ID: nht74-2.6

DATE: 09/26/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Eagle International Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your July 16, 1974, request for approval of the Bendix "dual circuit air brake system" for use on your buses in satisfaction of Standard No. 121, Air brake systems. In a subsequent phone call with Mr. Herlihy of this office, you stated that your only concern was whether the standard requires a parking brake system that meets the axle-by-axle retardation force requirements of S5.6.1 and the grade holding requirements of S5.6.2.

The National Highway Traffic Safety Administration is unable to "approve" plans or prototype systems for compliance with a standard in advance, because there is no way to establish that a vehicle so equipped actually meets the requirements until it has been manufactured.

With regard to your specific question, S5.6 states that each vehicle shall have a parking brake system that meets the requirements of S5.6.1 or S5.6.2 at the manufacturer's option. This means that you are free to choose a system which meets either of these requirements but does not meet both.

Yours truly,

ATTACH.

July 16, 1974

Sid Williams; 400 7th Street, S.W.; Washington, D.C. 20024

Dear Sid:

Enclosed is a copy of our Dual Circuit Air Brake System as developed by the Bendix heavy vehicle system group (their drawing number SA-8117-99). With this is an explanatory writeup describing a circuit operation for normal running, parking position and for service brake failure on the rear or front axle.

We would appreciate receiving your comments and possibly your approval for use in compliance with safety standards #121.

As previously mentioned we would like to avoid the use of spring brakes especially on the tag axle because these wheels are independently sprung and have a tendency to lock up because they do not have a load dividing connection with the drive wheels.

I would appreciate your help on these matters and hope to hear from you soon.

With warmest personal regards,

Sincerely yours,

Harry L. Cuthbert -- Chief Engineer, Eagle International Inc.

Enc: 2

SA-9117-99

EXPLANATORY WRITE-UP

NORMAL RUNNING

1. All reservoirs charged and accessory pressure protection valve open.

2. Parking Control Valve handle in release position. DD-3 Valve (Item 20) does not deliver air. DD-3 locks are disengaged. Service Interlock Valve controlled from its delivery line.

3. "Stand-by" Valve (Item 15) does not deliver any brake valve air, and low pressure indicator switches are open.

4. Service brakes can be applied by treadle valve; primary section of the brake valve applies rear axle and secondary section of the brake valve applies front axle.

SECONDARY BRAKES

1. A service brake failure, which would result in a rear axle circuit reservoir pressure loss will cause the "Stand-by" Valve (Item 15) to open. This will supplement the front axle brakes with rear axle brakes by applying modulated from axle circuit service pressure to the parking diaphragm.

2. A front axle circuit service brake failure will only cause a loss of front axle braking. Full service brakes can be applied on the rear axle through the treadle valve (Item 14).

3. In event of a broken treadle, the parking brakes can be applied as a "Back-up" emergency.

PARKING POSITION

1. When Parking Control Valve Handle (Item 18) is moved to the "park" position, the DD3 locks engage. The parking DD3 Valve will first deliver adequate pressure to the DD3 parking diaphragm, and then exhaust it automatically. In this condition, the parking application will remain applied strictly by "a mechanical means."

2. Service Interlock Valve being decontrolled, is closed and parking brakes cannot be released until PP-1 is pushed and a full service application is made and released, in this sequence.

RCF: dw Current for Drawing Revision #7; 6/18/74 (Graphics omitted) ITEM QTY DESCRIPTION 1 1 AIR COMPRESSOR 2 1 GOVERNOR 3 1 RESERVOIR-SUPPLY 4 1 (Illeg.) 5 1 (Illeg.) 6 1 (Illeg.) 7 1 (Illeg.) 8 3 DRAIN COCK 9 1 SAFETY VALVE 10 1 PRESSURE PROTECTION VALVE 11 3 SINGLE CHECK VALVE 12 3 LOW PRESSURE SWITCH 13 2 AIR PRESSURE GAUGE 14 1 (Illeg.) 15 1 (Illeg.)

