ID: 77-4.37

TYPE: INTERPRETATION-NHTSA

DATE: 11/15/77

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

TO: Wagner Electric Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Wagner Electric Corporation's October 26, 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 an interpretation that addresses this question, stating that a two-valve sequential release is permissible under S5.6.4.

SINCERELY, This responds to your April 23, 1974, question whether Standard No. 121, Air brake systems, is a proposal, whether buses manufactured after January 1, 1975, must conform to Standard No. 121 under all circumstances, what "cut-off date" exists for determination of brake equipment suppliers' ability to provide 121 components on time, and to what extent a bus must be completed to be certified as in compliance with applicable motor vehicle safety standards.

Standard No. 121 has been a final rule since February 27, 1971, and had an effective date of January 1, 1973. In 1972 the effective date was postponed until September 1, 1974. Recently the NHTSA further delayed the effective date for trucks and buses until March 1, 1975, having concluded that suppliers will be able to supply all necessary components by that date.

All buses manufactured after the effective date of an applicable standard must comply with its requirements, under @ 108(a)(1) of the National Traffic and Motor Vehicle Safety Act of 1966 (13 U.S.C. @ 1392(a)(1)), which states "No person shall . . . manufacture for sale . . . any motor vehicle . . . on or after the date any applicable Federal motor vehicle safety standard takes effect . . . unless it is in conformity with such standard. . . ."

You asked whether a trailer which is substantially complete before the effective date but lacks one or more parts due to parts shortages can be certified as conforming although it is equipped with a pre-121 brake system. By analogy with the rules allowing manufacturers to omit "readily attachable" items to be added later in the chain of distribution (Import regulations @ 12.80, Parts 567, 568), the NHTSA will accept a good-faith determination that a vehicle is substantially completed, where only a few parts subject to shortages are missing.

I would also like to answer a technical question raised by R. E. Houser of your engineering staff. In an April 23, 1974, letter he asked for an interpretation of the S5.6.4 language "The parking brake control shall be separate from the service brake control." as it applies to the DD-3 two-step brake release. The S5.6.4 requirement for a separate parking brake control is intended to address the actuation of the brake. We interpret this language not to prohibit the use of a two-step release involving a manual and a foot control.

WAGNER ELECTRIC CORPORATION

October 26, 1977

Office of Chief Counsel National Highway Traffic Safety Administration U.S. Department of Transportation

Re: Request for Interpretation of Section 5.6.4 of FMVSS-121

Section 5.6.4 of FMVSS-121 establishes the need for a parking brake control on a truck or bus to control the parking brakes on the vehicle and of any air braked vehicle that it is designed to tow. This section is reproduced below for your immediate reference.

Section 5.6.4 S5.6.4 Parking brake control trucks and buses. The parking brake control shall be separated from the service brake control. It shall be operable by a person seated in the normal driving position. The control shall be identified in a manner that specifies the method of control operation. The parking brake control shall control the parking brakes of the vehicle and of any air braked vehicle that it is designed to tow.

We request an interpretation which conforms that Section 5.6.4 does not preclude the sequential operation of two valves to release the parking brakes on the towed vehicle.

We have concluded that multiple valve operation is permissible to release the parking brakes on the towed vehicle. Our conclusion is based on the following observations:

1. A towing vehicle has historically been equipped with a separate trailer air supply valve to permit closure of the lines leading to the trailer when the vehicle is operated without an attached trailer. The ability of the parking brake control mentioned in Section 5.6.4 to establish air flow to the trailer is, therefore, dependent upon the operational position of the trailer air supply valve. An adverse interpretation of Section 5.6.4 would, therefore, eliminate the use of this simple disconnect feature and impose a design restriction which apparently was not intended.

