Mr. Thomas D. Turner
Manager, Engineering Services
Blue Bird Body Company
P.O. Box 937
Fort Valley, GA 31030
Dear Mr. Turner:
This responds to your letter concerning Federal Motor Vehicle Safety Standard (FMVSS) No. 221, School Bus Body Joint Strength. You wish to confirm that portions of joints outside of the passenger compartment or that otherwise do not "enclose bus occupant space" are excluded from FMVSS No. 221. In particular, you ask about joints that are below the level of the floor line.
You described the portions of joints at issue as follows:
the top edge of the outside side panels on Blue Bird school buses start at the bottom of the side window openings and [the panels] continue down the side of the bus body, terminating with a bottom edge approximately 18 inches below the floor line. There are vertical joints between these panels and between these panels and other body components such as roof bows. The upper portions of these vertical joints are above the floor line while the lower portion of the same joint is below the floor line. [I]t is our understanding that the vertical joints between these side panels that lie above the floor line are subject to the joint strength requirements of FMVSS 221 (because the portions of the joined panels above the floor line serve to "enclose bus occupant space") while the portions of those joints below the floor line are excluded from the requirements (because the portions of the joined panels below the floor line do not "enclose bus occupant space").
You cite our April 26, 1976, and August 20, 1981, letters to Blue Bird and conclude from these letters that all joints below the "floor level" are exempt from FMVSS No. 221.
Generally speaking, joints below the floor line are excluded from FMVSS No. 221. However, in a letter of January 14, 1991, to Blue Bird, the agency clarified that the April 26, 1976, letter excluding joints below the floor line was predicated on the assumption that there is a body panel (i.e., a floor panel) at floor level that encloses the occupant space, and that is located between the occupant space and that portion of the bus excluded from the standard.Thus, the agency did not agree with Blue Birds view that stepwell-to-floor panel joints were below the floor level and excluded from FMVSS No. 221s joint strength requirements.
Accordingly, while we concur generally that joints below the floor line are excluded from FMVSS No. 221, we believe that there could be misinterpretation by a manufacturer as to whether a particular joint is considered such a joint. For example, we have enclosed two photographs on which we have superimposed the floor line on the bus exterior. The section of the circled joint above the line is subject to FMVSS No. 221; the section of the joint below the line is not. While we cannot provide you with a general response to your question, we will review more detailed information about a specific joint that might fall below the floor line of the bus to determine the applicability of FMVSS No. 221.
If you have any further questions, please feel free to contact Dorothy Nakama of my staff at this address or at (202) 366-2992. Should you choose to submit more detailed information for review, please submit it to Ms. Nakama.