TWO-STEP RELEASE OF DD-3 ACTUATORS.

2. (Illegible Words)

3. (Illegible Words)

(Graphics omitted)

(Illeg. table)

ID: nht74-2.7

DATE: 07/24/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: The Bendix Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Bendix's June 10, 1974, request for interpretation of the Standard No. 121 requirement in S5.5.1 that "on a vehicle equipped with an antilock system, electrical failure of any part of the antilock system shall not increase the actuation and release times of the service brakes." You ask whether this language permits use of a separate device that senses electrical failure in the antilock system and automatically reduces pressure to the front brakes as a safety measure. The device would increase brake actuation and release time.

S5.5 is addressed to antilock systems and S5.5.1 mandates that antilock systems be designed not to interfere with air brake performance if they fail electrically. S5.5.1 does not prohibit separate safety devices which are designed to operate in the event of antilock electrical failure to compensate for that failure. Therefore the Bendix automatic front axle limiting system, as we understand its operation, is not prohibited by S5.5.1 simply because it operates when it senses an antilock electrical failure.

Sincerely,

ATTACH.

BENDIX HEAVY VEHICLE SYSTEMS GROUP

James B. Gregory -- Administrator, National Highway Traffic Safety Administration

June 10, 1974

Subject: Request for Interpretation

Re: S5.5.1 (Antilock System Failure) Federal Motor Vehicle Safety Standard No. 121

Gentlemen:

As a result of the adoption of the stopping distance provisions of FMVSS No. 121, higher torque brakes on front axles were required. On certain vehicles, these higher torque brakes created wheel lockup/stability problems which were to be solved or controlled by the use of an antilock system. The Automotive Industry concerns with vehicle stability, as expressed in petitions submitted to NHTSA, are directed towards antilock reliability and stability problems that may be amplified by an antilock system failure.

The concern with vehicle stability due to high torque front brakes are recognized by NHTSA in Docket 74-10, Notice 1, wherein a manual control for limiting front axle braking was proposed. Such proposal was, however, subsequently withdrawn in Docket 74-10, Notice 2, primarily, we suspect, because of the manual control feature.

The Bendix Corporation, Heavy Vehicle Systems Group, has developed an automatic front axle limiting system, separate from the antilock system itself, that will sense an electrical failure of the front axle antilock system and "automatically" reduce front axle braking to 50% of that normally provided. Attention is invited to the performance comparison (Enclosure 1) wherein the automatic limiting curve reflects that 120 psi rear axle pressure is required to reach 60 psi at the front axle. While Bendix' system does not introduce an air line restriction, it does limit the level of front axle braking pressures so that the 60 psi and 95 psi pressure levels set forth in Section 5.3.3 (Brake Actuation Time) and Section 5.3.4 (Brake Release Time) respectively, are not achieved, nor are the corresponding actuation and release times realized.

Section 5.5.1 (Antilock System Failure) provides that an ". . . electrical failure of any part of the antilock system shall not increase the actuation and release times of the service brakes." Bendix is of the opinion that since the affect on response time is caused by a system separate from the antilock system itself, it is not within the purview of, and hence not in conflict with Section 5.5.1.

An official interpretation is requested from NHTSA as to whether it concurs with Bendix' opinion that the Bendix Automatic Front Axle Limiting System is not covered by the provisions of, and is not in conflict with Section 5.5.1.

We would be happy to discuss the details of this matter if you feel additional information is necessary.

Very truly yours,

R. W. Hildebrandt -- Group Director of Engineering

Attachment

PERFORMANCE COMPARISON

Standard (Non Limiting) System Vs: System With Automatic Limiting Upon Antilock Failure

(Graphics omitted)

Rear Axle Brake Pressure (PSI)

ID: nht74-2.8

DATE: 11/06/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Truck Body and Equipment Association, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your October 3, 1974, questions whether the exemption for 24,000-pound axle vehicles from Standard No. 121, Air brake systems, until September 1, 1976, applies to fire fighting vehicles, and whether a tandem axle assembly consits of two "axle systems" for purposes of our definition of "Gross axle weight rating."

