Interpretation ID: aiam2805
Manager
Engineering Services
Blue Bird Body Company
P.O. Box 937
Fort Valley
GA 31030;
Dear Mr. Milby: This responds to your February 9, 1978, letter asking how to measur the head form contact area in Standard No. 222, *School Bus Passenger Seating and Crash Protection*.; In your first paragraph, you indicate that the National Highway Traffi Safety Administration (NHTSA) has allowed the knee form contact area measurement to be undertaken on or within a line 1 1/2 inches from the edge of the leg protection zone to ensure that the knee form will contact the entire surface. You ask that a similar line be established for the head protection zone contact areas.; As you know, the head form contact area requirements apply to mor areas than do the knee form contact area requirements. The knee form contact area requirements apply only to seat backs and the backs of restraining barriers. The head form contact area, on the other hand, includes anything falling within a specified zone which might include the sides or tops of seats. Therefore, it is impossible to create fictional lines around the outer edges of objects that fall within the head protection zone for purposes of testing the compliance of those objects with the requirements. The agency notes further that it never stated that it would test knee form contact area on or inside a line 1 1/2 inches from the edge of a seat back or restraining barrier. The agency did state that it would test in a manner that 'provides opportunity for the knee form to contact with the seat back or restraining barrier to the fullest extent possible.' That interpretation can also be applied to the head form contact area requirements.; Sincerely, Joseph J. Levin, Jr., Chief Counsel