2. Section 6.1.14 of FMVSS-121 defines the venting of the lines leading to the trailer when testing the towing vehicle emergency brake system per Section 5.7.3(a). The venting of the trailer supply line could appreciably reduce the pressure available on the towing vehicle to effect the emergency stop. Many vehicle manufacturers have elected to use a trailer air supply valve, which, under these conditions, will automatically trip to the closed position to preserve a high pressure in the tractor service brake resorvoir system.

These tripping air supply valves respond in a similar manner when the parking brake control required by Section 5.6.4 is utilized to park the combination vehicle. It is, therefore, necessary to manually restore the trailer air supply valve to the depressed position before air flow to the towed vehicle can be restored. An adverse interpretation of Section 5.6.4 would prohibit the use of these systems.

3. A clarification proposed in Docket 75-16 Notice 4 defines the desired interaction of the various push-pull valves provided on a tractor to control the tractor parking brakes and the flow of air to the trailer. We refer you specifically to Section 5.6.1(c)(1) and Section 5.8.1.2, which are reproduced below for your convenience.

Section 5.8.1.2

S5.8.1.2 Truck-tractor service brake system-criditional requirements. The service brake system of a truck designed to tow an air-brake-equipped vehicle shall, under the conditions of S6.1.15, be capable of modulating the air pressure in the control line of the control trailer by means of the service brake control. The service brake system shall be equipped with a means of opening and closing the connections from the service brake system of the towing vehicle to the supply and control lines of the control trailer, and simultaneously to open and close a vent to the atmosphere in the supply line to the control trailer. This means shall close automatically in all cases before automatic application of the parking brake system occurs, and before air pressure in all reservoirs of the truck service brake system drops to a level chosen at the option of the top manufacturer that is more than 20 psi, but less than 45 psi. This means shall also operate by utilization of a manual control that does not override automatic operations consisting of a red octagonal knob that, when pulled, closes the air supply to the towed vehicle and vents the trailer supply line to the atmosphere, and when pushed, opens the air supply line to a towed vehicle and permits presentation of the trailer supply (Illegible Word). The following legend shall appear on, above, or below the knob in block capital letters at least one-eighth of an inch in height:

TRAILER AIR SUPPLY

FUEL TO (Illegible Words)

Section 5.6.1.6(c)(1)

(c) In the case of a truck designed to tow an air-brake-equipped vehicle, be equipped with two parking brake system controls that meet the requirements of (1) and (2):

(1) The tractor and trailer parking control shall consist of a yellow diamond-shaped knob that, when pulled, applies the parking brake system of the towing vehicle and vents the trailer supply line to the atmosphere, and, when pushed, releases the parking brake system of the towing vehicle and permits pressurization of the trailer supply line. The following legend shall appear on, above, or below the knob in block capital letters at least one-eighth of an inch in height:

TRACTOR-TRAILER PARK PULL TO APPLY PUSH TO RELEASE:

Note in Section 5.6.1.6(c) that the tractor trailer park valve when pushed releases the tractor parking brakes and "permits pressurization of the trailer supply line". In Section 5.8.1.2, the trailer air supply valve when pushed opens the air supply line to a towed vehicle and "permits pressurization of the trailer supply line". The term "permits" accurately describes the present interaction of the two valves in question. The tractor trailer park valve cannot pressurize the trailer air supply line unless the trailer air supply valve is positioned to deliver air to the trailer supply line. Similarly, the trailer air supply valve cannot pressurize the trailer air supply line if previously vented by the tractor trailer park valve. The driver must restore the particular valve(s) to the appropriate delivery position to effect repressurization of the trailer air supply line. The sequence of valve restoration is dependent on the type of tractor protection system provided on the vehicle.

In conclusion, the apparent intent of the present Section 5.6.4 of FMVSS-121 is to insure the provision of a single (common) control means to apply the parking brakes on all of the vehicles in the combination and does not preclude the sequential operation of two valves to release the parking brakes on the towed vehicle. Interpretation of Section 5.6.4, which confirms this intent, will clarify this matter.