The answer to both of your questions is yes. A fire fighting vehicle would qualify for exemption until 1976 if any of its axles has a gross axle weight rating of 24,000 pounds or more.

A tandem axle assembly, which we understand to mean a running rear assembly consisting of two axles and associated components, comprises two "axle systems." As we pointed out in the preamble to Notice 2 of Docket No. 74-10, the term "axle system" is used only to avoid confusion in situations where a suspension system does not employ an axle (39 FR 17550, May 17, 1974).

Yours truly,

ATTACH.

TRUCK BODY AND EQUIPMENT ASSOCIATION, (Illegible Word)

October 3, 1974

Richard Dyson -- Office of Chief Council, National Highway Traffic Safety Administration

Dear Mr. Dyson:

Recently several members of our Fire Apparatus Manufacturers Division have contacted us with questions concerning FMVSS 121 and its effective date. In order that we may accurately answer these questions, we would like the following clarified.

(1) Does a fire apparatus qualify for the "Special Permit Vehicle" classification if it is equipped with an axle with a GAWR equal to or greater than twenty-four thousand pounds (24,000 lbs.)?

(2) Is a tandem axle assembly comprised of two "Axle Systems", per your GAWR definition?

Your cooperation in this matter is greatly appreciated.

Sincerely yours,

Byron Crampton -- Manager of Engineering Services

ID: nht74-2.9

DATE: 03/19/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: American Snowblast Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your March 4, 1974, question whether your rotary snowplows, constructed with four-wheel drive and four-wheel steer and a top speed of 35 miles per hour, must be certified to conform to Federal motor vehicle safety standards. You also asked whether "certified brakes" will be sufficient certification to Standard 121, what the effects of a locked transfer case are on an anti-lock system, and what procedure exists to petition for an exemption from the standard.

I have enclosed an information sheet which explains that the vehicles you build for highway use are motor vehicles subject to the standard. The standard applies to the performance of the vehicle as a whole, not just to the brake system. In the event that the vehicles as completed do not actually comply, it is the manufacturer of the vehicle who is responsible.

I have enclosed a copy of the law and regulations explaining the basis for and necessary procedures to apply for a temporary exemption from our safety standards.

With regard to a locked transfer case, S6.1.11 of the air brake standard requires:

S6.1.11 Special drive conditions. A vehicle equipped with an interlocking axle system or a front wheel drive system that is engaged and disengaged by the driver is tested with the system disengaged.

Yours truly,

ATTACH.

March 4, 1974

Department of Transportation - NHTSA

Attention: Sid Williams

Gentlemen:

Please give us your opinion on where we stand with respect to FMVSS-121.

We build large rotary snowplows (brochure enclosed) which are sold primarily to airports. We do build an average of five or so per year for highway plowing, and this is our area of concern.

These machines are air braked, four wheel drive and four wheel steer, have a top speed of 35 m.p.h., and weigh less than 40,000 lbs. but more than 30,000 lbs.

Our questions are: must we certify; will certified brakes be sufficient to certify the vehicle; what are the effects of a locked transfer case on anti-lock; the procedure for petitioning for an exemption, etc.

Sincerely

AMERICAN SNOWBLAST CORPORATION;

D. L. Massy -- Chief Engineer

Enclosure Omitted.

