ID: 7331

Christian Hammarskjold
Vice President
USSC Group, Inc.
20 Union Hill Road
West Conshohocken, PA 19428

Dear Mr. Hammarskjold:

This responds to your letters of May 28, 1992 concerning suspension seats. Your first letter states that you have been asked by SCRTD in Los Angeles to develop a system that will allow your suspension seats for the driver's seating position in transit buses to tilt from side-to-side. Your letter states:

In addition, USSC is concerned that there are not applicable FMVSS requirements that address a side-to- side strength requirements. 207/210 requires a pull from the front of the seat. What happens if there is a side impact on a suspension seat that has a ball and socket joint. Are there any applicable performance requirements that may apply to such a system.

With respect to seats which tilt side-to-side, you are correct that Federal Motor Vehicle Safety Standard No. 207, Seating Systems, does not include a performance requirement addressing side-to-side strength. Standard No. 207 requires certain specified forces to be applied only in a forward direction and in a rearward direction. All seats, in all vehicles, except for side-facing seats or passenger seats in buses, must be capable of withstanding these forces when tested in accordance with the S5 of Standard No. 207.

However, you should be aware that manufacturers are subject to the requirements in 151-159 of the Safety Act concerning the recall and remedy of products with safety defects. The defect responsibility is a broad one and would include the side-to-side performance of your seat. In the event that NHTSA or a manufacturer determines that a vehicle containing your seat has a safety-related defect, the manufacturer would be responsible for notifying purchasers of the defective equipment and remedying the problem free of charge. You may be interested in a current proposal to amend Standard No. 207 to establish revised test procedures for pedestal seats. I have enclosed a copy of the notice for your information.

Your second letter asks when shoulder belts will be required on suspension seats. The safety belt installation requirements are set forth in Standard No. 208, Occupant Crash Protection. This standard specifies requirements based on vehicle type and seating position within the vehicle, not based on seat design. I have limited the following discussion of safety belt requirements to trucks and buses, as I am unaware of any passenger cars or multipurpose passenger vehicles which contain suspension seats. As explained below, shoulder belts are required at every forward-facing outboard seating position in trucks with a GVWR of 10,000 pounds or less; at the driver's seating position and at every forward-facing outboard seating position in buses, other than school buses, with a GVWR of 10,000 pounds or less; and at the driver's and right front passenger's seating positions in school buses with a GVWR of 10,000 pounds or less. Shoulder belts are not required at any other seating positions in these vehicles or in trucks or buses with a GVWR of more than 10,000 pounds.

The requirements for trucks are contained in sections S4.2 and S4.3 of Standard No. 208. Sections S4.2.2 and S4.2.3 of Standard No. 208 give vehicle manufacturers a choice of three options for providing occupant crash protection in trucks with a GVWR of 10,000 pounds or less, manufactured on or after September 1, 1991 and before September 1, 1997. Option 1, set forth in S4.1.2.1, requires vehicle manufacturers to provide automatic protection at the front outboard seating positions, lap or lap/shoulder belts at all other seating positions, and either meet the lateral crash protection and rollover requirements by means of automatic protection systems or have manual safety belts at the front outboard seating positions such that those positions comply with the occupant protection requirements when occupants are protected by both the safety belts and the automatic protection. Option 2, set forth in S4.1.2.2, requires vehicle manufacturers to provide a lap or a lap/shoulder safety belt at every seating position, have automatic protection for the front outboard seats, and have a warning system for the safety belts provided. Option 3, set forth in S4.1.2.3 requires the manufacturer to install lap or lap/shoulder safety belts at every seating position and to have a warning system for those belts. In addition, each Type 2 seat belt assembly (i.e., lap/shoulder safety belts) installed at a front outboard seating position in trucks with a GVWR of 8,500 pounds or less must satisfy the dynamic testing requirements in S4.6.

