Interpretation ID: nht79-4.29

DATE: 08/15/79

FROM: AUTHOR UNAVAILABLE; Frank Berndt; NHTSA

TO: Nissan Motor Co. Ltd.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your letter of July 3, 1979, asking several questions concerning the definition of "designated seating position" (49 CFR 571.3), as that term was recently amended (44 FR 23229, April 19, 1979).

In your first question, you ask for confirmation that any bench or split-bench seat with less than 50 inches of hip room may never be required to have three or more than three designated seating positions, notwithstanding the capability of accomodating a person at least as large as fifth percentile adult female. Your assumption is incorrect. As noted in the (Illegible Word) to the recent amendment, the 50-inch specification does not mean that some vehicle seats with less than 50 inches of hip room should not also have more than two designated seating positions, if the vehicle and seat design is such that three positions would likely be used (44 FR 23232). The specification is nerely the amount of space the agency will consider as conclusive evidence that there should be at least three designated seating positions. The 50-inch caveat was included in the definition to simplify determinations of proper seating capacity by both manufacturers and the agency.

Your second question involves technical aspects of the amended definition of "designated seating position". The definition specifies that "hip room" is to be measured in accordance with SAE J1100(a). That standard defines "hip room" as,

"the minimum dimension measured laterally between the trimmed surfaces on the 'x' plane through the (Illegible Word) front Vithin 1.0 in. (25mm) below and 3.0 in. (76mm) above the SqRP-front and 3.0 in. (76mm) force and aft of the SqRP-front." (Area A in your diagrams.)

Your question includes diagrams and asks whether various portions of vehicle seats or other components would be considered "trimmed surfaces" within SAE Standard J1100(a).

Specifically, you ask whether slightly soft surfaces such as arm rests, seat back contours or other raised portions of the seat cushion would be considered "trimmed surfaces", for purposes of determining the minimum hip room dimension. The answer to your question is yes. The agency would probably consider all of the surfaces illustrated in your letter "trimmed surfaces" and, strictly speaking, within the meaning of the SAE procedure. This interpretation must be qualified, however. The procedure specifies that "hip room" is the minimum dimension "between trimmed surfaces". If a particular bench seat has distinct sections, the total dimension must be determined by adding the minimum dimensions of each section. For example, your Figure 5 illustrates a bench seat that includes a slightly raised center surface on the tunnel (in the center of the seat over the driveshaft). The lowest portion of Area A as defined in SAE J1100(a) would strike the side of this elevated center section, even though the top portion of Area A would be above the elevation. In such case, there would be three distinct portions of the seat (the driver's seat, the passenger seat, and the center seat position) that should be measured separately and then added together to get the total dimension. Otherwise, only the portion of the seat on the driver's side of the center elevation would be measured under the strict wording of the SAE procedure--an absurd result.

Regarding these questions about the measurement procedure, I must make several candid remarks. The agency will not allow manufacturers to avoid the obvious intent of the definition of "designated seating position" by finding loopholes in the measurement procedure. Further, as noted above, even if the hip room as measured in accordance with SAE J1100(a) is less than 50 inches, a manufacturer may still be required to designate three seating positions. If the measured dimension is less than 50 inches only because of slight elevations or contours on the outside seat cushion, a manufacturer must designate at least three positions if these elevation or contours are not real impediments to three persons occupying the seat.

Determinations of designated seating capacity under the amended definition should not cause manufacturers any real problems. If a manufacturer truly only intends to market a particular bench or split-bench seat for two occupants, he can and should make this obvious by the seat design, regardless of whether the total seat dimension is more than 50 inches or less than 50 inches. One simple way to do this is to install a permanent arm rest or console in the center portion of the seat.

I hope this response has clarified our position and will alleviate any problems you might have in making future determinations of proper designated seating capacity.

SINCERELY,

NISSAN MOTOR CO., LTD.

ENGINEERING OFFICE OF NORTH AMERICA

July 3, 1979

Frank A. Berndt Chief Counsel National Highway Traffic Safety Administration

Dear Mr. Berndt:

I am writing this letter to you to ask you for your interpretation concerning the 49 CFR Part 571, "Designated Seating Position," final rule in the April 19, 1979 Federal Register, Vol. 44, No. 77. Your earliest reply to the attached questions would be greatly appreciated.

Thank you for your cooperation in this matter. Hisakauz Murakami Staff Safety

cc: RALPH HITCHOCK; GUY HUNTER

Question 2.1 (a) General

Generally speaking, would the so-called trimmed surfaces within Area A in SAE J1100(a) include the slightly soft surface (for example, seat cushion surface, seat back surface and arm rest surface) which changes its form somewhat when an occupant is sitting?