John W. Kourik, Chief Engineer Brake Products

ID: 005493drn

Mr. D. R. Smith
American Tire Distributors
12200 Herbert Wayne Court
Suite 150
P.O. Box 3145
Huntersville, NC 28070-3145

Dear Mr. Smith:

This responds to your July 14, 2003, request for information whether Federal Motor Vehicle Safety Standard (FMVSS) No. 211, Wheel Nuts, Wheel Discs, and Hub Caps is still in effect. The answer is no.

In a Federal Register notice of May 6, 1996, (61 FR 20172, copy enclosed) the National Highway Traffic Safety Administration rescinded FMVSS No. 211. The rescission took effect on June 5, 1996.

I hope this information is helpful. If you have any further questions, please feel free to contact Dorothy Nakama of my staff at this address or at (202) 366-2992.

Sincerely,

Jacqueline Glassman
Chief Counsel

Enclosure
ref:221
d.8/30/03

ID: nht93-9.15

DATE: December 15, 1993

FROM: Ted H. Richardson -- Fleet Coordinator, Priefert Manufacturing Company, Inc.

TO: Office of Chief Counsel, NHTSA (National Highway Traffic Safety Division)

TITLE: None

ATTACHMT: Attached to letter dated 4/12/94 from John Womack to Ted H. Richardson (A42; Std. 120; VSA 102(3))

TEXT:

Please forward opinion on "FMVSS No. 120" concerning new trailers with used tires. Per a conversation that I had with Mr. Walter Myers on 12/13/93, he felt that with the description of our product (over the phone) it would not apply. I am enclosing a product catalog that contains pictures and descriptions of the two pieces of equipment in question. I also request a copy of your definition of a trailer and a copy of FMVSS #120.

Thank you and please handle as expeditiously as possible.

ID: aiam4746

"Dear Mr. Bird: This responds to your request for an interpretation b this office as to whether a portable back massage device capable of being used in an automobile and powered by the vehicle's electrical system constitutes a piece of motor vehicle equipment as that term is used in the National Traffic and Motor Vehicle Safety Act of 1966 (the Act). I regret the delay in responding to your inquiry. The product you described in your letter consists of an inflatable cushion that conforms to the user's back and contains two electric massage units capable of massaging the upper and lower portions of the user's back. The device can also provide heat. It is designed for use either indoors or in a vehicle by means of an adapter which plugs into the cigarette lighter. When the device is used in a vehicle, it is simply placed on the seat, and does not require any additional installation, other than connection to a power supply. You have asked three questions about this device, which I have discussed below. Your first question was whether this device would be considered an item of 'motor vehicle equipment' within the meaning of the National Traffic and Motor Vehicle Safety Act? Section 102(4) of the Act (15 U.S.C. 1391(4)) defines, in part, the term 'motor vehicle equipment' as: any system, part, or component of a motor vehicle as originally manufactured or any similar part or component manufactured or sold for replacement or improvement of such system, part, or component or as any accessory, or addition to the motor vehicle..... (Emphasis added.) Since the portable back massage device is not original equipment or sold for replacment or improvement of any original equipment, it would be included within this definition only if it were an 'accessory.' In determining whether an item of equipment is considered an 'accessory,' the agency considers the following two criteria: First, when a substantial portion of the expected uses of a product are related to the operation or maintenance of motor vehicles, the product should be considered an item of motor vehicle equipment within the meaning of the Safety Act. Second, if the product is intended to be used principally by ordinary users of such motor vehicles, we would consider it to be an accessory. Based on the limited information you have provided, I am unable to reach a conclusion as to whether the back massage device would be considered an item of motor vehicle equipment. However, I will explain the considerations the agency focuses upon when applying the above critieria to specific products. We would determine the expected uses of a product by considering the product advertising, product labeling, and the type of store which retails the product, as well as any available information about the actual use of the product. We anticipate that products found to satisfy the first criterion will ordinarily, although not necessarily, be ones that are carried in a vehicle. For example, if the device is portrayed in advertising as being in used in motor vehicles, includes as a standard feature a 12 volt adapter enabling its use in a vehicle, and is sold through retail outlets specializing in automotive equipment and accesories, it would be more likely to be considered an item of motor vehicle equipment than a product which did not have these characteris- tics. In evaluating the second criteria, the agency looks at whether the product is intended primarily for the use of consumers, rather than by professionals such as automotive repair and service personnel. Your second question concerned whether the back massager would be subject to the Federal Motor Vehicle Safety Standards (FMVSS). If the device is not determined to be an item of motor vehicle equipment, it is beyond the scope of the agency's authority to regulate it. Even if it is determined to be motor vehicle equipment, and therefore subject to other provisions of the Safety Act, there is no Standard applicable to this type of device. With regard to your final question, we do not generally provide advice about the authority of other Federal agencies. However, if it is not considered motor vehicle equipment under the Safety Act, the Consumer Product Safety Commission may have requirements governing such a device. It is also possible the Food and Drug Administration might consider it to be a medical device subject to that agency's regulation. In addition, some States may choose to regulate such devices. I am enclosing an information sheet which describes the Federal Motor Vehicle Safety Standards program, and how to get copies of the standards and any other NHTSA regulation. If you have further questions, please contact this office. Sincerely, Stephen P. Wood Acting Chief Counsel Enclosure";