S4.2.4 of Standard No. 208 specifies that a Type 2 seat belt assembly must be installed at each forward-facing rear outboard seating position in trucks with a GVWR of 10,000 pounds or less, manufactured on or after September 1, 1991.

Section S4.2.5 of Standard No. 208 specifies a phase-in of trucks and buses with a GVWR of 8,500 pounds or less that must satisfy the requirements of S4.1.2.1 (Option 1 above). Twenty percent of trucks and buses manufactured on or after September 1, 1994 and before September 1, 1995 must meet this requirement; 50 percent of trucks and buses manufactured on or after September 1, 1995 and before September 1, 1996; 90 percent of trucks and buses manufactured on or after September 1, 1996 and before September 1, 1997. All trucks and buses with a GVWR of 8,500 pounds or less manufactured on or after September 1, 1997 must comply with the requirements of S4.1.2.1.

Section 4.3.1 gives vehicle manufacturers a choice of two options for providing occupant crash protection in trucks with a GVWR of more than 10,000 pounds manufactured on or after September 1, 1990. Option 1, set forth in S4.3.1.1, requires vehicle manufacturers to provide an automatic protection system at all seating positions that meets the frontal and lateral crash protection and rollover requirements. Option 2, set forth in S4.3.1.2 requires vehicle manufacturers to install lap or lap/shoulder belts at every seating position. In addition, S4.3.2 specifies that, if a manufacturer chooses to comply with Option 2, the lap belt or pelvic portion of a lap/shoulder belt must have either an emergency locking retractor (ELR) or an automatic locking retractor (ALR).

The requirements for buses are contained in S4.4 of Standard No. 208. Section 4.4.1 gives vehicle manufacturers a choice of two options for providing occupant crash protection in buses manufactured on or after September 1, 1990. Option 1, set forth in S4.4.1.1, requires vehicle manufacturers to provide an automatic protection system at the driver's seating position that meets the frontal and lateral crash protection and rollover requirements. Option 2, set forth in S4.4.1.2 requires vehicle manufacturers to install a lap or lap/shoulder belt at the driver's seating position. In addition, S4.4.2.2 specifies that, if a manufacturer chooses to comply with Option 2, the lap belt or pelvic portion of the lap/shoulder belt must have either an ELR or an ALR.

Section S4.4.3 requires buses, other than school buses, with a GVWR of 10,000 pounds or less, manufactured on or after September 1, 1991, to have a lap/shoulder belt at the driver's seating position and at every front and rear forward-facing seating position, and either a lap belt or a lap/shoulder belt at every other seating position. School buses with a GVWR of 10,000 pounds or less, manufactured on or after September 1, 1991, are required to have a lap/shoulder belt at the driver's and right front passenger's seating positions, and either a lap belt or lap/shoulder belt at every other seating position. As mentioned previously, buses with a GVWR of 8,500 pounds or less manufactured on or after September 1, 1994 are subject to the phase-in requirement for automatic occupant protection.

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

Sincerely,

Paul Jackson Rice Chief Counsel

Attachment

ref:207#208 d:8/10/92

ID: 7333

Mr. Joe Wos
A & D Lock & Key
238 Faithway Dr.
Seffner, FL 33584

Dear Mr. Wos:

This responds to your May 26, 1992 letter asking whether it is "legal to repair an automobile that has an airbag deployed and not put the air bag back in."

I am enclosing a copy of a January 19, 1990 letter to Ms. Linda L. Conrad, that explains whether a used car dealer has an obligation to replace a deployed air bag prior to selling the car. The same statutory and regulatory considerations that applied to that situation would apply to the replacement of a damaged air bag steering column (after the air bag has deployed) with a steering column without an air bag.

