Interpretation ID: 24061version2
Mr. Jim Freibirger
Senior Staff Engineer
Thomas Built Buses
1408 Courtesy Road
High Point, NC 27260
Dear Mr. Freibirger:
This responds to your letter requesting an interpretation of Federal Motor Vehicle Safety Standard No. 221, School Bus Body Joint Strength. The joint at issue is formed in part by a steel "wire trim cover" that covers a wiring harness just above the window header. You ask whether the joint is a body panel joint under amendments to Standard No. 221 that become effective January 1, 2003. (See 66 FR 64358, December 13, 2001, copy enclosed.) As explained below, the answer is yes.
The joint at issue will be a body panel joint under the standard.[1] "Body panel joint" will mean: "the area of contact or close proximity between the edges of a body panel and another body component, including but not limited to floor panels, and body panels made of composite materials such as plastic or plywood, excluding trim and decorative parts which do not contribute to the strength of the bus body, members such as rub rails which are entirely outside of body panels, ventilation panels, components provided for functional purposes, and engine access covers." The standard will require that (S5.1): "Except as provided in S5.2, each body panel joint, including small, curved, and complex joints, when tested in accordance with the procedure of S6, shall hold the body panel to the member to which it is joined when subjected to a force of 60 percent of the tensile strength of the weakest joined body panel determined pursuant to S6.2." The exceptions specified in S5.2 will be:
(a) Any interior maintenance access panel or joint which lies forward of the passenger compartment.
(b) Any interior maintenance access panel within the passenger compartment that does not exceed 305 mm [12 inches] when measured across any two points diametrically on opposite sides of the opening.
(c) Trim and decorative parts which do not contribute to strength of the joint, support members such as rub rails which are entirely outside of body panels, doors and windows, ventilation panels, and engine access covers.
The joint in question would not fall within any of the exceptions specified in S5.2. It is not a maintenance access panel (S5.2(a) and (b)). The amendments include a definition of "maintenance access panel" which is: "a body panel which must be moved or removed to provide access to one or more serviceable components." "Serviceable component" is defined as: "any part of the bus, of either a mechanical or electrical nature, which is explicitly identified by the bus chassis and/or body manufacturer in the owners manual or factory service manual as requiring routine maintenance actions at intervals of one year or less. Tubing, wires and harnesses are considered to be serviceable components only at their attachments." Under these definitions, your body panel joint cannot be considered a maintenance access panel because it would be covering the entire wiring harness, not just the attachment points. Further, the joint is not comprised of a trim and decorative part that does not contribute to the strength of the joint (S5.2(c)). Your joint is a structural joint because its steel part forms part of the integral inner shell. That is, your joint forms part of the steel structure that attaches to the roof bow, and contributes to the strength of the entire bus body.
We further note that in the event of a crash, shearing forces on a steel joint could result in jagged edges to the steel, which may cause serious injury to children who might contact the edges. You suggest that the joint in question should be excluded because in an August 31, 2000 letter to Blue Bird Body Company, NHTSA excluded a wire trim part. The wire trim part that we addressed in our August 2000 letter differs from the body panel joint at issue. Both your joint and Blue Birds trim are placed above the school bus window. However, with regard to Blue Birds trim, we determined that "plastic wire trim parts at issue do not contribute to the structural integrity or the joint strength of the bus." The Blue Bird trim also was not part of the integral inner shell. In contrast, Thomas Builts joint is a structural joint because it forms part of the integral inner shell. Since your joint forms part of the structure that attaches to the roof bow, and contributes to the strength of the entire bus body, it is a "body panel joint" within the meaning of Standard No. 221.
I hope this information is helpful. If you have any further questions, please feel free to contact Dorothy Nakama of my staff at this address or at (202) 366-2992.
Sincerely,
John Womack
Acting Chief Counsel
Enclosures
ref:221
d.6/25/02
[1] Note that we also consider the joint in question to be a body panel joint under the existing standard. See September 2, 1976 letter to the Blue Bird Body Company (copy enclosed) pertaining to "the area of contact between headlining panels and the header over the windows."