ID: aiam5209

"Dear Mr. Moore: This responds to your letter addressed to Walter Myer of this office in which you asked whether 15-passenger vans used by Linfield College to transport high school-age students to the college must comply with the Federal motor vehicle safety standards applicable to school buses. You explained in your letter and its enclosure that Linfield College sponsors an 'Upward Bound' program, in which selected high school-age students from disadvantaged families are transported to the college campus for academic tutoring and other activities, including field trips, counseling, etc. You have been advised that the college's 15-passenger vans 'may have to meet federal requirements in order to be leased or purchased from an automobile dealer.' Let me begin by stating that the National Highway Traffic Safety Administration's (NHTSA's) requirements for new school buses regulate the manufacture and sale or lease of new vehicles used for transporting students. The Federal requirements do not, however, regulate what bus may be used for particular student transportation purposes. The requirements that apply to the use of school vehicles are set by the State. Thus, if there are regulations about what buses an Oregon college must use to transport Oregon high school students, such regulations are administered by the State of Oregon, not the Federal government. Some background information on our requirements might be helpful to your inquiry. The National Traffic and Motor Vehicle Safety Act, 15 U.S.C. 1381 to 1431, as amended (Safety Act) authorizes NHTSA to issue Federal motor vehicle safety standards (FMVSSs) applicable to the manufacture and sale of new motor vehicles, including school buses. The Safety Act defines a school bus as 'a passenger motor vehicle which is designed to carry more than 10 passengers in addition to the driver, and which . . . is likely to be significantly used for the purpose of transporting primary, preprimary, or secondary school students to or from such schools or events related to such schools.' It is a violation of the Safety Act for any person to sell or lease any new motor vehicle as a school bus that does not comply with all Federal school bus safety standards. It is not a violation of Federal law, however, to sell any noncomplying used vehicle as a school bus, even if the seller knows the vehicle will be significantly used as a school bus. Similarly, it is not a violation of Federal law to use a noncomplying vehicle to transport school children. As noted above, that is because individual states, not the Federal government, regulate the use of motor vehicles. In the situation described in your letter, several issues must be addressed to determine whether the vans are subject to our school bus safety standards. The first issue is whether the vans are 'buses.' Since the vans are designed to carry more than 10 persons, the answer to that question is yes. The second issue is whether Upward Bound activities are considered 'school related events.' Although Oregon may have a specific definition of 'school related event' for the purpose of determining whether Linfield College must use certified school buses, with regard to Federal law, we conclude the answer is yes. That is, if a new bus were sold or leased to the college, we would consider the new vehicle as being sold or leased for a school related event. The goal of Upward Bound is to prepare the participating students for post- secondary education. That is also, of course, one of the goals of the secondary schools in the program. Your enclosure states that Upward Bound staff 'visit each high school on a weekly basis doing counseling and follow-up work with each student.' These regular ongoing visits could not happen without the cooperation of the secondary schools in the program. Accordingly, it appears to us that the Upward Bound program is an 'event related to' the secondary schools concerned, within the meaning of the Safety Act. The final issue is whether transporting Upward Bound students constitutes a significant use for the vans. Linfield College need not purchase certified new school buses for its general purpose vehicles, even though such vehicles may be used occasionally to transport Upward Bound students. On the other hand, if Linfield College purchases or leases the vans knowing that they will be significantly used to transport Upward Bound students, the seller who knows of such anticipated use must sell only properly certified school buses. For information regarding state requirements on the use of school buses, you may contact Mr. Donald Forbes, 135 Transportation Building, Salem, OR 97310, telephone (503) 378-6388. I hope this information is helpful to you. Sincerely, John Womack Acting Chief Counsel";

