Interpretation ID: aiam2467
Manager of Engineering Services
School Bus Manufacturers Institute
5530 Wisconsin Avenue
Suite 1220
Washington
DC 20015;
Dear Mr. Crampton: This is in response to your letter of November 2, 1976, in which yo ask for an interpretation of the term 'absorbed' as it is used in Standard No. 222, *School Bus Passenger Seating and Crash Protection*. Further, you request that the NHTSA withdraw its earlier interpretation of the same term made on July 30, 1976, to Thomas Built Buses.; In your letter, you outline data showing that a seat may meet th energy absorbtion requirements of S5.1.3 when recoil energy is included, while failing those same requirements when recoil energy is subtracted from the total energy. You further argue that the NHTSA interpretation of July 30, 1976, which explained the subtraction of recoil energy, is at variance with the wording of the standard, because the standard does not explicitly require the subtraction of recoil energy and speaks only to the application of force upon the seat. Moreover, you suggest that plotting the recoil energy results in insufficient area under the force/deflection curve to meet S5.1.3. For these reasons, you request that the term 'absorbed' be defined as the total energy received by the seat without subtracting energy that is returned through recoil.; The NHTSA declines to adopt the interpretation that you suggest. Th dictionary definition of the term 'absorbed' is 'to receive without recoil.' This definition, when applied to energy absorbed by a seat, contemplates the subtraction of recoil energy in the computation of absorbed energy. The NHTSA intentionally chose the term 'absorbed' to denote exactly this meaning. Therefore, according to the common usage of the term 'absorbed,' the standard does require the subtraction of recoil energy even though those express words are never used.; Your assertion that plotting the recoil energy results in force/deflection curve that falls within the prohibited zones indicates a misunderstanding of the force/deflection zone requirements. The force deflection zone requirements (S5.1.3(a), S5.1.3(b), S5.1.4(a), and S5.1.4(b)) prescribe limits within which the seats must perform only during the force application phase of the test procedure.; Sincerely, Frank A. Berndt, Acting Chief Counsel