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

Sincerely,

Paul Jackson Rice Chief Counsel

Enclosure

ref:208 d:6/24/92

ID: 7339

C.N. Littler
Coordinator, Regulatory Affairs
Motor Coach Industries
552 West Stutsman Avenue
Pembina, North Dakota 58271

Dear Mr. Littler:

This responds to your letter of May 25, 1992, concerning possible federal preemption of a bill that has been introduced in the New York State legislature. The bill would require any intercity bus that is operated in the State of New York manufactured on or after July 1, 1993 to be equipped with safety belts at every seating position, unless the bus is operated by a motor carrier which does not operate annually more than 100 days or more than 10,000 vehicle miles within the State of New York. After reviewing the copy of this bill enclosed with your letter, we have concluded that it appears to be preempted by Federal law, to the extent that it requires the installation of seat belts for passenger seats of buses that have a gross vehicle weight rating (GVWR) of more than 10,000 pounds and that are not State-owned vehicles. This conclusion is explained in detail below.

Section 103(d) of the National Traffic and Motor Vehicle Safety Act (the Safety Act; 15 U.S.C. 1392(d)) states:

Whenever a Federal motor vehicle safety standard ... is in effect, no State or political subdivision of a State shall have any authority either to establish, or to continue in effect, with respect to any motor vehicle or item of motor vehicle equipment any safety standard applicable to the same aspect of performance of such vehicle or item of equipment which is not identical to the Federal standard. Nothing in this section shall be construed to prevent ... any State or political subdivision thereof from establishing a safety requirement applicable to motor vehicles or motor vehicle equipment procured for its own use if such requirement imposes a higher standard than that required to comply with the otherwise applicable Federal standard. Section 103(d) preempts New York's proposed law if that law covers the same aspect of performance as an applicable Federal motor vehicle safety standard, and is different from the applicable Federal standard, with one exception. It would not preempt the law to the extent that the law imposes a higher level of performance upon vehicles procured for use by the State or any of its political subdivisions.

In this case, Standard No. 208, Occupant Crash Protection (49 CFR 571.208) "specifies performance requirements for the protection of vehicle occupants in crashes." (S1 of Standard No. 208). Section S4.4 of Standard No. 208 specifies performance requirements for the protection of bus occupants. Accordingly, there is a Federal motor vehicle safety standard in effect and that standard establishes performance requirements for occupant protection in buses. The question then is whether the proposed New York State law, which applies to the same aspect of performance, is either identical to Standard No. 208's requirements.

The applicable performance requirements for occupant protection at passenger seats in buses manufactured on or after September 1, 1991, differ, depending upon whether the vehicle has a GVWR of 10,000 pounds or less or a GVWR of more than 10,000 pounds. For buses (other than school buses) with a GVWR of 10,000 pounds or less, S4.4.3.2 of Standard No. 208 requires a lap/shoulder belt to be provided at every forward-facing outboard seating position, and either a lap belt or a lap/shoulder belt to be provided at every other seating position. New York's law, requiring seat belts at every seating position in buses, would not be preempted with respect to these small buses if it were interpreted to require the same types of safety belts as required under Standard No. 208.

With respect to buses with a GVWR of more than 10,000 pounds, manufactured on or after September 1, 1991, S4.4.3.1 of Standard No. 208 requires compliance with either of two options for the driver's seating position, the installation of an automatic restraint or the installation of either a lap belt or lap/shoulder belt, and does not require any type of occupant protection system at any other seating position. NHTSA expressly determined that there is not a safety need for safety belts or another type of occupant crash protection at these seating positions. See, 39 FR 27585, July 30, 1974. With respect to these large buses, the New York bill would be preempted to the extent that it requires seat belts to be installed at seating positions other than the driver's seating position.

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

Sincerely,

Paul Jackson Rice Chief Counsel

ref:VSA#208 d:8/19/92

ID: 7353

Mr. Steven Rovtar
General Manager
Blazer International Corp.
2960 Hart Drive
Franklin Park, IL 60131

Dear Mr. Rovtar:

This responds to your letter of May 28, 1992, asking for "a written ruling" that the product you described "meets current SAE/DOT guidelines."

