Interpretation ID: 2809yy
Manager, Engineering Services
Blue Bird Body Company
P.O. Box 937
Fort Valley, GA 31030
Dear Mr. Turner:
This responds to your inquiry concerning the applicability of Federal Motor Vehicle Safety Standard No. 221; School Bus Body Joint Strength, to specific joints attaching the floor and stepwell of a school bus. Your letter included a blueprint of the floor and stepwell structure of a large school bus, and asked whether the joints joining the stepwell to the Number 1 and 2 floor sections of the bus are required to comply with the joint strength requirement of Standard No. 221.
Based on the information provided in your letter, I conclude that the joints attaching the floor sections to the stepwell are required to comply with the joint strength requirement contained in S5 of Standard 221. I also conclude that the joints in the stepwell are subject to that requirement.
As you are aware, S4 of the Standard defines "body panel" as:
"...a body component used on the exterior or interior surface to enclose the bus' occupant space."
S4 also defines "body panel joint" as:
"...the area of contact or close proximity between the edges of a body panel and another body component, excluding spaces designed for ventilation or another functional purpose, and excluding doors, windows, and maintenance access panels."
S5 of the Standard requires that body panel joints must comply with the strength requirement. The floor panels and stepwells of a bus are body components which come within the definition of body panel, as they serve to enclose the occupant space of the bus. The joints attaching the floor panels to the stepwell are body panel joints, since they represent the area of contact between the edges of a body panel (either a floor panel or the stepwell) and another body component (either the stepwell or a floor panel), and do not represent a space designed for ventilation or another functional purpose, or a door, window, or maintenance access panel.
I note that the joints attaching the stepwell to the floor sections are identical to, and in the same horizontal plane as, the joints used elsewhere in the floor assembly. I also note that the stepwell assembly described in your letter is also subject to the joint strength requirement. The various portions of the stepwell serve to enclose the occupant space, and are therefore body components which come within the definition of body panel. Therefore, the joints attaching those portions of the stepwell which enclose the occupant space are body panel joints subject to the requirements of the Standard.
Your letter argues that the stepwell joints are exempted from the definition of "body panel joint" by virtue of their being designed for another functional purpose. You do not, however, state the purpose. I disagree with this assertion. As noted above, S4 of the Standard exempts spaces designed for ventilation or another functional purpose from the definition of body panel joint. The agency's longstanding criterion for determining the applicability of this exemption has been whether the body panel joint in question is considered to have a function in enclosing the occupant space. See, March 18, 1977 letter to W.G. Milby (copy attached).
In this case, the stepwell clearly has the function of enclosing occupant space. I note that, by enclosing occupant space at a location which provides access to the front door, the stepwell occupies a critical location in relation to an important exit. Because of its location, the integrity of the stepwell in a crash is as important as the integrity of any other component comprising the floor.
In addition, you argue that the joints between the floor sections and the stepwell need not comply with S5 because they are below the level of the floor. This argument is based on your interpretation of an April 26, 1976 letter from this office to W.G. Milby at Blue Bird which states that components located entirely below the floor level are not subject to the Standard.
That letter did not intend to exclude from the Standard all portions of a bus located below the plane formed by the primary floorline of the bus. The exclusion of those portions below the floor level was instead predicated on the assumption that there is a body panel (i.e., a floor panel) at floor level which encloses the occupant space, and which is located between the occupant space and that portion of the bus excluded from the standard. I note that the floor level of a bus is not a single continuous plane; it is determined at any particular point by the plane of the panel that comprises the floor at that point. Therefore, I do not agree that the stepwell-to-floor panel joints indicated in your letter are below the floor level or are excluded from the standard's joint strength requirements.
I hope you have found this information useful. Please do not hesitate to contact J. Edward Glancy of my staff at (202) 366-2992 if you have any further questions.
Sincerely,
Paul Jackson Rice Chief Counsel
Enclosures ref:22l d:l/l4/9l