ID: 07-007542--29 Feb 08--sa--2

ID: 004718as

ID: 10855-2

Terrence S. Lockman, Investigator
Levin, Middlebrooks, Mabie,
Thomas, Mayes & Mitchell, P.A.
Attorneys-at-Law
P.O. Box 12308
226 South Palafox Place
Pensacola, FL 32581

Dear Mr. Lockman:

This responds to your request for an interpretation whether a Model Year (MY) 1981 Versa Sweeper road sweeper is a "motor vehicle" and therefore subject to the Federal Motor Vehicle Safety Standards (FMVSSs) that were in effect when the vehicle was manufactured. Further, you ask whether the Versa Sweeper had to comply with requirements for an occupant restraint system or for rollover protection. You explained that you are conducting an investigation, and that "At the time in question, the vehicle was being used in a construction zone, to sweep debris off the roadway."

I note, before beginning, that your letter had asked for certain information under the Freedom of Information Act (FOIA). NHTSA separately answered your FOIA request by letter dated May 22, 1995, from Ms. Heidi Coleman of my staff, Assistant Chief Counsel for General Law.

Yours is an unusual interpretation request. Typically, questions concerning whether a vehicle is a motor vehicle are raised around the time of manufacture of a vehicle or its importation into the country, and by a person knowledgeable about the intended use of the vehicle, such as the vehicle's manufacturer. In contrast, your question asks about another entity's vehicle 14 years after the vehicle's manufacture, which makes our response more difficult. We cannot say for certain what principles would have applied in 1981 concerning the Versa Sweeper, and our knowledge of the vehicle is limited to the information you provided. Thus, a conclusive answer is beyond our reach.

We can make the following observations, however. NHTSA applies several principles when making a determination of whether a vehicle is a motor vehicle. Section 102(3) of the National Traffic and Motor Vehicle Safety Act defined a motor vehicle as "a vehicle driven or drawn by mechanical power and manufactured primarily for use on public streets, roads, and highways . . . ." We are not certain, based on the information you provided, that the Versa Sweeper was manufactured for use on public highways. The literature you sent indicates that the Versa Sweeper is intended for "road maintenance sweeping and highway preparation cleaning." It appears that the vehicle might be a construction vehicle. Moreover, you indicated that the vehicle was being used in a construction zone "at the time in question." Construction-related vehicles generally are "motor vehicles" for purposes of our statute if they frequently use the highway going to and from job sites and stay at a job site for only a limited time. With regard to the 1981 Versa Sweeper, its use of the highway is unclear.