The product is intended for the vehicle towing trailer market. Currently, lamps on towed vehicles are activated by splicing into the wiring harness of the towing vehicle. Your product eliminates the need for this type of hard wiring. This product "utilizes photodetectors to read the output of the towing vehicle's stop and turn signal lamps, and in turn activate the lamps of the towed vehicle." Photodetectors are embedded in suction cups which are attached to the towing vehicle's stop and turn signal lamps. The device is plugged into the cigarette lighter receptacle of the towing vehicle, and the harness of the towed vehicle is plugged into the device. When the stop lamp or turn signals of the towing vehicle are activated, the photodetectors read the light emitted, and the towed vehicle's lamps are activated via the completed circuit.

For purposes of this discussion we shall assume that the device is intended for aftermarket distribution. Further, from your description, it appears to be the type of device that is simple enough to be installed by the vehicle owner. The product itself is not directly regulated by Federal Motor Vehicle Safety Standard No. 108 Lamps, Reflective Devices and Associated Equipment, because it is not replacement equipment intended to replace original equipment. Its installation on a vehicle in use by the vehicle's owner is outside the prohibition contained in the National Traffic and Motor Vehicle Safety Act. That prohibition forbids "manufacturers, distributors, dealers, and motor vehicle repair businesses" from "rendering inoperative, in whole or in part," mandated safety equipment such as stop lamps and turn signal lamps.

Were the device installed by a person in these categories we would be concerned that the addition of the suction cups would partially obscure the original equipment stop and turn signal lamps and, thus, render them "partially inoperative" within the meaning of the prohibition. That concern is not lessened by the fact that the device may be installed by a person not covered by the prohibition, such as the owner of the towing vehicle. However, as a practical matter, we realize that the safety impact may be minimal since the presence of the trailer will obscure the lamps on the towing vehicle to which the suction cups are applied.

We cannot advise you on whether the product meets SAE requirements. The legality of the use of equipment that is not regulated by NHTSA is determinable under the laws of States where the towing-towed vehicle combinations are operated. We are unable to advise you on these laws, and suggest that you write the American Association of Motor Vehicle Administrators, 4600 Washington Boulevard, Arlington, Va. 22203, for an opinion.

Sincerely,

Paul Jackson Rice Chief Counsel

ref:108 d:6/17/92

ID: 7378

Mr. Berkley C. Sweet
Vice President
School Bus Manufacturers Institute
7508 Ben Avon Road
Bethesda, MD 20817

Dear Mr. Sweet:

This responds to your letter of May 29, 1992 asking what minimum passenger size (weight and height) was used in developing the requirements of Federal Motor Vehicle Safety Standard No. 222, School Bus Passenger Seating and Crash Protection. You noted that several school districts are now transporting newborn and under-school-age children to schools which provide day-care service, and that you have received inquiries concerning the "limits, if any, on passenger size and age that can be safely transported on school bus seats."

The National Traffic and Motor Vehicle Safety Act, defines a "school bus" as a vehicle that "is likely to be significantly used for the purposes of transporting primary, preprimary, or secondary school students to or from such schools or events related to such schools." NHTSA has never specified a passenger size and/or age range applicable to the compartmentalized school bus seats required by Standard No. 222. In developing the standard, however, NHTSA considered the range of sizes and ages of children attending preprimary through secondary school.

NHTSA has developed approximate size and weight guidelines for child restraint systems. For children from birth to 9-12 months (or up to 20 pounds), NHTSA recommends use of an infant or convertible seat facing the rear. For children from 9-12 months to 4 years (or 20 pounds to 40 pounds), NHTSA recommends use of a convertible or toddler seat. If a school is transporting children in these age and weight ranges, they may want to consider using a school bus with safety belts to secure a child restraint system. I have enclosed a consumer information sheet titled "Transporting Your Children Safely" for your information.

