Interpretation ID: aiam2982
Manager
Engineering Services
Blue Bird Body Company
P.O. Box 937
Fort Valley
GA 31030;
Dear Mr. Milby: This responds to your November 29, 1978, letter asking severa questions about test procedures conducted in accordance with Standard No. 222, *School Bus Passenger Seating and Crash Protection*. Your questions concern the impact and contact area test requirements of the standard.; First, you suggest that the head and knee impact tests should b conducted with only one impact allowed per seat back. The standard states in S5.3.1: 'A surface area that has been contacted pursuant to an impact test need not meet further requirements contained in S5.3.' You apparently interpret 'surface area' to mean an entire seat back.; The purpose of the above-cited sentence in S5.3.1 is to assur manufacturers that the agency will not hit the test seat in the identical spot twice during compliance testing. However, it is permissible for several tests to be run on a seat as long as the test device does not impact the same specific area previously contacted by the device in an earlier test. This test method is appropriate because it approximates accident conditions. A seat is likely to be impacted more than once in an accident when the seat immediately behind it is occupied by three passengers. Accordingly, the agency will continue to run multiple tests on a seat back but will never impact the same 'surface area' more than once.; In your second question, you suggest that a test sequence i appropriate for contact area testing. The agency disagrees. The agency agrees that the head form and knee form impact tests are different tests for the reasons outlined in your letter. However, nothing in those reasons compels the agency to conclude that a test sequence would be appropriate for contact area testing. In an accident, the impact of children on a seat back may or may not be sequential in nature. Therefore, the existing test method, which permits the agency to sequence tests in any manner, closely reflects actual accident experiences. Accordingly, the agency will not adopt a specific sequence in its test procedures.; Sincerely, Frank Berndt, Chief Counsel