Interpretation ID: aiam3759
Specifications Chief
State Purchasing and General Services Commission
Lyndon Baines Johnson State Office Building
P.O. Box 13047 Capitol Station
Austin
TX 78711-3047;
Dear Mr. Martin: This responds to your letter to Mr. Kratzke of my staff seeking a interpretation of Standard No. 222, *School Bus Passenger Seating and Crash Protection* (49 CFR S 571.222). You indicated that you have been informed that section S5.1.2 of that standard requires that 90 percent of the total projected area of the seat backs on school buses must lie between a horizontal plane passing through the seating reference point and a parallel horizontal plane 20 inches above the seating reference point, and that this requirement appeared to be a geometric impossibility. The information you received about the requirements of section S5.1.2 is erroneous.; Section S5.1.2 does not specify any requirements for the *total projected area of the seat back. It simply mandates that the projected area of the *seat back between the two planes* you described at *at least* 90 percent of the width of the seat multiplied by 20. This requirement is very simple to satisfy geometrically by using a rectangle. If the seat back were rectangular, the area between the two planes would be 100 percent of the width of the seat multiplied by 20. The agency allows the width of the seat back to be multiplied by 90 percent so as to permit the use of seat backs which taper up at the top, but which still provide an adequate level of safety protection for the occupants.; The reason for specifying a requirement for the amount of area a sea back must have between these two planes is to ensure that 'compartmentalization' is not compromised. Compartmentalization is the term for protecting the occupants in the event of a crash by confining them within an area of sturdy, well-padded seats. If the seat back in front of a school bus occupant occupied less than 90 percent of the area between the two planes (the area that occupant is most likely to contact in case of a crash), the padded area to cushion the blow of that occupant might not be sufficient.; If you have any further questions or need further information on thi subject, please feel free to contact Steve Kratzke at this address and at (202) 246-2992.; Sincerely, Frank Berndt, Chief Counsel