49 CFR § 571.10 - Designation of seating positions.
(a) Application. This section applies to passenger cars, trucks, multipurpose passenger vehicles, and buses manufactured on or after September 1, 2010. However, paragraph (b) of this section does not apply to trucks and multipurpose passenger vehicles with a gross vehicle weight rating greater than 10,000 lbs, school buses, police vehicles as defined in S7 of Standard No. 208 (49 CFR 571.208), firefighting vehicles, ambulances, or motor homes. To determine the number of passenger seating positions in school buses, see S4.1 of Standard No. 222 (49 CFR 571.222).
(b) Number of designated seating positions. The formula for calculating the number of designated seating positions (N) for any seat location with a seating surface width greater than 330 mm (13 inches) is as follows:
(1) For seat locations with a seating surface width, as described in paragraph (c), of less than 1400 mm (55.2 inches): N = The greater of 1 or [seating surface width (in mm)/350] rounded down to the nearest whole number;
(2) For seat locations with a seating surface width, as described in paragraph (c), greater than or equal to 1400 mm (55.2 inches): N = No less than [seating surface width (in mm)/450] rounded down to the nearest whole number.
(c) Seating surface measurement.
(1) As used in this section, “seating surface” only includes the seat cushion and soft trim and excludes unpadded trim components such as a decorative seat shield, seat adjusters, or adjuster covers. As used in paragraphs (c)(1)(ii) and (iii) of this section, “outboard” and “inboard” are determined with respect to the measurement zone established in paragraph (c)(1)(i) of this section. As used in this section, “seating surface width” is the maximum horizontal width of a seating surface determined by the following procedure:
(i) Establish a measurement zone bounded by two vertical planes oriented perpendicular to the direction the seat is facing. One is located 150 mm (5.9 inches) behind the front leading surface of the seat and the other is located 250 mm (9.8 inches) behind the front leading surface of the seat. A measurement location within this zone is any vertical plane parallel to the planes establishing the boundary of the zone.
(ii) For each measurement location within the zone, establish vertical reference planes parallel to the direction the seat faces that intersect the most outboard point on each side of the seating surface at that measurement location. If outboard interior trim contacts the top surface of the seat cushion, establish another vertical plane parallel to the direction the seat faces that intersects the most inboard point of contact between outboard interior trim and the top surface of the seat cushion.
(iii) For measurement within the zone, measure horizontally between and perpendicular to the most inboard vertical reference planes established in (ii), as shown in Figure 1 (provided for illustration purposes).
(2) Adjacent seating surfaces are considered to form a single, continuous seating surface whose overall width is measured as specified in (c)(1) of this section, unless
(i) The seating surfaces are separated by:
(A) A fixed trimmed surface whose top surface is unpadded and that has a width not less than 140 mm (5.5 inches), as measured in each transverse vertical plane within that measurement zone, or
(B) A void whose cross section in each transverse vertical plane within that measurement zone is a rectangle that is not less than 140 mm (5.5 inches) wide and not less than 140 mm (5.5 inches) deep. The top edge of the cross section in any such plane is congruent with the transverse horizontal line that intersects the lowest point on the portion of the top profile of the seating surfaces that lie within that plane, or
(ii) Interior trim interrupts the measurement of the nominal hip room between adjacent seating surfaces, measured laterally along the “X” plane through the H-point. For purposes of this paragraph, the H-point is located using the SAE three-dimensional H-point machine per Society of Automotive Engineers (SAE) Surface Vehicle Standard J826, revised July 1995, “Devices for Use in Defining and Measuring Vehicle Seating Accommodation” (incorporated by reference, see section 571.5) with the legs and leg weights removed, or
(iii) The seating surfaces are adjacent outboard seats, and the lateral distance between any point on the seat cushion of one seat and any point on the seat cushion of the other seat is not less than 140 mm (5.5 inches).
(3) Folding, removable, and adjustable seats are measured in the configuration that results in the single largest maximum seating surface width.
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