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

Sincerely,

Paul Jackson Rice Chief Counsel

Enclosure

ref:571 d:7/28/92

ID: 7379

Mr. Mark W. Russo
1480 West Macopin Road
West Milford, NJ 07480

Dear Mr. Russo:

This responds to your letter of May 27, 1992, to Mr. Charles Gauthier of this agency, which enclosed a copy of R-Bar test data provided by Micho Industries. You requested an "official `review and comment'" regarding the applicability of Safety Standard 222 to the R-Bar Passenger Restraint System and related issues.

The National Highway Traffic Safety Administration (NHTSA) has addressed the use of "safety bars" in school buses on several occasions in the past. Enclosed for your information are copies of five NHTSA letters which address this subject and which, we believe, will also address your concerns. The letters are addressed to Mr. Michael F. Hecker of Micho Industries, dated May 14, 1992; Mr. Scott K. Hiler of the C. E. White Company, dated January 31, 1991; Honorable Robert J. Lagomarsino, Member of Congress, dated January 8, 1990; and Mr. Joseph F. Mikoll of Transportation Equipment Corporation, dated March 10, 1989 and November 3, 1988.

If, after reviewing the enclosed materials, you still have questions concerning this matter, please feel free to contact Mr. Walter Myers of my staff at this address or at (202) 366- 2992.

Sincerely,

Paul Jackson Rice Chief Counsel

Enclosures Ref: #222 d:7/l3/92

ID: 7383

Mr. Steven Henderson
Department of Psychology
McGill University
1205 Dr. Penfield
Montreal PQ H3A 1B1
Canada

Dear Mr. Henderson:

This responds to your letter of August 11, 1992, commenting on my response to you of June 29 with respect to the relationship of your motorcycle headlamp warning device to S5.6 of Federal Motor Vehicle Safety Standard No. 108, the provisions regulating the modulation of motorcycle headlighting systems.

In my letter, I informed you that the device would not comply with the requirements of Standard No. 108, and would affect compliance of the taillamps and turn signal lamps with the standard. I also advised you that if a motorcycle owner could install the device, there would be no violation of Federal law, and that the legality of its use would be determinable under the laws of the individual American states.

In your latest letter, you "agree that the device contravenes the letter of DOT Standard No. 108 as it presently stands." However, "if the device violates the letter of the law while satisfying the spirit or inferred intent of the law in each case," you believe "that the granting of an exception should be considered by the NHTSA."

As I understand it, your principal argument as raised on page 2 of your August 11 letter is that it is improper to consider your device under S5.6 as it is not a motorcycle headlamp modulating system as described in that section. Thus our objections to modulation rate and intensity, based upon the specifications of that section, are misplaced.

Assuming for the sake of argument that you are correct, your device becomes subject to another provision of Standard No. 108 that I did not mention in my June letter. Paragraph S5.1.3 prohibits the installation, as original equipment, of any motor vehicle equipment that impairs the effectiveness of lighting equipment that Standard No. 108 requires. Application of paragraph S5.1.3 returns us to my comments in June that your device would affect compliance of the taillamps and turn signal lamps with Standard No. 108. The taillamps would no longer be steady-burning, as required by S5.5.10(d). It would appear that the turn signal rate would also cease to comply with the flash rate of 60-120 per minute specified by SAE requirements incorporated by reference in Standard No. 108. Thus, under paragraph S5.1.3, installation of the device as aftermarket equipment, if performed by a manufacturer, dealer, distributor, or motor vehicle repair business would continue to be prohibited by Federal law.

Your latest letter also addresses the issues of taillamp and turn signal conformance. You argue that

"a taillight's purpose is to mark the rear of a motor vehicle during nighttime driving when it would otherwise be invisible. For this reason the law requires that taillights be lit at night. The law makes no such requirement during the day. The law does require that motorcycle headlights be lit during the day. * * * At night the taillight will always be steady-burning as required by S5.5.10(d) because the flasher device is only able to induce taillight flicker during daylight hours due to the photocell circuitry incorporated to prevent the headlamp from generating strobe effects at night. Therefore, the device is in compliance with S5.5.10(d) as it will cause the taillight to flash only at times that it is not required by law to be lit."