Assuming the Versa Sweeper had regularly used the highway, NHTSA's longstanding position has been that vehicles of unusual configuration that are incapable of obtaining speeds greater than 20 miles per hour (mph) are not required to comply with the FMVSSs. It is unclear how this principle applies to a 1981 Versa Sweeper. The material you enclosed indicates that the Versa Sweeper has "Infinitely variable speeds from 0-30 miles per hour...." It is unclear whether this means each Versa Sweeper can attain a speed of 30 mph or whether some, but not all, can. A Versa Sweeper that had a maximum speed of less than 20 mph is excluded. One that went over 20 mph might not have been.

You ask about requirements for occupant restraints and rollover protection. The agency has stated that "street sweepers"--that are motor vehicles--are trucks. In 1981, FMVSS No. 208, Occupant Crash Protection (49 CFR '571.208), required open-bodied light trucks to have a lap belt system. There was no rollover requirement.

If you have any further questions, please contact Ms. Dorothy Nakama of my staff at (202) 366-2992.

Sincerely,

John Womack Acting Chief Counsel

ref:VSA102(3) d:8/2/95 In 1994, the Safety Act was recodified, without substantial change, at 49 U.S.C. 30101 et seq. The motor vehicle" definition is set forth in section 30102(a).

ID: 1983-2.49

TYPE: INTERPRETATION-NHTSA

DATE: 08/23/83

FROM: AUTHOR UNAVAILABLE; Frank Berndt; NHTSA

TO: Autodrome de Linas-Montlhery/Union Technique de L'Automobile du Motorcycle et du Cycle (H. Le Guen)

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. H. Le Guen Laboratory Director Union Technique de L'Automobile du Motocycle et du Cycle Autodrome de Linas-Montlhery Linas, 91310 Montlhery France

Dear Mr. Le Guen:

This is in reply to your letter of July 27, 1983, to Mr. Vinson of this office asking several questions with respect to the amendment of Standard No. 108, June 2, 1983, which permits semi-sealed replaceable bulb headlamps.

First, you mention certain sealing specifications, contrasting them with references to designed openings, and ask for our comments on this. Although the design that Ford intends to use is not a vented system, the amendment does not specify or prohibit either vented or unvented systems. A vented system using the standardized replaceable light source and the O-ring seal is permissable if the headlamp passes all the recently adopted environmental tests.

With reference to your further questions, there are no tolerances on the dust test. You have also asked whether, assuming that a European type headlamp using the new light source "passes all tests mentioned in the amendment to F.M.V.S.S. 108, would it get D.O.T. approval?" If the lens-reflector unit is bonded, and if with the light source inserted the lamp meets U.S. photometric requirements and all environmental tests specified in the amend-ment, then the manufacturer of the lamp may apply the D.O.T. symbol to it. This is the certification that the lamp meets all applicable U.S. Federal motor vehicle safety standards. Under this self-certification process, the manufacturer, rather than D.O.T., approves the lamp for sale.

Finally, you have asked who will manufacture the new bulb and where you might be able to obtain test samples. Ford's initial supplier will be Sylvania/GTE, and you may write GTE Products Corp., West Main Street, Hillsboro, NH 03249, Attn: Mr. Richardson.

I hope this answers your questions.

Sincerely,

Frank Berndt Chief Counsel

LINAS, July 27, 1983

Mr. TAYLOR VINSON NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION 400 Seventh Street S.W. WASHINGTON D.C. 20590 U. S. A.

Our ref. HLG/RR/JP/83.1159.33 Signed by: Mr. RENDU

Dear Mr. VINSON,

After reading over pages 24690 to 24716 of the 02 June 1983 Federal Register an interesting discrepancy come up. On the first page (24690), second column lines 10 and 61, and the third column line 62 of the same page, indicate the new plastic headlamp is to be semi-sealed, the opening (for the bulb) non-sealed, the bulb being the sealing piece with its "O" ring seal. Later in the text, page 7 (24696), third column, line 46, (corrosion) mentioned are "drainholes, breathing devices, and other designed openings that are to be in their normal positions" during testing.

