Interpretation ID: aiam1511
Project Engineer
The Adams & Westlake Company
1025 North Michigan Street
Elkhart
IN 46514;
Dear Mr. Hansing: This is in reply to your letter of April 16, 1974, concerning a interpretation of the requirements of Motor Vehicle Safety Standard No. 217, Bus Window Retention and Release' (49 CFR 571.217). You appear to ask whether bus windows containing tempered glass must meet the release requirements of paragraph S5.3.2 after (as well as before) the retention test required by S5.1 when the glass breaks during the retention test. You state that tempered glass, once broken, is easily removed from the entire lite by touch, implying that when this is the case there is no longer a need for any release mechanism to be further tested.; Paragraph S5.3.2 requires the release mechanism to meet specifie requirements both before and after the window retention test of S5.1 irrespective of the glazing material used in the lite. Consequently, release mechanisms for windows of tempered glass must conform to the requirements even though the glass may be broken during the retention test.; While your argument that the requirement seems unnecessary whe tempered glass is used is not without some basis, it is also quite likely, in our view, that bus passengers in a crash may be ignorant of the quality of tempered glass to which you refer and thus still attempt to operate the emergency exit using its release mechanism.; Yours truly, Richard B. Dyson, Assistant Chief Counsel