The law that applies to your argument is Standard No. 108. Paragraph S5.5.7(b) states in pertinent part that "On each . . . motorcycle . . . when the headlamps are activated in a steady-burning state, the taillamps . . . shall also be activated." Thus, under Standard No. 108 the taillamps must always be activated when the headlamps are activated.

The device also functions through the horn button to cause the turn signal lamps to flash at a rate higher than the maximum permitted by Standard No. 108. In your view, the situation in which the turn signal and horn button are in simultaneous use will be rare. However, if they are used together, "the SAE-specified turn signal flash of 1-2 hz will be perceptually present, the hazard signal flash of 10 hz will also be perceptually present at the same location, and the two signals will not interfere."

We consider that paragraph S5.1.3 applies here as well, and that a flash of 10 hz would impair the effectiveness of the required turn signal flash of 1-2 hz. There could be another undesirable consequence as well. When NHTSA proposed allowing modulating headlamps, commenters were concerned that the flashing might trigger a photic reaction, akin to an attack of epilepsy, in onlookers. NHTSA observed that the reaction was most likely to occur at a frequency of 10 hz against a very dark background. Although your device does not operate at night, its frequency is at the threshold where photic reactions can occur, and we want to bring this fact to your attention.

The agency shares your concern with improving the detectability of motorcycles and their riders. You have suggested writing an "exception" in Standard No. 108 for a period of one or two years so that the safety benefits of the device can be evaluated. We have a procedure under which a manufacturer of motorcycles can petition for a temporary exemption of up to two years, applicable to 2,500 vehicles per year, on the basis that it would facilitate the development and field evaluation of an innovative safety device. Perhaps you can interest a manufacturer in petitioning for a temporary exemption from Standard No. 108 on this basis.

You may also petition the agency for rulemaking to amend Standard No. 108 in a manner that would allow your device. A petition must set forth facts which it is claimed establish that a change in the standard is necessary, and a brief description of the changes which should be made. This means that you should show how your device is expected to improve safety, or, at a minimum, not decrease the existing level of safety. The agency has no plans to initiate rulemaking on its own initiative to permit your device.

Sincerely,

Paul Jackson Rice Chief Counsel

ref:108 d:8/28/92

ID: nht94-2.45

TYPE: INTERPRETATION-NHTSA

DATE: April 18, 1994

FROM: Fred Benford -- 100+ Motoring Accessories

TO: John Womack -- Acting Chief Counsel, NHTSA

TITLE: None

ATTACHMT: Attached To Letter Dated 5/16/94 From John Womack To Fred Benford (A42; Std. 211)

TEXT: Dear Mr. Womac:

The Chief Counsel of the Specialty Equipment Manufacturers Association (SEMA) reviewed all regulations covering wheel covers and suggested that we contact Mr. Truman Vincent. We explained our situation to Mr. Vincent who in turn, suggested that we addre ss our request to your attention.

We are a manufacturer of Aluminum Wheel Covers. They are a standard type and do not have any protrusions (e.g., spinners, etc.). With the assistance of the Chief Counsel at SEMA, the current regulations were reviewed and it was determined that our Alum inum Wheel Covers are similar in design to the Steel and ABS plastic type and are not covered by any regulations, except for # 211 which prohibits protruding objects such as spinners, etc. Our wheel covers do not have any protruding objects.

At the current time, we are the only manufacturers of Aluminum Wheel Covers. Because they are made of a different material from the current steel and ABS models, a major retailer has asked us to confirm that aluminum, like the ABS and Steel wheel covers, do not violate any federal safety standards. Considering information from our SEMA counsel, and Mr. Truman Vincent, we do indeed not violate any federal safety standards. However, the major retailer (and possibly others) has requested a confirmation i n writing from the Department of Transportation. We would appreciate a statement from you with wording to this effect to present to the retailer.

Thank you for your assistance. We would appreciate hearing from you quickly. If desired, you may fax your response to the phone listed below.