ID: nht74-3.1

DATE: 07/30/74

FROM: RICHARD B. DYSON -- NHTSA ACTING CHIEF COUNSEL

TO: P. K. KAMATH -- SENIOR SAFETY ENGINEER OSHKOSH TRUCK CORPORATION

TITLE: N40-30 [ZTV]

ATTACHMT: LETTER DATED 07/09/74 FROM P.K. KAMATH TO RICHARD DYSON -- NHTSA, 49CFR PART 571 FMVSS 101; CONTROL LOCATION, IDENTIFICATION AND ILLUMINATION

TEXT: Dear Mr. Kamath:

This is in reply to your letter of July 9, 1974, asking whether Standard No. 101 requires identification and illumination of an emergency engine stop control, in addition to the engine stop control intended for normal use.

The "engine stop" control referred to in Standard No. 101 means any control used to stop the engine, and would include the emergency control. If it is important for the normal control to be identified and illuminated, it is all the more important that a control intended for emergency use meet the requirements of the standard. Identification such as "emergency engine stop" would be acceptable under Standard No. 101. Illumination, of course, must meet the requirements of the standard, but since you have not described the emergency system or its location we cannot offer a more precise comment.

Yours truly,

ID: nht74-3.10

DATE: 01/08/74

FROM: RICHARD B. DYSON -- NHTSA ASSISTANT CHIEF COUNSEL

TO: DARROLL P. YOUNG -- PRESIDENT YOUNG'S MACHINE CO. MONTICELLO, UTAH 84535

TITLE: N40-30 (TWH)

ATTACHMT: LETTER DATED 12/26/73 FROM DARRELL P. YOUNG -- PRESIDENT YOUNG'S MACHINE COMPANY TO THE OFFICE OF CHIEF COUNSEL NHTSA U.S. DEPARTMENT OF TRANSPORTATION

TEXT: Dear Mr. Young:

In place of the two standards which you requested in your letter of December 26, 1973, I am providing the following discussion of what vehicles qualify as "motor vehicles" subject to our regulations. If your vehicles are not "motor vehicles" under this definition, they are not required to conform to Standards 105a and 121. Section 102(3) of the Act defines motor vehicle as:

any vehicle driven or drawn by mechanical power manufactured primarily for use on the public streets, roads, and highways, except any vehicle operated exclusively on a rail or rails.

Thus, a motor vehicle is a vehicle which the manufacturer expects will use public highways as part of its intended function.

Tracked and other vehicles incapable of highway travel are not motor vehicles. Agricultural equipment is another non-motor vehicle category, because Congress clearly did not intend to include them in its coverage. In addition, vehicles intended and sold solely for off-road use (e.g. aircraft runway vehicles and underground mining vehicles) are not considered vehicles even if operationally capable of highway travel. They would, however, be considered motor vehicles if the manufacturer knew that a substantial proportion of his customers actually would use them on the highway.

Just as clearly, vehicles which use the highway on a necessary and recurring basis to move between work sites are motor vehicles. The primary function of some vehicles is of a mobile, work-performing nature and as such their manufacturer contemplates a primary use of the highway. Mobile cranes, mobile drill rigs, and towed equipment such as brush chippers and pull-type street sweepers are examples in this area. Even if the equipment uses highways infrequently, it is considered a motor vehicle on the same basis as is a "mobile structure trailer" which is often towed only once from the factory to the home site. All these motor vehicles qualify as trucks or trailers. As such they are subject to several of the motor vehicle safety standards, and their manufacturer must comply with other regulations in Chapter V of Title 49, Code of Federal Regulations.

There are some vehicles which are excepted from the motor vehicle classification despite their use of the highway. Highway maintenance and construction equipment such as lane stripers, self-propelled asphalt pavers, and other vehicles whose maximum speed does not exceed 20 miles per hour and whose abnormal configuration distinguishes them from the traffic flow are not considered motor vehicles.

From these guidelines you should be able to determine whether your equipment qualifies as a motor vehicle, and if so, as a truck or a trailer. Please write again if you are unable to make this determination. I have enclosed an information sheet that advises you how to obtain an up-to-date copy of the regulations which apply to motor vehicles and their manufacturers.