Question 2.1 (b)

If your answer is "no" in Question 2.1 (a), please show me the detailed definitions of the trimmed surfaces (for example, body panel).

Question 2.2

Surface of the Arm-Rest

Would the surface of the arm rest be considered the trimmed surfaces within the Area A when the hip-room will be measured?

Arm Rest

Figure 2

(Graphics omitted)

Question 2.3

Surface of the Seat-Back

Would the surface of the seat-back on the wheel-house portion be considered the trimmed surfaces within Area A?

Portion of the seat-back

Figure 3

(Graphics omitted)

Question 2.4

Surface of the Outside Seat-Cushion Side

Would the surface of the outside seat-cushion side be considered the trimmed surfaces within Area A?

Outside seat-cushion side

Figure 4 Question 2.5

Surface of the Inside Seat-Cushion Side

Would the surface of the inside cushion side on the tunnel be considered the trimmed surfaces within Area A?

Inside seat-cushion side

Figure 5

(Graphics omitted)

NISSAN MOTOR CO. LTD. ENGINEERING OFFICE OF NORTH AMERICA

May 10, 1979

Guy Hunter Crashworthiness Division Office of Vehicle Safety Standards NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

Dear Mr. Hunter:

During my May 4th visit to your office, I requested your interpretation concerning the measurement procedure of the "Hip Room" with regard to SAE J 1100a, which was adopted in the 49 CFR Part 571, "Designated Seating Position". The final rule was issued in the April 19, 1979 Federal Register, Vol. 44, No. 77.

At that time, you suggested that I submit my questions, along with a letter, to your office for response.

I would, therefore, like to take this time to submit my questions to you and ask for your interpretation.

Thank you for your fine cooperation with regard to this particular matter. We look forward to hearing your interpretations in the near future.

Should any questions arise, please feel free to contact me at (201) 871-3555.

NISSAN MOTOR CO., LTD.

Hisakazu Murakami Staff, Safety

Q-1 The "X" plane through the SgRP

SAE J 1100a states the following as the definitions of the Three-Dimensional Reference System and the Hip-room:

ZERO "Y" PLANE - (Centerline body zero plane) is a vertical plane which passes through the longitudinal centerline of the vehicle.

ZERO "X" PLANE - Vertical body zero plane is a plane normal to the "Y" plane.

ZERO "Z" PLANE - Horizontal body zero plane is a plane normal to the "X" and "Y" planes.

W5-HIP ROOM-FRONT - The minimum dimension measured laterally between the trimmed surfaces on the "X" plane through the SgRP-front within 1.0 in (25 mm) below and 3.0 in (76 mm) above the SgRP-front and 3.0 in (76 mm) fore and aft of the SgRP-front.

W6-HIP ROOM-SECOND - Measured in the same matter as W5

The above-mentioned definitions are identical to those in SAE J 182a as shown in Fig. 1.

It is my understanding that the "X" plane through the SgRP (I think we should call this "X" plane the "Y-Z" plane through the SgRP, mathematically speaking) in W5 or W6 of SAE J 1100a is the one as shown in Fig. 2. Is my understanding correct?

Q-2 The measurement procedure of "Hip-room

Assuming that your answer to Q-1 is "yes", it would then be my understanding that there can be two (2) different ways of interpreting the measurement of W5 (or W6) as shown below.

(a) The case of emphasizing "the "X" plane through the SgRP"

In this case, W5 will be defined as follows, and the words of "and 3.0 in (76mm) fore and aft of the SgRP-front"will not be significant as shown in Fig. 3.

W5-HIP-ROOM - The minimum dimension measured laterally between the trimmed surfaces on the "X" plane through the SgRP-front within 1.0 in (25mm) below and 3.0 in (76mm) above the SgRP-front.

(b) The case of emphasizing "within 1.0 in . . . . aft of the SgRP-front"

In this case, W5 will be defined as follows, and the words of "through the SgRP-front" will not be significant as shown in Fig. 4.

W5-HIP-ROOM - The minimum dimension measured laterally between the trimmed surfaces on the "X" plane within 1.0 in (25mm) below and 3.0 in (76mm) above the SgRP-front and 3.0 in (76mm) fore and aft of the SgRP-front.

Which is correct, (a) or (b)?

FIG. 1

(Graphics omitted) FIG. 2

"X" plane through the SgRP

FIG. 3

FIG. 4 (Graphics omitted)