Interpretation ID: aiam2512
Project Engineer
Ward School Bus Mfg.
Inc.
P. O. Box 849
Highway 65 South
Conway
AR 72032;
Dear Mr. Titsworth: This responds to your December 7, 1976 and January 8, 1977, question whether 53 described intersections of bus body components qualify as 'body panel joints' subject to the requirements of Standard No. 221, *School Bus Body Joint Strength*. This also responds to your question whether the seating reference point in Standard No. 222, *School Bus Passenger Seating and Crash Protection*, can be located using nominal seat cushion deflection.; The terms which establish the applicability of the requirements of th standard to a particular section of a school bus body are defined in S4 of the standard. Read together, they establish the following test. If the edge of a surface component (made of homogeneous material) in a bus that encloses the bus' occupant space comes into contact or close proximity with any other body component, the requirements of S5 apply, unless the area in question is designed for ventilation or another functional purpose or is a door, window, or maintenance access panel. Applying this test to the 53 intersections of bus body components you describe, it appears that the areas corresponding to the following numbered paragraphs of your letter are bus body joints and therefore must meet the 60-percent joint strength requirements: 1 through 34, 36, 37, 39, 42, 44, 45, 46, 51. Additionally the joint described in your January 8, 1977, submission must comply with the standard.; The illustration accompanying paragraph 16 shows a second joint betwee a door post and exterior trim panel with the notation that this joint is 'Not Required To Meet Std.' The agency concludes that this joint also must meet the requirements of the standard, because it is a connection of a body component with a body panel that encloses occupant space.; The lower skirt section described in paragraph 35 is not a body pane that encloses occupant space, because it is located entirely below the level of the floor line and, therefore, is excluded from the standard's requirements.; In the control console area, the interior side panel described i paragraph 38 and the shoulder cap (wire cover) described in paragraph 43 are considered maintenance access panels, whose joining with the bus body is excluded from the requirements only if a wire is installed behind them.; The turn signal housings described in paragraphs 40 and 41 are no considered to have a function in enclosing the occupant space and are therefore not considered body components for purposes of the requirements.; The front and rear headers described in paragraphs 47 and 48 ar considered primarily structural and have only an incidental role in enclosing the occupant space and, therefore, are not considered 'body panels' for purposes of the requirements.; The rubrail described in paragraph 49 is not considered to have function in enclosing the occupant space and, therefore, is not considered a body component for purposes of the requirements. For purposes of testing the complex joints to which it is fastened, it should be modified as necessary to prevent it from affecting testing of the underlying joint.; Because the plywood described in paragraph 50 is attached to a floo panel and is only added to some buses for insulation purposes, it is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.; The NHTSA concludes that parts A, E, and F of paragraph 52 describ joints between maintenance access panels and the bus body. The heater ducts in parts B, C, and D are the type of ventilation space that is not subject to requirements for joint strength.; In response to your question concerning the effect of seat cushio deflection on the location of the seating reference point, the NHTSA has determined that the definition of seating reference point contemplates some deflection of seat cushions to simulate compression of padding material under the weight of a human torso and thigh. As noted in the preamble of the second proposal for a school bus seating standard (39 FR 27585, July 30, 1974), 'It can be seen that the manufacturer's freedom to locate the point is sharply restricted by the definition which specifies that it actually simulate the position of the pivot center of the human torso and thigh, following SAE placement procedures.' However, since the seating reference point is an approximation of the pivot center, the NHTSA permits the manufacturer to locate the point based upon nominal seat cushion deflection.; Sincerely, Frank A. Berndt, Acting Chief Counsel