ID: nht75-3.37

DATE: 11/21/75

FROM: AUTHOR UNAVAILABLE; G.G. Mannella for James B. Gregory; NHTSA

TO: National Association of Motor Bus Owners

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letters of November 12 and 13, 1975, in which you requested that the National Highway Traffic Safety Administration immediately suspend the effectiveness of Standard No. 121, Air Brake Systems, with respect to buses, without waiting until the end of a comment period. In a notice published November 13, 1975, 40 FR 52856, this agency proposed such a suspension with a 30-day comment period ending December 15, 1975.

Secretary Coleman has made clear his commitment to allowing adequate time for public comment on rulemaking actions. The normal minimum time for public comment on Department of Transportation actions has been established as 45 days. In this case, because of the special urgency of the matter, the period was reduced to 30 days. I believe we all recognize that this action is a significant one, affecting the performance and cost of most of the transit and intercity buses in the country. In these circumstances, it is our judgment that the 30-day period is the minimum that can be justified for comment by the interested public, and your request is therefore denied.

We also recognize, as you have pointed out, that for this short period there may be some uncertainty and some interruption of normal activities within the affected industries. We will make every effort to reach and announce a decision as soon as possible after the end of the comment period.

Sincerely,

ATTACH.

NATIONAL ASSOCIATION OF MOTOR BUS OWNERS

November 13, 1975

Honorable James B. Gregory -- Administrator, National Highway Traffic Safety Administration, Department of Transportation

Dear Dr. Gregory:

This will supplement my letter of November 12, 1975, in regard to the problems created by failure to make effective immediately the suspension of Motor Vehicle Safety Standard No. 121 requirements respecting the brake anti-lock system on buses.

We understand why the National Highway Traffic Safety Administration does not want to deny any opponent of the proposed suspension an opportunity to be heard. Also, we are sure NHTSA does not want to halt sales of buses for six weeks or so, to disrupt bus manufacturing schedules, to cause temporary lay-offs of employees, or to require purchasers of buses to choose between taking immediate delivery of a needed bus or saving some $ 1,300.00 by postponing acceptance of delivery. These are the consequences of failure to make the suspension effective immediately.

We offer the following solution which, in our opinion, will fully protect the rights of any protestant of suspension if one should appear.

We suggest the suspension be made effective immediately, provided, the manufacturer and purchaser of any bus sold between now and January 1, 1976, agree in writing to the installation of the anti-skid device on or before January 8, 1976, if the National Highway Traffic Safety Administration concludes that suspension of the MVSS-121 requirement is unwarranted.

Since NAMBO members will be attending their Annual Meeting in Phoenix beginning Saturday, November 15, I am turning this matter over to NAMBO's General Counsel, Drew L. Carraway, Esq. of the firm of Rice, Carpenter and Carraway. Mr. Carraway will be in touch with your General Counsel's office to ascertain whether our proposal is satisfactory and advise those of us in Phoenix of your decision on this important matter.

Sincerely yours,

Charles A. Webb -- PRES.

cc: Frank A. Berndt (Acting Chief Counsel); Richard Dyson (Chief Counsel's Office)

NATIONAL ASSOCIATION OF MOTOR BUS OWNERS

November 12, 1975

Honorable James B. Gregory -- Administrator, National Highway Traffic Safety Administration, Department of Transportation

Dear Dr. Gregory:

ON November 11, 1975, the National Highway Traffic Safety Administration issued a proposed amendment of Motor Vehicle Safety Standard No. 121, Air Brake Systems, 49 CFR 571.121, to suspend, until January 1, 1977, service brake stopping distance requirements as they apply to buses.

In its tentative findings the Administration correctly noted that the present anti-lock system in buses is "characterized by malfunction that warrants its deactivation on all vehicles on which it is installed while a correction is fully developed" and that "a situation wherein purchasers of new buses are required to pay for anti-lock systems which are to remain deactivated for an indefinite period is inappropriate. NAMBO agrees with these findings.

The publication of this notice of proposed amendment of MVSS No. 121 creates a further problem for bus manufacturers since potential bus buyers will not purchase buses manufactured prior to whatever date the NHTSA may publish a final rule in the Federal Register due to the problems created by the anti-lock components as well as their cost.

Therefore, NAMBO urges the Administration to authorize the suspension of installation of potentially defective anti-lock components in buses pending a decision on the proposed amendment to MVSS No. 121.