Sincerely,

ID: nht94-2.46

TYPE: INTERPRETATION-NHTSA

DATE: April 18, 1994

FROM: Robin Liu -- President, Introbusy

TO: Stephen Wood -- Transportation Department, NHTSA

TITLE: None

ATTACHMT: Attached To Letter Dated 6/6/94 From John Womack To Robin Liu (A42; Std. 108; VSA 108(a)(2)A)

TEXT: DEAR MR. WOOD:

WE ARE GOING TO IMPORT A MERCHANDISE OF STOPPING LAMP FOR AUTOMOBILES. ITS FEATURE AND USAGE ARE AS PER THE ATTACHED SHEETS/PHOTOS.

WE WOULD LIKE TO KNOW WHETHER IT MEETS THE REGULATION OF YOUR DEPARTMENT BEFORE WE PLACE ORDERS FOR IMPORTATION.

DO WE NEED TO GET ANY OFFICIAL APPROVAL OR TO APPLY ANY LICENSE TO ENSURE THAT INSTALLING THIS PRODUCT IN MOTOR VEHICLE WILL NOT VIOLATE THE REGULATION OF TRANSPORTATION DEPARTMENT?

SHOULD YOU NEED FURTHER DETAILS OR CLARIFICATION, PLEASE EITHER WRITE TO US AT THE ADDRESS UNDERNEATH OR CALL/FAX TO US AT (415) 468-3831.

WE LOOK FORWARD TO HEARING FROM YOU SOON.

SINCERELY YOURS

ID: nht94-2.47

TYPE: Interpretation-NHTSA

DATE: April 18, 1994

FROM: John Collins -- Senior Vice President, Government Affairs, American Trucking Associations (Alexandria, VA)

TO: John G. Womack -- Acting Chief Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 9/2/94 from John Womack to John Collins (A42; Std. 121)

TEXT:

This letter is a request for an interpretation of the test procedure specified in paragraph S5.8.2, "Supply line retention", of Federal Motor Vehicle Safety Standard (FMVSS) 121, "Air Brake Systems". The last sentence in this paragraph states:

"A trailer shall meet the above supply line retention requirement with its brake system connected to the trailer test rig shown in Figure 1, with the reservoirs of the trailer and test rig initially pressurized to 100 psi, and the regulator o f the test rig set at 100 psi."

Our interpretation of test conditions specified in this sentence and Figure 1 (copy attached) is that:

1. The test rig remains connected to the shop air, as shown in Figure 1, for the duration of the test.

2. The shut-off valve of the test rig remains open for the duration of the test.

3. The pressure in the test rig's 1000 cu in. reservoir is maintained at 100 psi for the duration of the test.

The basis for our interpretation are:

a. S5.8.2 does not say that the test rig is to be separated from the shop air supply for the test.

b. S5.8.2 does not say to turn the shut-off valve to the "off" position for the tests. The valve is considered to be normally "open" for tests since it is "open" during the tests for which the test rig was originally designed (brake apply a nd releasing timing tests in paragraphs S5.3.3 and S5.3.4 of FMVSS 121) and these paragraphs do not say to have the shut-off valve "open" the tests.

c. There would be no reason for S5.8.2 to specify setting the regulator valve at 100 psi if air was not flowing through the regulator valve. Air can only flow through the valve in this test when air is coming from the shop air supply and go ing out through the shut-off valve.

d. When a combination vehicle is moving, the vehicle's air compressor is operating to maintain the air system pressure within a specified range.

Whenever the trailer supply line pressure is less than the tractor reservoir pressure, air is flowing through the supply line.

We would very much appreciate an early answer to this request as The Maintenance Council of the American Trucking Associations is planning tractor- trailer air systems tests during the first week of May. The objective of these tests is to develop inform ation which will help manufacturers and owners build/modify equipment in such a way as to effectively live with the requirements of S5.8.2 as we interpret the.

Attachment

Figure 1. - Trailer Test Rig. (Graphics omitted.)