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Interpretation ID: 23667.drn



    Mr. Mike J. Gower
    Trico Products (Europe) Ltd.
    High Street North
    Dunstable
    Beds. LU6 1UZ
    United Kingdom

    Dear Mr. Gower:

    This responds to your request for an interpretation of the correct "seating reference point" to use for a designated seating position when applying Standard No. 104, Windshield wiping and washing systems, to passenger cars. You ask whether the seating reference point is "that point which is in the rearmost position of the total seat travel and if the total seat movement envelope is trapezoidal in side view . . ., that this required point would also be the lowest?"

    Until April 8, 1993, the rearmost position of the driver's seat was required to be used for the determination of wiped areas A, B, and C in Standard No. 104. However, as explained below, this was changed by a 1993 final rule (44 FR 13021).

    S4.1.2 of Standard No. 104 specifies the area of the windshield that must be wiped by the vehicle's windshield wiping system. Paragraph S4.1.2.1 of the standard refers to SAE Recommended Practice J903a, May 1966, Passenger Car Windshield Wiper Systems. SAE J903a, paragraph 2.4(a), states that the wiped area on the windshield glazing surface is "defined and qualified" by the driver's seat in the rearmost position. It also states, "see Figure 1," which identifies "manikin H point with seat in rearmost position." Nonetheless, a March 9, 1993 final rule (copy enclosed), amended S3 of Standard No. 104 to substitute the term "seating reference point" for the term "manikin H point with seat in rearmost position." Specifically, S3 was amended to state: "The term seating reference point is substituted for the terms manikin H point with seat in the rearmost position and H point wherever any of these terms appear in any SAE Standard or SAE Recommended Practice referred to in this standard." Therefore, the term "seating reference point" replaces "manikin H point with seat in rearmost position" in Figure 1 of SAE J903a.

    Definitions for terms used in the Federal motor vehicle safety standards (one of which is Standard No. 104) are at 49 CFR 571.3, Definitions. "Seating reference point" (SgRP) is defined as:

      the unique design H-point, as defined in SAE J1100 (June 1984), which

      (a) Establishes the rearmost normal design driving or riding position of each designated seating position, which includes consideration of all modes of adjustment, horizontal, vertical, and tilt, in a vehicle;

      (b) Has X, Y and Z coordinates, as defined in SAE J1100 (June 1984), established relative to the designed vehicle structure;

      (c) Simulates the position of the pivot center of the human torso and thigh; and

      (d) Is the reference point employed to position the two-dimensional drafting template with the 95th percentile leg described in SAE J826 (May 1987), or, if the drafting template with the 95th percentile leg cannot be positioned in the seating position, is located with the seat in its most rearward adjustment position.

    The "Seating reference point" is not necessarily determined with the driver seat in its rearmost adjustment position. Instead, the SgRP may be located where the SAE J826 two-dimensional drafting template using a leg segment representative of a 95th percentile adult male is positioned. If a seat is provided with adjustment positions to accommodate persons larger than the 95th percentile adult male, any such adjustment positions would not affect the location of the SgRP. On the other hand, if the drafting template with the 95th percentile leg could not be positioned in the seat because its rearmost adjustment is too far forward, the SgRP must be located with the seat in its most rearward adjustment position.

    You could continue to use the rearmost position of the driver's seat in determining the wiped areas in Standard No. 104, although those areas may be slightly greater than if you used the seating reference point as interpreted above. This conservative approach could provide a margin of compliance to ensure that all vehicles produced will meet the Standard's requirements.

    You also asked whether the seating reference point was determined with the seat in its lowest adjustment point. SAE Jll00, June 1984, Motor Vehicle Dimensions (referenced above), paragraph 2.1, explains adjustments of the front seat position other than its rearmost normal driving position. It states that all other adjustable features, such as an adjustable steering wheel, and adjustable seat height, etc., shall be positioned in their normal driving position as specified by the manufacturer. Although a motor vehicle manufacturer may specify any seat height that would also be consistent with the fore-aft procedure for the seating reference point described above, you could use a variety of positions (full up, mid, full down, etc.) to determine the worst case (largest areas) for an additional margin of compliance.

    I hope this information is helpful. If you have any further questions, please contact Ms. Dorothy Nakama this address or at (202) 366-2992.

    Sincerely,

    John Womack
    Acting Chief Counsel

    Enclosure
    ref:104#571
    d.1/9/02