The Annual Meeting of our Association begins on Sunday, November 16, in Phoenix, Arizona, at which time we will discuss and prepare a detailed explanation of the problems which would be created if the suspension cannot be made effective immediately. Our letter will be hand delivered to you on Thursday, November 20, with a copy to Mr. Richard Dyson of the Chief Counsel's Office.

Sincerely yours,

Charles A. Webb -- PRES.

cc: Richard Dyson

ID: nht75-3.38

DATE: 11/24/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Hon. J. P. Murtha - H.O.R.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your November 5, 1975, request for the criteria necessary for construction of testing equipment used to demonstrate compliance with Standard No. 121, Air Brake Systems.

The motor vehicle safety standards, including Standard No. 121, are established as requirements that vehicles must be capable of meeting if tested by the National Highway Traffic Safety Administration (NHTSA). However, the standards are not developed as demonstration procedures that detail methods a manufacturer would use to establish that its products comply. The development of actual test protocols to determine that products conform to the requirements is the responsibility of the regulated industry and the associated industries that service them.

Thus the Thiele Corporation, as a manufacturer of air-braked vehicles, may choose whatever test method gives it an adequate basis for certification that its products comply (15 U.S.C. @ 1397 (a)). Test equipment has been developed by several commercial sources, and Thiele can choose proper systems by consulting with the manufacturers of the brake components it uses. As for specifications for a test track, actual road tests are not necessary to establish compliance with Standard No. 121 where other reasonable means, such as engineering calculations coupled with laboratory tests, can be used to the same effect. Supplier warranties and instructions are one of the primary means by which smaller assemblers ascertain that their products conform.

Sincerely,

ATTACH.

CONGRESS OF THE UNITED STATES

House of Representatives

November 5, 1975

Richard B. Dyson, Chief Counsel -- National Highway Traffic Safety Administration

Dear Mr. Dyson:

Mr. William Wells of Thiele, Inc., a private truck building company, has requested that I inquire about the requirements for testing equipment under the Motor Vehicle Safety Standard 121 that went into effect in March of 1975.

Mr. Wells is interested in testing his own vehicles rather than bringing them to a professional testing track. Will you please inform me, in writing, what the criteria are for a company to build its own testing equipment in order to conform with the safety standards.

Thank you for your assistance in this matter.

Sincerely,

JOHN P. MURTHA -- Member of Congress

ID: nht75-3.39

DATE: 09/10/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Duo-matic Importers LTD.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Duo-matic's August 19, 1975, question whether Standard No. 121, Air Brake Systems, applies to an air brake coupler device that connects air brake hoses from a truck to the trailer it tows.

The answer to your question is no. Paragraph S3 (Applicability) of Standard No. 121 states that the standard applies to trucks, buses, and trailers equipped with air brake systems (with some stated exceptions). The standard therefore applies only to vehicles, and does not apply to motor vehicle equipment such as the Duo-matic coupler device.

SINCERELY,

August 19, 1975

Richard B. Dyson Assistant Chief Council Office of the Chief Council Federal Highway Administration

Refer to: A: Your letter N-40-30(MIS) dated 6-3-75

B: Motor Vehicle Safety Standard #121 as amended S5.3.3 Brake Actuation Time. With attached amendments of 11-12-74, 1-7-75, 1-17-75, 3-4-75, 3-21-75, 3-26-75, 5-15-75, and 6-11-75.

C: Duo-Matic Double Quick Release Coupling for Semi-Trailers (452-803)

D: Duo-Matic Double Quick Release Coupling for Towing Trailers (452 802)

The question is if Reference B above applies to our Wabco Westinghouse Duo-Matic coupler, which replaces the Glad Hand coupling now in use.

Your interpretation would be very much appreciated. We have enclosed two copies each of references C & D.

H. Melvin Strand, President

ID: nht75-3.4

DATE: 11/05/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: General Electric Company

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of July 8, 1975, to Ed Leysath of this agency concerning wattage requirements for Type 1A and 2A headlamps.

Your specific question is whether the wattage specifications in Federal Motor Vehicle Safety Standard No. 108 for Type 1A and 2A headlamps are design wattages or maximum wattages.