If you could please comment on this point and possibly clarify this new standard this would be most helpful to us. In addition, if you could please comment on : Are there any tolerances in the "dust test" ? If a glass lens, metal reflector, European type headlamp, (using the new standard bulb) passes all tests mentioned in the Amendment to F.M.V.S.S. 108, would it get D.O.T. approval? And who is going to manufacture, and where would we able to obtain a sample of the new "standard" bulb?

Thank you very much for your assistance and we hope to hear from you soon.

Sincerely,

H. LE GUEN LABORATORY DIRECTOR

ID: 1984-2.34

TYPE: INTERPRETATION-NHTSA

DATE: 07/20/84

FROM: AUTHOR UNAVAILABLE; Frank Berndt; NHTSA

TO: Hino Motors (U.S.A.) Inc.

TITLE: FMVSS INTERPRETATION

TEXT:

Ms. Margaret Moore Oba Hino Motors (U.S.A.) Inc. 200 Park Avenue Suite 4114-12 New York, N.Y. 10166

Dear Ms. Oba:

This responds to your letter regarding the Federal motor vehicle safety standard on brake systems applicable to a diesel truck equipped with an "air over hydraulic" brake system.

After examining your letter and the enclosed diagram of the braking system, we note that air pressure is used to transmit braking force from the driver, not merely to assist the driver in applying muscular force to hydaulic or mechanical components. A failure in air pressure would result in loss of braking force. Therefore, this brake system falls within the definition of hair brake system" in paragraph S4 of Standard No. 121, Air Brake Systems.

When the original final rule was issued on Standard No. 121 , Air Brake Systems, the preamble stated:

It should be noted that the term "air brake system" as defined in the standard applies to the brake configuration commonly referred to as "air over hydraulic," in which failure of either medium can result in complete loss of braking ability.

See Federal Register, February 27, 1971, at page 3817.

In 1972, the agency reiterated this interpretation in the preamble to the original final rule on Standard No. 105a (now, Standard No. 105), Hydraulic Brake Systems:

Standard No. 105a does not apply to vehicles equipped with "air over hydraulic" systems, which remain within the purview of Standard No. 121 , Air Brake Systems.

See Federal Register, September 2, 1971, at page 17971. Copies of these pages are enclosed.

Accordingly, the air over hydraulic diesel truck braking system described in your letter would have to meet the requirements of Standard No. 121, Air Brake Systems.

Sincerely, Frank Berndt Chief Counsel Enclosures

January 26, 1984 Mr. Frank Berndt Chief Counsel National Highway Traffic Safety Administration 400 Seventh Street, S.W. Washington, D.C. 20590

Dear Mr. Berndt:

I would like to request clarification regarding F.M.V.S.S. classification of brake systems. In a new model of diesel truck which we intend to import to the United States, we use a system called the "air over hydraulic" brake system. It is rarely used in America, and we are unsure whether it should fit within the definition of a hydraulic brake or an air brake, as it contains elements of both designs.

I am enclosing a simple diagram for your reference. In it, the blue line represents air, the red, fluid. As you can see, pressure exerted by the driver is carried by air to the hydraulic air serve. From there,force is then transmitted by fluid to the wheel brakes. The descriptions of brake systems in F.M.V.S.S. 105 (hydraulic) and 121 (air) define each category according to the medium transmitting force from the service brake control to the brake itself. If the unit which uses air is considered only as a form of power assistance, the air-over system should be included in the hydraulic brake definition.

However, if the air system from the pedal to the hydraulic servo is considered as an integral part of the brake and of equal value, then it would not be merely an assist to the hydraulic.

We would like to know into which category our brake system should fall. If my explanations or diagram are incomplete or unsatisfactory in any way, please do not hesitate to contact us for further clarification.

Sincerely yours, Margaret Moore Oba Encl: