80, Controls and Displays. The responses to your specific questions regarding the compliance of your prototype monitor of vehicle systems are as follows:

1. When there is no problem with the vehicle systems included in the monitor, only the outline of a car is visible. The displays for items such as oil and electrical charge would not be illuminated. You asked if the monitor in its "no problem" model would comply with FMVSS 101-80. The answer is yes. There is no requirement that the displays be continuously illuminated.

2. On the monitor, the high beam symbol would be oriented so that it pointed upward. You asked whether this complies with the standard even though the symbol appears in Table 2 of the standard pointing to the left. The answer is yes. The requirement in section 5.2.3 that the display symbol appear preceptually upright to the driver was not intended to apply to the situation in which the symbol is used in conjunction with a car diagram of the type in your monitor. In such situations, it would be more confusing to place the symbol in the upright position than to orient the symbol so that it bears the same relationship to the diagram as the symbolized equipment does to the actual vehicle.

SINCERELY,

(Graphics omitted)

September 12, 1978

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

Dear Mr. Levin:

Subaru is designing a new instrument, monitor panel for future U.S. vehicle application. We are concerned about its compliance to the new FMVSS, SS101-80.

The new monitor panel will have a white lined symbol of a car, the front of the car will be at the top of the drawing. It will be on a dark green background. Telltale symbols and descriptive words will be within and around the car drawing as representative of functions or mal-function conditions. To identify a special condition a light-emitting devise will illuminate a symbol or symbol and words. At this time we request your approval on two issues as addressed below.

1. When the Subaru is being driven in daylight and there are no problems to cause any of the telltale devises to be illuminated, only the white outline of a car is visible. Our prototype monitor is shown in the enclosed photos. Photo "A" is representative of a "no problem" condition in daylight; is it in compliance to Standard 101-80?

2. We would like to display the high beam symbol and telltale in a different position than the standard, specifically, 90 degrees clockwise. We feel the repositioning of the high beam symbol will be more representative to the car outline with the head-lamps pointing ahead rather than to the left. The lamp to display a high beam "on" condition will be the color blue. Our photo "C" and diagram "E" demonstrates what we plan to do, particularly in regard to a high beam in "use" condition.

Does the above conform to FMVSS 101-80?

Paul Utans Assoc. Vice President Product Compliance

(Graphics omitted)

ID: nht94-2.9

TYPE: Interpretation-NHTSA

DATE: April 1, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Jane L. Dawson -- Specifications Engineer, Thomas Built Buses, Inc.

TITLE: None

ATTACHMT: Attached to letter dated 11/22/93 from Jane L. Dawson to Walter Myers

TEXT:

This responds to your letter to Walter Myers of this office in which you posed two questions regarding Federal Motor Vehicle Safety Standards (FMVSS) 217, Bus Window Retention and Release.

Your first question related to the definition of "daylight opening" found in the final rule amending FMVSS 217, dated November 2, 1992, (57 FR 49413) (hereinafter Final Rule). Specifically, you asked "(w)hat constitutes an obstruction and how close to t he door does an object have to be in order to be considered an obstruction?"

The term "daylight opening" is defined in the Final Rule as "the maximum unobstructed opening of an emergency exit when viewed from a direction perpendicular to the plane of the opening." An obstruction in this context would include any obstacle or obje ct that would block, obscure or interfere with, in any way, access to that exit when opened. In determining the "maximum unobstructed opening of an emergency exit," we would subtract, from the total area of the opening, the area of any portions of the o pening that cannot be used for exit purposes as a result of the obstruction. The area measurements would be taken when viewed from a direction perpendicular to the plane of the opening. I have enclosed a copy of a March 24, 1994 letter to Mr. Bob Carve r of Wayne Wheeled Vehicles which provides an example of how the amount of area to be credited was determined for a specific design.

You should be aware that the agency published a notice of proposed rulemaking to amend Standard No. 217 on December 1, 1993, (58 FR 63321). The notice proposed two alternate means for determining the maximum amount of area that will be credited for all types of emergency exits on school buses. The agency is currently reviewing the comments received in response to this notice. I am enclosing a copy of this notice.

In your second question you referred to the current provisions of S5.2.3.1(b), FMVSS 217, which provides that a left-side emergency door must be located in the rear half of the bus passenger compartment. You then asked whether that requirement was chang ed in the Final Rule. The answer is yes.

Section S5.2.3.1 of FMVSS 217, as amended in the Final Rule, provides manufacturers two options for the provision of school bus emergency exits, S5.2.3.1(a) (Option A) and S5.2.3.1(b) (Option B). Option A requires a rear emergency door. If additional e mergency exit area is required, the first additional emergency exit must be a left side door located as near as practicable to the midpoint of the passenger compartment. Option B requires a left-side emergency door and a pushout rear window, but does no t designate a specific location for them. Thus, the amended standard does not specify a location for a left-side emergency door installed for Option B, the equivalent of current S5.3.3.2(b).

I hope this information will be of assistance to you. Should you have any further questions or seek additional information, please feel free to contact Walter myers of my staff at this address or at (202) 366-2992.

ID: nht94-7.7

DATE: April 1, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Jane L. Dawson -- Specifications Engineer, Thomas Built Buses, Inc.

TITLE: None

ATTACHMT: Attached to letter dated 11/22/93 from Jane L. Dawson to Walter Myers

TEXT:

This responds to your letter to Walter Myers of this office in which you posed two questions regarding Federal Motor Vehicle Safety Standards (FMVSS) 217, Bus Window Retention and Release.

Your first question related to the definition of "daylight opening" found in the final rule amending FMVSS 217, dated November 2, 1992, (57 FR 49413) (hereinafter Final Rule). Specifically, you asked "(w)hat constitutes an obstruction and how close to the door does an object have to be in order to be considered an obstruction?"

The term "daylight opening" is defined in the Final Rule as "the maximum unobstructed opening of an emergency exit when viewed from a direction perpendicular to the plane of the opening." An obstruction in this context would include any obstacle or object that would block, obscure or interfere with, in any way, access to that exit when opened. In determining the "maximum unobstructed opening of an emergency exit," we would subtract, from the total area of the opening, the area of any portions of the opening that cannot be used for exit purposes as a result of the obstruction. The area measurements would be taken when viewed from a direction perpendicular to the plane of the opening. I have enclosed a copy of a March 24, 1994 letter to Mr. Bob Carver of Wayne Wheeled Vehicles which provides an example of how the amount of area to be credited was determined for a specific design.

You should be aware that the agency published a notice of proposed rulemaking to amend Standard No. 217 on December 1, 1993, (58 FR 63321). The notice proposed two alternate means for determining the maximum amount of area that will be credited for all types of emergency exits on school buses. The agency is currently reviewing the comments received in response to this notice. I am enclosing a copy of this notice.

In your second question you referred to the current provisions of S5.2.3.1(b), FMVSS 217, which provides that a left-side emergency door must be located in the rear half of the bus passenger compartment. You then asked whether that requirement was changed in the Final Rule. The answer is yes.

Section S5.2.3.1 of FMVSS 217, as amended in the Final Rule, provides manufacturers two options for the provision of school bus emergency exits, S5.2.3.1(a) (Option A) and S5.2.3.1(b) (Option B). Option A requires a rear emergency door. If additional emergency exit area is required, the first additional emergency exit must be a left side door located as near as practicable to the midpoint of the passenger compartment. Option B requires a left-side emergency door and a pushout rear window, but does not designate a specific location for them. Thus, the amended standard does not specify a location for a left-side emergency door installed for Option B, the equivalent of current S5.3.3.2(b).

I hope this information will be of assistance to you. Should you have any further questions or seek additional information, please feel free to contact Walter myers of my staff at this address or at (202) 366-2992.

ID: nht95-3.5

TYPE: INTERPRETATION-NHTSA

DATE: June 8, 1995

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Ron Hooker -- Missouri Department of Agriculture

TITLE: NONE

ATTACHMT: ATTACHED TO 5/9/95 LETTER FROM RON HOOKER TO JOHN WOMACK (OCC 10906)

TEXT: Dear Mr. Hooker:

This responds to your question about whether the State of Missouri has authority to promulgate regulations relating to the safety of motor vehicles powered by alternative fuels, particularly compressed natural gas (CNG). The short answer is that while M issouri is generally preempted in this area, it could issue its own more stringent safety standard for State-owned vehicles.

Federal law will preempt a State law if (1) there is a Federal safety standard in effect, (2) the State law covers the same aspect of performance as that Federal standard, and (3) the State law is not identical to the Federal standard. Specifically, sec tion 30103(b) of Title 49 of the United States Code states that

(b) Preemption - (1) When a motor vehicle safety standard is in effect under this chapter, a State or political subdivision of a State may prescribe or continue in effect a standard applicable to the same aspect of performance of a motor vehicle or motor vehicle equipment only if the standard is identical to the standard prescribed under this chapter. However, the United States Government, a State, or a political subdivision of a State may prescribe a standard for a motor vehicle or motor vehicle equip ment obtained for its own use that imposes a higher performance requirement than that required by the otherwise applicable standard under this chapter.

State safety standards applicable to CNG fuel system integrity are generally preempted by Federal law. The National Highway Traffic Safety Administration (NHTSA) has issued Federal motor vehicle safety standard (FMVSS) No. 303, Fuel system integrity of compressed natural gas vehicles. (59 FR 19659, April 25, 1994, copy enclosed). The Standard specifies frontal barrier and rear barrier crash tests conducted at 30 mph and a lateral moving barrier crash test conducted at 20 mph. The Standard applies to passenger cars, multipurpose passenger vehicles, trucks and buses that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less and use CNG as a motor fuel. It also applies to school buses regardless of weight that use CNG as a motor fuel. Th e Standard takes effect September 1, 1995. Accordingly, after September 1, 1995, Missouri could only issue its own safety standard applicable to CNG vehicle fuel system integrity if the State safety standard is identical to FMVSS No. 303. The one excep tion to requiring such identical standards is that Missouri could prescribe a standard for motor vehicles obtained for its own use, provided the State law imposed a higher performance requirement than the level of performance prescribed by FMVSS No. 303. Thus, Missouri could issue its own more stringent safety standard for State-owned vehicles.

NHTSA further notes that Missouri is free to issue safety standards applicable to the fuel system integrity of vehicles powered by other alternative fuels (e.g., liquid propane, hydrogen), since the agency has not issued any FMVSS applicable to other alt ernative fuels.

I hope you find this information helpful. If you have any other questions, please contact Marvin Shaw at this address or by phone at (202) 366-2992.

ID: nht87-3.41

TYPE: INTERPRETATION-NHTSA

DATE: 12/10/87

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Mercedes-Benz Truck Company, Inc.

TITLE: FMVSS INTERPRETATION

TEXT:

Mercedes-Benz Truck Company, Inc. 4747 N. Channel P.O. BOX 3849 Portland, Oregon 97208

Dear Mr. Rossow:

This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard No. 121, Air Brake Systems. Section 56.2.1 of that standard specifies for certain tests conducted on a dynamometer that "(the dynamometer inertia for each wheel is equivalent to the load an the wheel with the axle loaded to its gross axle weight rating." According to your letter, you have interpreted the term "equivalent" in this section to "authorize compliance testing by reference to axle loads under actual st opping conditions." You requested confirmation of this interpretation. As discussed below, we disagree with your suggested interpretation.

By way of background information, the National Highway Traffic Safety 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.

As indicated in your letter, your request for an interpretation was submitted in light of recent correspondence between your company and NHTSA's Office of Vehicle Safety Compliance (OVSC). OVSC requested you to submit information on the compliance with S tandard No. 121 of the Mercedes-Benz model L-1317, a two axle straight truck. You responded to that request by submitting a compliance certificate and interpretation concerning section 56.2.1. In letter dated April 9, 1987, OVSC informed you that it did not agree with your interpretation.

Standard No. 121's dynamometer tests are set forth in section S5.4. That section specifies that brake assemblies must meet the requirements of 55.4.1 (brake retardation force-relevant only to towed vehicles), 55.4.2 (brake power), and 55.4.3 (brake recov ery), under the conditions of 56.2. One of those conditions, set forth in 56.2.1, is as follows:

S6.2.1 The dynamometer inertia for each wheel is equivalent to the load on the wheel with the axle loaded to its gross axle weight rating. For a vehicle having additional gross axle weight ratings specified for operation at reduced speeds, the GAWR used is that specified for a speed of 50 mph, or, at the option of the manufacturer, any speed greater than 50 mph.

In support of your suggested interpretation, you noted that axle loads of a decelerating vehicle vary under different deceleration conditions, i.e., as a vehicle traveling forward decelerates, the load of the axles shifts so that the front axle load rise s and the rear axle load falls. You stated that it is your reading of Standard No. 121 that the manufacturer "can assess compliance by either using a static load value or determining which of the varying values of the axle load should be considered in vi ew of actual vehicle behavior." With respect to gross axle weight rating (GAWR), you suggested that when used in the context of Parts 567 and 568, the GAWR is properly measured in a static manner, to permit a static determination of whether the load carr ying capacity of a vehicle axle in actual use has been reached. For dynamometer tests of service brakes under dynamic conditions, however, you argued that such tests should properly take into account the dynamic effects of deceleration.