Paragraph S4.1.1.21(b) of Standard No. 108 specifies that, "Each Type 1A headlamp shall be designed for a maximum of 50 watts. Each Type 2A headlamp shall be designed for a maximum of 60 watts for each filament." (Emphasis added.) It follows, therefore, that the 50 - and 60-watt values are design wattages. You are correct in your interpretation that a tolerance of approximately 7.5% applies to these values, and that an ampere value of 4.20 for a 50-watt filament and 5.02 for a 60-watt filament is permitted. The 7.5% tolerance as you know is the average actual maximum wattage (as opposed to design wattage) rating of headlamps listed in Table 2 of SAE Standard J573 as determined by multiplication of the maximum amperage times the design volts.

Sincerely,

ATTACH.

GENERAL ELECTRIC COMPANY

July 8, 1975

Ed Leyseth -- National Highway Traffic Safety Administration, Department of Transportation

Subject: FMVSS 108 - Section 4.1.1.2.1

Dear Mr. Leyseth,

On March 26, 1975 I wrote to Bill Eason and requested an interpretation of the wattage requirements of the rectangular headlamp system. (copy enclosed). To date we have heard nothing and we urgently need your reply.

I would appreciate your help in providing us with your interpretation as quickly as possible.

Very truly yours,

Frank W. Bowers -- Manager, Product Reliability

attach: copy of 3/26/75 letter March 26, 1975

William Eason -- National Highway Safety Administration, Department of Transportation

Subject: FMVSS 108 - Section 4.1.1.21

Dear Mr. Eason:

I have heard that the Department of Transportation has interpreted Section 4.1.1.21(6) of FMVSS as far as the wattage limitation on Type 1A and Type 2A rectangular headlamps is concerned.

It is my understanding that the 50 watt limit on the Type 1A and the 60 watt limit on the 2A apply as design maximums and that a tolerance of approximate 7.5% applies to these values. This, then, would permit a max. ampere value of 4.20 for a 50 watt filament and 5.02 for a 60 watt filament. If a 40 watt filament is used than its max. amperes would be 3.36.

I agree with this interpretation and understand that these are the figures that SAE is proposing.

I would appreciate it very much if you would confirm that this interpretation is correct since design and certification of the product depends upon an accurate interpretation of the standard.

Thanks very much for your help in this matter.

Very truly yours,

F. W. Bowers -- Manager, Product Reliability

bcc: R. G. Burnor #1200

ID: nht75-3.40

DATE: 06/01/75 EST

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

TO: Floyd, Kramer & Lambrecht

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your letter of April 25, 1975, concerning the applicability of Federal Motor Vehicle Safety Standard No. 106-74, Brake Hoses, to the Wabco Westinghouse Duo-Matic Coupler.

You have described the Coupler as a device which replaces the glad hand coupler now used by most manufacturers to connect truck tractor and trailer brake lines. Because the brake hose which attaches to the Coupler is equipped with its own end fittings, the Coupler itself is not an end fitting. Therefore, Standard No. 106-74 is inapplicable.

The Coupler is, however, subject to the requirements of 49 CFR Part 393.45 and 393.46, of which I have enclosed a copy. Please direct any questions you may have concerning interpretation of these requirements to the Office of the Chief Counsel, Federal Highway Administration, at 400 Seventh St., S.W., Washington, D.C. 20590.

YOURS TRULY,

DOUBLE QUICK-RELEASE COUPLING DUO-MATIC "SEMTRA" FOR SEMI-TRAILERS

DUO-MATIC "SEMTRA" is a compressed air brake coupling for fitting on semi-trailers.

* No possibility of confusing the lines when connecting up.

* Simple to fit with or without attaching plate.

* Cover closes automatically -- no lost covers.

* Valves placed in the hose part.

* Takes up little room.

Ordering example: 452 803 500 0 Trailer part and towing vehicle part.

452 805 000 0 Towing vehicle part

For other combinations, see table.

PATENTED TRAILER PART TOWING VEHICLE PART TRAILER PART ASSEMBLY NO. ASSEMBLY NO. TOWING VEHICLE PART ASSEMBLY NO. 452 803 000 0 452 805 000 0 452 803 500 0 [Graphics omitted]

TOWING VEHICLE PART 452 805 000 0 Item Qty Part No. Description 1 1 152 805 230 1 Hose connection 2 2 896 010 680 1 Valve spring 3 2 152 802 190 1 Valve cap 4 2 897 181 100 1 Cylinder seal 5 2 805 070 430 1 Dished washer 6 2 810 518 018 1 Locking ring 7 2 899 504 400 2 Valve assembly 8 1 452 801 650 1 Dust cover 9 1 896 200 710 1 Spring 10 1 892 222 200 1 Shaft

Part marked x are included in spare parts set. E Packenhen kompl. Best. no. 452 805 000 2

TRAILER PART 425 803 000 0 Item Qty Part No. Description 4 1 152 802 100 1 Bracket 5 2 152 803 230 4 Sleeve 6 2 891 500 451 1 Nut 7 2 895 110 750 4 Press ring 8 1 452 802 550 1 Bettom plate 9 1 452 802 610 1 Dog for cover 10 1 452 802 555 1 Upper cover 11 2 452 802 690 1 Shaft 12 4 895 222 330 1 Locking ring 13 4 152 802 710 1 Lever 14 1 152 802 553 1 Holding-down P.

15 1 800 200 700 1 [Illeg.] springs 16 1 896 010 690 1 Compr. spring

Part marked x are included in spare parts set. E Packehen kompl. Best. no. 152 803 000 2

FITTING OF DUO MATIC "SEMTRA" ON SEMI-TRAILER IN ACCORDANCE WITH AMERICAN METHODS

[Graphic omitted]

ID: nht75-3.41

DATE: 08/25/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: National Solid Wastes Management Association

TITLE: FMVSS INTERPRETATION

TEXT: This responds to the National Solid Wastes Management Association's July 29, 1975, question whether Standard No. 121, Air Brake Systems, or other Department of Transportation regulations require a vehicle operator to maintain and not disconnect brake components used in satisfaction of the standard. You state that you are already aware of operator responsibilities to meet the regulations of the Bureau of Motor Carrier Safety and those promulgated by State and local governments.

Section 108(a)(1)(A) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1397(a)(1)(A)) specifies in part that no person shall sell or introduce in interstate commerce a vehicle which does not comply with applicable standards in effect on the date of manufacture. Section 108(b)(2) provides that @ 109(a)(1)(A) does not apply after the first purchase for purposes other than resale. The general effect of these provisions is that the brake system must comply and not be disconnected prior to its first retail sale. Section 108(a)(2)(A) provides that no manufacturer distributor, dealer, or motor vehicle repair business shall knowingly render inoperative a device installed in compliance with an applicable safety standard. Taken together, these provisions do not require the vehicle operator to maintain or not render inoperative a safety system after the first retail purchase. This agency does not recommend disconnection of elements of a brake system, however, in view of the probable adverse effect on handling not intended by the vehicle designer and engineer.

Other than the regulations of the Bureau of Motor Carrier Safety, of which you are aware, no regulations of the Department of Transportation require the maintainence or prohibit the disconnection of systems installed in satisfaction of motor vehicle safety standards.

SINCERELY,

National Solid Wastes Management Association

July 29, 1975

James Schultz Chief Counsel NHTSA

On March 1, 1975 FMVSS 121 Air Brake Systems became effective. It is our understanding that the vehicle manufacturer is responsible for complying with MVSS 121. Are there any requirements pursuant directly from MVSS 121 or indirectly from general applicability of DOT safety standards, which place responsibilities upon the vehicle operator to maintain or not to disconnect MVSS 121 equipment?

We are aware of the applicability of BMCS regulations upon interstate carriers and that often state legislatures and/or transportation departments often adopt Federal regulations and standards. However, clarification is desired pertaining to the implications of MVSS 121 on the vehicle operator, directly and indirectly.

James R. Greco Technical Director

ID: nht75-3.42

DATE: 10/10/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Kelsey-Hayes Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Kelsey-Hayes Company's July 28, 1975, question asking whether the requirements of S5.1.6 of Standard No. 121, Air Brake Systems, that specify a warning signal "in the event of a total electrical failure of the antilock system" would permit installation on a vehicle of an antilock-equipped axle that has no capability to signal electrical failure of its antilock system. You state that the vehicle would be equipped with antilock systems on other axles that would provide a warning signal in the event of their electrical failure.

The answer to your question is yes. As you noted in your letter, the National Highway Traffic Safety Administration has interpreted the specifications of S5.1.6 to require a signal only in cases where electrical failure within the antilock electrical system circuitry causes loss of antilock control of every wheel on the vehicle. In the design you describe, the signal which activates upon loss of antilock control at one or more wheels on the vehicle would fulfill this requirement, because it would always activate by the time antilock control had been lost at every wheel on the vehicle. Under our interpretation of S5.1.6, a failure of antilock only on the axle described by you would not constitute "loss of antilock control of every wheel on the vehicle" and would not be required to be signaled.

SINCERELY,

KELSEY-HAYES COMPANY

July 28, 1975

National Highway Traffic Safety Administration

ATTN: James Schultz Chief Counsel

RE: Request for Interpretation FMVSS-121: Air Brake Systems 5.1.6, Antilock Warning Signal

Kelsey-Hayes Company, a domestic manufacturer of motor vehicle equipment including antilock systems, requests an interpretation of the above referenced section of Standard 121 as it relates to tag axles, liftable axles and removable dollies.

Interpretations on this section of the standard issued by your staff in the past, specifically one to Wagner Electric on May 26, 1972 and another to the Eaton Corporation dated December 26, 1974 state that the phrase "total electrical failure" means any electrical failure within the antilock electrical system circuitry which would cause loss of antilock control of every wheel on the vehicle.

Since an antilock system failure on one axle need not actuate the warning signal, we ask whether it is consistent with these interpretations to equip an axle on a vehicle, specifically a tag axle, liftable axle, or removable dolly, with an antilock system that does not have the capability to activate the warning signal in the event of an electrical failure. Electrical failures which would disable the antilock system on the wheels of the other axles would activate the warning signal such that the "total electrical failure" situation would be complied with. In other words, the total electrical failure situation cannot occur unless the antilock systems on the other axles are disabled and, if they are, the warning signal will be activated.

We have been advised by installers of tag axles that it is burdensome to match the antilock system of the tag axle with the same make as those originally equipped on the other axles of the vehicle and that making the necessary electrical connections to the failure detection circuits on the other axles creates unacceptable liability risks. The most practical means to mitigate this condition would be to use trailer type antilock system components, which do not have electrical failure detection capability, for tag axles and other axles customarily added by body builders, etc.

Your prompt attention to this request for interpretation will be appreciated.

John F. McCuer

ID: nht75-3.43

DATE: 10/10/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Truck Body and Equipment Association

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your September 8, 1975, question whether trucks that carry specialized equipment (such as emergency medical equipment, fire fighting apparatus, or mobile power generator equipment), would qualify for exclusion from Standard No. 121, Air Brake Systems, if they are geared down or governed so that their speeds attainable in two miles are not more than 45 mph. You state that each vehicle's empty weight is more than 95 percent of its gross vehicle weight rating (GVWR).

The section of Standard No. 121 that lists the vehicles to which the standard applies reads as follows:

S3. Applicability. * * * In addition, the standard does not apply to any trailer whose unloaded vehicle weight is not less than 95 percent of its GVWR, or any vehicle that meets any one of criteria (a) through (d) as follows:

(d) (1) A speed attainable in two miles of not more than 45 mph; and

(2) An unloaded vehicle weight that is not less than 95 percent of the vehicle GVWR; and

(3) No passenger-carrying capacity.

From your description, it would appear that these vehicles would qualify for exclusion under category (d) of Section S3. The National Highway Traffic Safety Administration assumes that your description of emergency medical vehicles does not include an ambulance equipped with air brakes.

Sincerely,

TRUCK BODY AND EQUIPMENT ASSOCIATION, INC.

September 8, 1975

Richard Dyson, Assistant Chief Counsel National Highway Traffic Safety Administration

The recent amendment to FMVSS 121 relieving vehicles with an empty weight greater than 95% of the GVWR, no passenger or cargo carrying capacity and incapable of speeds in excess of 45 mph, from standard compliance has caused a number of questions from the truck body industry.

The questions center around a number of special duty vehicles designed and built to transport their self contained equipment rather than cargo. Examples of these vehicles would include: 1. Emergency communication vehicles

2. Emergency medical vehicles

3. Emergency electrical supply vehicles

4. Fire apparatus

Each of these vehicle types is generally completed on a commercial truck chassis with a piece or pieces of permanent equipment and its associated enclosures, i.e. large output generator sets, aerial ladder or elevating platform, mobile medical equipment. The chassis portion serves only as a means for transporting these pieces of equipment to the job site.

Where these vehicles are not designed or equipped to carry passengers or cargo, and their empty weight is always above 95% of the GVWR, are we correct in assuming that if the subject vehicles are physically restricted (governed, geared etc.) to speeds less than 45 mph then FMVSS 121 does not apply.

Byran A. Crampton Manager of Engineering Services

ID: nht75-3.44

DATE: 09/11/75

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

TO: Lear Siegler, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: I appreciate your letter of August 13, 1975, forwarding a copy of Neway's publication on Standard No. 121, Air Brake Systems. The efforts of companies like Neway to assist final-stage manufacturers in their certification responsibility has been an important part of the implementation of the air brake systems standard.

You asked for review of the booklet, which consists mainly of instructions to manufacturers concerning systems that must be tested and how to establish a basis for certification. This is an area which our statutory scheme leaves to the manufacturer, and in which, aside from discussions of general principles, this agency declined to issue statements of approval. While we appreciate the usefulness of the advice contained in your booklet, we regret that we can not judge the adequacy of a certification program in the abstract.

YOURS TRULY,

LEAR SIEGLER, INC.

NEWAY DIVISION

August 13, 1975

Richard Dyson Assistant Chief Counsel U.S. Department of Transportation National Highway Traffic Safety Adm.

I thought you would be interested in reviewing the enclosed copy of our FMVSS-121 booklet. If you wish additional copies, they are available.

This represents our interpretation of the Safety Standard and our recommendations to the industry in order to guide them in compliance with FMVSS-121.

We would appreciate your critical review of this booklet and any comments that you may have.

Ed Young

LEAR SIEGLER, INC.

NEWAY DIVISION

July 21, 1975

GENTLEMEN: Federal Motor Vehicle Safety Standard No. 121 (FMVSS-121) is a Department of Transportation Safety Standard defining brake system equipment and braking performance to be met by nearly all vehicles with air brake systems. Its purpose is to insure safe braking performance under normal and emergency conditions and is applicable to trucks, tractors, trailers and buses equiped with air brakes. Most trailers manufactured after December 31, 1974, and most trucks, tractors and buses manufactured after March 1, 1975, must meet the requirements of FMVSS-121. FMVSS-121 is in fact a law within which we must abide and conduct our business. Confusing? - complicated? - cumbersome? - Costly? YES! Impossible to deal with and comply? No! Difficult? Maybe at first but it too will come to pass and fall within our experteise and we shall take it in our stride.

FMVSS-121 is to be reckoned with so let us jointly accept it as reality and do everything in our power to comply with the law. Our heavy duty trucking customers are still going to rely on us to supply them with completed, road-ready vehicles, properly certified and meeting all applicable Federal Motor Vehicle Safety Regulations and standards. And it can be done. It is in this spirit that we offer this manual to be used as a guide in installing add-on, non-powered axles to new truck and tractors.

Edward L. J. Young

Director of Engineering

ID: nht75-3.45

DATE: 06/06/75

FROM: AUTHOR UNAVAILABLE; J. C. Schultz; NHTSA

TO: TTMA

TITLE: FMVSS INTERPRETATION

TEXT: This responds to the Truck Trailer Manufacturers Association's May 1, 1975, request for a determination of what speed the National Highway Traffic Safety Administration (NHTSA) considers as "highway speeds" in establishing gross vehicle weight ratings (GVWR) and gross axle weight ratings (GAWR) under the requirements of 49 CFR @ 567.4 (g)(3) and (4).

For purposes of GVWR-GAWR calculations, NHTSA will consider "highway speeds" to be the 60 mph value used by the United States Tire and Rim Association in assigning unqualified ratings to their tires. Therefore, trailers which are capable of speeds of 60 mph or more should be assigned ratings which reflect vehicle capabilities at 60 mph.

SINCERELY,

May 1, 1975

James C. Schultz Chief Counsel National Highway Traffic Safety Administration

In regard to your letter of March 5, 1975, you state that "A vehicle capable of highway speeds and reasonably expected to be operated at such speeds is subject to Standard No. 121 - Air Brake Systems at weight ratings specified for highway speeds".

Advice would be greatly appreciated as to the numerical value NHTSA has assigned to the term "highway speeds".

Don W. Wieriman Staff Engineer-Tank Vehicles