ENCLOSURE

Yours truly,

ID: nht74-3.11

DATE: 06/28/74

FROM: AUTHOR UNAVAILABLE; Lawrence R. Schneider; NHTSA

TO: Volkswagen of America, Inc.

COPYEE: ING. Hans-Jurgen Sassor -- AUDI NSU Auto Union Germany

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your May 22, 1974, question whether Volkswagen's passive belt system may be equipped with a "comfort clip," and whether an optional Type I lap belt may be offered in conjunction with the passive system. Your passive system consists of an upper torso restraint and, in place of a lap belt, knee padding under the dashboard.

A vehicle which satisfies Standard No. 208, Occupant crash protection, may be equipped, at the option of the manufacturer, with additional safety belts which conform to Standard No. 209, Seat belt assemblies. Additional belts, like any required belt, must conform to the S7.2 requirements for latch mechanisms.

S7.2 Latch mechanism. A seat belt assembly installed in a passenger car shall have a latch mechanism --

(a) Whose components are accessible to a seated occupant in both the stowed and operational positions;

(b) That releases both the upper torso restraint and the lap belt simultaneously, if the assembly has a lap belt and an upper torso restraint that require unlatching for release of the occupant; and

(c) That releases at a single point by a push-button action.

This requirement assures that the occupant crash protection provided under Standard No. 208 is not diminished by a complicated and slow series of belt latch mechanisms which could otherwise be introduced into the vehicle.

Volkswagens' passive upper torso restraint and a separate active lap belt do not violate S7.2(b) in combination. Simultaneous release is required only "if the assembly has a lap belt and an upper torso restraint that require unlatching for release of the occupant." As described, Volkswagen's upper torso restraint does not require unlatching for release of the occupant.

With regard to our regulation of "comfort clips", we approved the use of a clip in a March 9, 1973, letter to General Motors, to relieve belt tension in limited circumstances. A copy of that letter is enclosed. In that case, the lap belt provided could be independently and firmly adjusted to limit occupant movement, providing protection in the event of lateral and rollover crashes. Until we have further details on the functioning of the Volkswagen clips, however, which we urge you to submit, we are unable to determine whether it would conform to the adjustment requirements of S7.1.1 of Standard No. 208, Occupant crash protection.

May 22, 1974

Lawrence R. Schneider Chief Counsel National Highway Traffic Safety Administration

Subject: MVSS 208, Occupant Protection - Request for Clarification

With the publication of Docket 74-4, Notice 2 (39 FR 14593), Volkswagen believes that MVSS 208 now adequately addresses the basic requirements covering passive belt systems, such as the Volkswagen passive shoulder belt/knee bolster restraint described in our petition of October 1, 1973.

However, in the final development phase of our passive belt system the possible inclusion of two ancillary devices came under consideration:

(1) the addition of an active lap belt,

(2) the addition of a "comfort clip" to the passive shoulder belt to relieve the belt force against the occupant during non-impact conditions.

Volkswagen respectfully requests NHTSA clarification of the current Federal requirements covering each of these items, which are discussed in more detail below.

1. Additional Active Lap Belt

Here we are interested in the requirements for the installation of active lap belts together with passive restraints, where the requirements of MVSS 208 are met by the passive restraints alone.

To our knowledge, the last published NHTSA statement addressing this matter appeared in 35 FR 16928 (Preamble to Docket 69-7, Notice 7): "Under the standard as adopted manufacturers will be free to supply seat belts as optional or standard equipment, but may not use them to satisfy the requirements of the standard. Standard No. 210 will continue to require seat belt anchorages to be installed by manufacturers, so that persons who wish to have seat belts installed in their vehicles, for their own use or for use with child seating systems, will be able to do so."

Specifically, we would like to know if a Type 1 lap belt (conforming to MVSS 209) can be installed in addition to the Volkswagen passive shoulder belt/knee bolster system, under either of the following circumstances:

a) where a vehicle equipped with the passive belt system alone meets the requirements of S4.1.2.2 and S4.5.3 of MVSS 208 (second option for passenger cars manufactured from Sept. 1, 1973 to the time when this option expires);

b) where a vehicle equipped with the passive belt system alone meets the requirements of S4.1.3 (a) through (d) (1) proposed in Docket 74-14, Notice 1, and S4.5.3 of MVSS 208.

Our main area of concern in this matter is in regard to the latch mechanism. The passive shoulder belt would have a latch mechanism conforming to S7.2 of MVSS 208, as required under S4.5.3.3(a). If the active lap belt is not governed by MVSS 208, the application of S7.2(b) of MVSS 208 for simultaneous release of lap and upper torso restraint is questionable.

2. Addition of "Comfort Clip"

We are aware that certain vehicles equipped with upper torso restraints with emergency-locking retractors incorporate belt force relief devices ("comfort clips") to make wearing of the belt more comfortable. Although the specifications governing these devices have not been incorporated into the Safety Standards, we understand that correspondence between individual manufacturers and the NHTSA has addressed the guidelines for their use. Since such a "comfort clip" could be applied to the VW passive belt, NHTSA clarification of the regulations relating to this specific usage is requested.

Your early attention to these inquiries would be greatly appreciated, in view of the lead-time constraints we would be facing for possible incorporation of the described items in 1975 model vehicles.

J. W. Kennebeck

Manager

Emissions, Safety & Development

ID: nht74-3.12

DATE: 09/27/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: The Fairmount Press

TITLE: FMVSR INTERPRETATION

TEXT: This is in response to your letter of August 19, 1974, inquiring as to the compliance of your MVF odometer disclosure form with the Federal odometer requirements.

The MVF form enclosed in your letter fails to comply with our regulation in several respects. The statement referring to the mileage indicated on the odometer at the time of the vehicle's transfer must be phrased to indicate that the disclosure document was executed at the moment of the vehicle's transfer, not at some later time. In addition, the statement must be written in such a manner that it is clear it is to be completed by the transferor alone. To satisfy these criteria the statement should read

"I, , state that the odometer mileage indicated on the vehicle described above, at the time of transfer to , is as follows:"

Instructions are necessary on your form to ensure that the section specified for the disclosure of mileage is completed in a consistent manner by all persons. This can be accomplished by inserting the following statement above the lines provided for stating the vehicle's mileage:

"(Complete line 1; and where applicable, complete line 2 and check line 3.)"

We urge you to reprint your disclosure forms to reflect the changes suggested above as they are not currently in compliance with Federal odometer requirements.

Your Interest is appreciated.

Yours Truly,

THE FAIRMOUNT PRESS

August 19, 1974

Richard B. Dyson

Ass't. Chief Counsel

NHTSA

Enclosed please find previously approved copies of our MVF form. They were approved on June 11, 1973.

We have been informed by one of our customers that there have been changes made. The customer was unaware of what changes had been made, but was advised by another New Car Dealer that indeed changes had been made.

We would appreciate your rechecking the forms enclosed and ascertaining if they are still in compliance with current regulations.

A prompt reply would be appreciated in that we are preparing for a new run of the MVF forms, and if there are any changes, we wish to include same.

Thank you for your cooperation and help in this matter.

Norman E. Salzman

General Manager

ODOMETER MILEAGE STATEMENT

Required Under Section 408, P.L. 92-573 USA Also Pursuant to Sect. 392-E, General Business Law, State of New York

Date of this Statement

Year Make Model

Body Type Color/s

Vehicle Ident. No.

No. Cylinders Last Plate No.

State Year

The mileage appearing on the odometer of the motor vehicle described above at time of transfer to:

was as follows:

1. miles

2. Total Cumulative Miles (If over 100,000)

3. [] The actual mileage differs from the odometer reading for reasons other than odometer calibration, error and that the actual or true mileage is unknown.

Seller's Name

Seller's Address

Seller's Signature

(Federal regulations require you to state the odometer mileage upon transfer of ownership. An inaccurate statement may make you, liable for damages to your transferee, pursuant to Section 409(a) of the Motor Vehicle Information and Cost Savings Act of 1972, Public Law 92-513.)

I/We (Transferee) hereby certify that I/We have received a copy of the above odometer mileage statement.

ID: nht74-3.13

DATE: 01/03/74

FROM: AUTHOR UNAVAILABLE; Lawrence R. Schneider; NHTSA

TO: General Motors Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of December 3, 1973, requesting clarification of paragraph S5.1(c) of Motor Vehicle Safety Standard No. 217, "Bus Window Retention and Release." Your letter, and attached photograph of a push-out window, suggest that the words "window frame" in S5.1(c) refer not to the window "sash", the structure immediately surrounding the glazing material, but to the side of the bus.

We do not agree. The words "window frame" in S5.1(c), with respect to the push-out window, refer to the component that interfaces with the glazing.

The intent of S5.1 is to require a window retention system to be strong enough to retain occupants in a crash, at least up to the strength limit of the glazing itself. Since there are no limits on movement of the window "sash" relative to the bus structure, the interpretation you suggest would allow a window system that provides no retentive properties at all, thus defeating one of the main purposes of the standard.

ID: nht74-3.14

DATE: 06/11/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: The Adams & Westlake Company

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of April 16, 1974, concerning an interpretation of the requirements of Motor Vehicle Safety Standard No. 217, "Bus Window Retention and Release" (49 CFR 571.217). You appear to ask whether bus windows containing tempered glass must meet the release requirements of paragraph S5.3.2 after (as well as before) the retention test required by S5.1 when the glass breaks during the retention test. You state that tempered glass, once broken, is easily removed from the entire lite by touch, implying that when this is the case there is no longer a need for any release mechanism to be further tested.

Paragraph S5.3.2 requires the release mechanism to meet specified requirements both before and after the window retention test of S5.1 irrespective of the glazing material used in the lite. Consequently, release mechanisms for windows of tempered glass must conform to the requirements even though the glass may be broken during the retention test

While your argument that the requirement seems unnecessary when tempered glass is used is not without some basis, it is also quite likely, in our view, that bus passengers in a crash may be ignorant of the quality of tempered glass to which you refer and thus still attempt to operate the emergency exit using its release mechanism.

Yours truly,

April 16, 1974 Larry Schneider Office of Chief Consul National Highway Traffic Safety Administration

In regards to Motor Vehicle Safety Standard No. 217, "Bus Window Retention and Release", please refer to S5.3.2 which states:

"When tested under the conditions of S6. both before and after, the window retention test required by S5.1, each emergency exit shall allow manual release of the exit by a single occupant using force applications each of which conforms, at the option of the manufacturer either to (a) or (b)"

In the design of our particular application, we use a single sliding lite in a vehicle less than 10,000 lbs. GVWR and have opted to meet the low force application described in (a). See attached drawing DM-8991-2.

Our question centers on the above quote from the specification particularly when tempered glass is used. We foresee no difficulty in meeting the release test before the retention test but does the tempered glass, once broken, qualify as an uncostructed opening due to the ease of removal of any glass that might remain in the opening. Tempered glass as you are probably well aware, once stressed to the point of breakage, crumbles into small cubes over the entire lite and may be easily removed by touch.

Your earliest reply will be appreciated.

Ronald J. Hansing Project Engineer

Attachment cc: H. C. Gildnor

C. M. Miller

R. Prey

E. V. Gordon

July 10, 1974

Office of Chief Consul National Highway Traffic Safety Administration

ATTN: Richard Dyson

Please find enclosed drawing DK-1553 which should have been sent with letter dated July 3, 1974.

Ronald J. Hansing Project Engineer

RJH:cpp Enclosure