You then stated the following:

The language of 56.2.1, setting dynamic test conditions, indicates that the dynamometer inertia for each wheel is to be set at the "equivalent" to the load on the wheel, when the axle is loaded to its GAWR (i.e., its load-carrying capacity). This languag e is not restrictive and grants a manufacturer the flexibility of determining an "equivalent" loading in consideration of the dynamic phenomena in conducting the texts required by 55.4. Thus, the static GAWR is permitted to be linked to dynamic condition s by the word "equivalent."

We disagree with your suggested interpretation, which we believe is inconsistent with the language of S6.2.1, past interpretations of that provision, and the compliance test procedures the agency has long followed with respect to this provision. As indic ated above, 56.2.1 specifies that the dynamometer inertia for each wheel is "equivalent to the load on the wheel with the axle loaded to its gross axle weight rating." The phrase "equivalent to the load" uses the singular "load," instead of the plural "l oads," to show that the dynamometer inertia has only a single value. By itself, this suggests that 56.2.1 was not intended to provide multiple options for the dynamometer inertia setting, depending on the dynamic conditions simulated.

Further, the overall language of 56.2.1 shows how the single dynamometer inertia setting is to be determined. The term "GAWR" is defined in 49 CFR Part 571.3 as "the value specified by the vehicle manufacturer as the load-carrying capacity of a single ax le system, as measured at the tire-ground interfaces." When an axle is loaded to its load-carrying" capacity, there is one "load on the wheel," at whose "equivalent" the dynamometer inertia must be set.

While we believe that the language of section S6.2.1 is clear on the issue raised by your letter, we also note that agency guidance in the form of a past interpretation letter and OVSC's laboratory procedures for Standard No. 121 are also clear. In an in terpretation letter to Wagner Electric, dated May 26, 1972, the agency stated:

In the dynamometer test conditions of S6.2.1, the dynamometer inertia for each brake assembly is based on 1/2 the GAWR of the axle. The rating for each axle is required to be stated separately. If, in the example you give, you choose to give 17,000 pound s as the rating for each axle, then the dynamometer inertia would be at 8,500 pounds for each brake assembly.

That interpretation explicitly states that the dynamometer inertia is set with regard to the assigned GAWR, and makes no reference to the varying values of axle load during braking. This agency interpretation has been a matter of public record for the la st 15 years. Moreover, as OVSC noted in its letter of April 9, 1987, its test procedure TP-121-02 provides a specific formula for calculating "dynamometer inertia equivalent to the GAWR for the applicable vehicle axle." This test procedure has been used by the agency since March 163 1978, and has been available to the public since that date.

You asserted in your letter that the static GAWR is "permitted to be linked to dynamic conditions by the word 'equivalent'." We find no basis in the word "equivalent" for your suggestion that the load on the wheel- should somehow be calculated during bra king. Section S6.2.1 uses the term "equivalent" to account for the fact that the terms "load" and "inertia" are different without the same dimensions and are not numerically equal; an axle's tire rolling radius must be considered in determining the prope r inertia as well as the load. We note that section S5.4.2.1 of Standard No. 121 uses the term "equivalent" in the same manner. That section specifies for dynamometer testing that the drum or disc be "rotating at a speed equivalent to 50 m.p.h." Since t he drum or disc is obviously not moving along longitudinally, the word "equivalent" in that section is used to bridge the gap between longitudinal and rotational movement.

Your letter also argued that a February 18, 1976, interpretation letter to Oshkosh supports your suggested interpretation of 56.2.1. Oshkosh had asked whether a vehicle that meets section S5.1.1's requirements for air Compressor capacity when it is movin g must also comply when the vehicle is stationary. The agency stated:

Section S5.1.1 does not specify whether or not the vehicle is moving as a test condition for the requirement. In view of the absence of this test condition, the NHTSA will resolve differences in this test condition in the manufacturer's favor if they aff ect the outcome of testing.

We do not agree that this letter supports your suggested interpretation. The letter addressed only the issue of how a requirement should be read in view of the absence of a particular test condition. As explained at length above, we conclude that section S6.2.1 clearly specifies the particular test conditions to be followed for this section. Therefore, the Oshkosh letter is not relevant to requests for interpretation of S6.2.1.

You also argued that in order to provide an appropriate braking system, with proper distribution of brake forces between the axles, its design must take into account the transfer of weight from the rear axle to the front axle during normal and emergency braking conditions. You stated that such a design and compliance test leads to a significant reduction in premature lockup of the rear axle. You also argued that NHTSA has recognized your braking system as "a safe and effective system" in its research te sting.

We agree that a manufacturer must take into account the transfer of weight from the rear axle to the front axle when designing an appropriate braking system. This is necessary to provide safe brake performance during varying loading conditions, for norma l and emergency brake applications on varying road conditions: and it is so for all kinds of vehicles. However, the requirements of Standard No. 121 do not require vehicles to have too much rear braking, as you appear to imply. The requirements of S5.4.2 (Brake Power), and S5.4.3 (Brake Recovery), are minimum performance requirements intended to help ensure that brakes retain adequate stopping capacity during and after exposure to conditions caused by prolonged or severe use, such as long, downhill driv ing. In practice, in order to perform well in such conditions, both front and rear brakes must have a minimum capacity, and this capacity is related to GAWR despite the fact that the actual loads borne by the front and rear axles vary during different br ake applications. The agency therefore referred to GAWR in section 56.2.1, because this is an objective value that is readily ascertainable for every vehicle, and performance based on this value meets the particular safety need provided for by the requir ements of section S5.4. These minimum requirements are not intended, nor do they operate, as a restriction on the design decisions that manufacturers must make independently to distribute braking capacity to meet anticipated load distributions.

Contrary to your assertion, NHTSA has not concluded that your brake system is "safe and effective." We also note that the quotations of the agency's research report cited in your letter address only limited aspects of braking performance and are taken ou t of context. We note that you stated that "(t)he Agency reported finding that the subject vehicle's front and rear axles were '. . . well balanced and tended to lock at close to the same pedal effort level.' (p. 19)." A more complete quotation is as fol lows:

. . . In the empty driver best effort stops the driver was also able to utilize this peak friction, although not as effectively as the antilock, because the brakes on front and rear axles of the vehicle were well balanced and tended to lock at close to t he same pedal effort level. In the loaded case, however, the front axle tended to lock prematurely and it Has not possible for the driver to maintain all four wheels near the peak friction level. He could keep the front tires near the peak but when this occurred rear braking was relatively low. If he applied more braking, the front axle locked and he lost steering control due to lack of lateral traction at the front tires."

Based on the information before the agency, OVSC is continuing its investigation concerning the compliance of your vehicles with Standard No. 121.

Sincerely,

Erika Z. Jones Chief Counsel

May 22,1987

Ms. Erika Z. Jones, Chief Counsel Department of Transportation National Highway Traffic Safety Administration 400 Seventh Street, SW Washington, D.C. 20590

RE: Request for an Interpretation Concerning FMVSS 121, Air Brake Systems

Dear Ms. Jones:

On behalf of our parent company, Daimler-Benz Aktiengesellschaft (DBAG), Mercedes-Benz Truck Company, Inc. (MBTC) requests an interpretation of Federal Motor Vehicle Safety Standard (FMVSS) 121, Air Brake Systems. This standard specifies that for tests c onducted on a dynamometer, "The dynamometer inertia for each wheel is equivalent to the load on the wheel with the axle loaded to its gross axle weight rating.

49 C.F.R. S 571.121.56.2.1. DBAG has interpreted the term "equivalent in this regulation to authorize compliance testing by reference to axle loads under actual stopping conditions. It is this interpretation which we are asking be confirmed by your offic e.

The need for such an interpretation is the result of recent correspondence between MBTC and NHTSA. NHTSA's Office of Vehicle Safety Compliance has asked MBTC, as the manufacturer of trucks bearing the trade name of Mercedes-Benz, to submit information on the compliance with FMVSS 121 of Mercedes-Benz truck model L-1317. MBTC filed a response to this request containing the DBAG compliance certificate and the foregoing interpretation. In a letter dated April 9, 1987, NEF-31 HTS CIR 2879.1, the Office info rmed MBTC that it does not agree with the DBAG interpretation of FMVSS 121 used to assess compliance.

In determining compliance with FMVSS 121, DBAG recognizes, as do all automotive engineers, that axle loads of a decelerating vehicle vary under different deceleration conditions. That is, as a vehicle traveling forward decelerates, the load on the axles shifts so that the front axle load rises and the rear axle load falls. (See DBAG Compliance Certificate, section 2.16) Under Standard 121, the manufacturer must specify an axle load in connection with the tests conducted to assess compliance. It is DBAG' s reading of Standard 121 that the manufacturer can assess compliance by either using a static load value or determining which of the varying values of the axle load should be considered in view of actual vehicle behavior.

As noted above, Standard 121 refers to the "gross axle weight rating" (GAWR) of the vehicle. GAWR is defined generally as "the value specified by the vehicle manufacturer as the load-carrying capacity of a single axle system, as measured at the tire-grou nd interfaces."

49 C.F.R. S 571.3(b). When used in the context of Parts 567 (Certification) and 568 (Vehicles Manufactured in Two or More Stages), the GAWR is properly measured in a static manner, to permit a static determination of whether the load carrying capacity of a vehicle axle in actual use has been reached. The nominal GAWR value on the certification label therefore must be used for such a determination.

A test to represent a dynamic procedure such as braking presents quite different requirements. Instead of a static measurement, such a test should properly take into account the dynamic effects of deceleration. Standard 121 mandates dynamometer tests of service brakes under dynamic conditions. Thus, the question is whether the standard is specific in requiring a GAWR determined on a static test or whether language would permit the type of interpretation utilized by DBAG.

The language of 56.2.1, setting dynamic test conditions, indicates that the dynamometer inertia for each wheel is to be set at the "equivalent" to the load on the wheel, when the axle is loaded to its GAwR (i.e., its load-carrying capacity). This languag e is not restrictive and grants a manufacturer the flexibility of determining an "equivalent. loading in consideration of the dynamic phenomena in conducting the tests required by 55.4. Thus, the static GAWR is permitted to be linked to dynamic conditions by the word "equivalent."

The foregoing interpretation is supported by prior interpretative guidelines of the Agency. The standard itself does not specify that the "load on the wheel" must be evaluated in a static manner. In fact, it specifically uses the word "equivalent," a wor d not used in other sections of the standard. (See for comparison 5.5.6.1) In the context of braking, a manufacturer could, therefore, reasonably conclude that the dynamics of wheel loads under deceleration can be considered. In a letter to the Oshkosh T ruck Corporation, the Chief Counsel's Office has supported such an interpretation. In the Oshkosh case, the Agency indicated that, where the standard is silent as to an issue, the manufacturer may exercise its discretion. Oshkosh had asked whether a vehi cle that complies with S5.1.1 of the standard (air compressor capacity) when it is moving must also comply when the vehicle is stationary. The Chief Counsel replied:

"Section S5.1.1 does not specify whether or not the vehicle is moving as a test condition for the requirement. In view of the absence of this test condition, the NHTSA will resolve differences in this test condition in the manufacturer's favor if they af fect the outcome of testing." Letter from Richard B. Dyson to Oshkosh Truck Corporation (February 18, 1976).

For these reasons also, DBAG relies on the conclusion that Standard 121 does not specifically restrict the test procedure and permits a manufacturer to assess compliance by reference to the dynamics of braking for an actual vehicle. DBAG has concluded th at in order to provide an appropriate braking system, with proper distribution of brake forces between the axles, its design must take into account the transfer of weight from the rear axle to the front axle during normal and emergency braking conditions . Such a design and compliance test leads to a significant reduction in premature lockup of the rear axle.

The Agency's own testing of the L-1317 supports this Conclusion. In August 1986, the Agency issued a report entitled, "Performance Evaluation of a Production Antilock System Installed on a Two Axle Straight Truck (NHTSA's Heavy Duty Vehicle Brake Researc h Program Report #6)" which included dynamic testing of this vehicle with and without the use of its ABS system. The Agency reported finding that the subject vehicle's front and rear axles were "... well balanced and tended to lock at close to the same p edal effort level." (p. 19). Further, the Agency reported that "... in the empty condition the vehicle has a relatively high braking efficiency over a broad range of road friction levels." The report explains that efficiency is a measure of the vehicle's ability to use available friction before lockup and loss of control occurs (p. 19). Finally, the report generally notes "if loss of control of the overbraked axle prevents the driver, no matter how skilled he is, from utiliz ing the full capability of the underbraked axle .." (p. 22). Accordingly, not only does FMVSS 121 provide sufficient breadth to allow the interpretation utilized by Daimler-Benz, its use results in a braking system which the Agency has recognized as a sa fe and effective system.

Based on the foregoing request, we would appreciate your office responding with respect to the appropriateness of this interpretation. If you require any additional information, please do not hesitate to contact me.

Sincerely,

Gary W. Rossow Director, Government Technical Affairs

cc: Mr. George L. Parker

ID: nht94-4.53

TYPE: INTERPRETATION-NHTSA

DATE: October 14, 1994

FROM: Randal Busick -- President, Vehicle Science Corporation

TO: Mary Versailles, Esq. -- Office of the Chief Counsel, NHTSA

TITLE: Re: Request for interpretation of FMVSS 208 S7.1.2

ATTACHMT: Attached to 1/5/95 letter from Philip R. Recht to Randal Busick (A43; Std. 208; Std. 210)

TEXT: Dear Ms Versailles:

This is to request a clarification of FMVSS 208 S7.1.2. More specifically, would a seat belt system as shown on the attached drawing be in compliance with S7.1.2 as a so-called "semi-integrated" seat belt?

As shown on the drawing, the inboard lower FMVSS 210 anchorage, n1 is located on the seat frame and thus, as the seat moves fore and aft, the system allows a minimum of two seat belt adjustment positions and the distance between the two extreme adjustmen t positions of the system is more than 5 cm.

n1 The belt which holds the buckle is attached to this inboard anchorage.

We look forward to your response. If you have any questions, kindly contact the undersigned.

Sincerely

Enclosure

(Drawing omitted.)

ID: nht73-2.23

DATE: 03/26/73

FROM: Francis Armstrong; Francis Armstrong; Office of Standards Enforcement

TO: File

TITLE: FMVSS Interpretation

TEXT:

March 26, 1973 Close-out of Investigatory File, CIR 584 N41-21RGa; CIR 584 Director, Office of Standards Enforcement File The Investigatory File, CIR 584, has been closed out inasmuch as the manufacturer utilitzed a driver test dummy during his certification tests. This alternate certification technique is permissible by FMVSS No. 204. A maximum rearward dynamic horizontal displacement of 5.1 inches was obtained on the standards enforcement Checker test vehicle, NHTSA No. 71518, during a 29.3 mph frontal barrier impact. This maximum displacement was only 0.1 inch greater than the maximum allowable and which occurred late (124 msec.) during the collision interval. The manufacturer's submitted data indicated that their test dummy impacted the steering control early (approximately 55 msec.) in the vehicle impact phase and thereby would restrict the steering control rearward displacement. It is therefore, concluded that the NHTSA vehicle would have met the performance requirements of FMVSS No. 204 if the alternate driver dummy technique had been utilized in the test. Francis Armstrong

ID: nht88-3.6

TYPE: INTERPRETATION-NHTSA

DATE: 08/15/88

FROM: LEBOEUF LAMB LEIBY AND MACRAE

TO: KATHLEEN DEMETER -- ASSISTANT CHIEF COUNSEL FOR GENERAL LAW NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

TITLE: PORSCHE'S JUNE 28 REQUEST FOR REGULATORY INTERPRETATION FMVSS 101 AND 102

ATTACHMT: ATTACHED TO LETTER DATED 04/03/89 FROM ERIKA Z. JONES -- NHTSA TO KARL H. MAYER, REDBOOK A33 (4), STANDARD 101, STANDARD 102; CONFIDENTIAL LETTER DATED 06/28/88 FROM KARL H. MAYER TO ERIKA Z. JONES, REQUEST FOR INTERPRETATION -- CLARIFICATION F MVSS 101 AND FMVSS 102; LETTER DATED 06/28/88 FROM KARL H. MAYER TO ERIKA Z. JONES -- NHTSA, REQUEST FOR CONFIDENTIAL TREATMENT

TEXT: Dear Ms. DeMeter:

I write to confirm our conversation of August 15 concerning Porsche's June 28, 1988 request for a regulatory interpretation of FMVSS 101 and 102. We ask that the June 28 request and the attachments to that request remain confidential until September 30, 1988, at which time this information may be made public.

I understand from our conversation with NHTSA will honor our request to keep the information confidential until September 30. If my understanding is not accurate, please let me know.

Thank you for your cooperation.

Yours truly,