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Interpretation ID: 77-2.15

TYPE: INTERPRETATION-NHTSA

DATE: 04/18/77

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: AM General Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your oral request of March 28, 1977, for clarification of the language of S5.4.1 of Standard No. 217, Bus Window Retention and Release. In particular, you ask whether the long side of a rectangular roof exit is required to be parallel to the center line of a bus.

S5.4.1 requires that an exit provide "an opening large enough to admit unobstructed passage, keeping a major axis horizontal at all times, of an ellipsoid generated by rotating about its minor axis an ellipse having a major axis of 20 inches and a minor axis of 13 inches." Further, S5.2.1 of the standard states that a roof exit shall meet these requirements when the bus is overturned on either side. The requirement that the major axis be kept horizontal while the bus is on its side means that the major axis, and therefore the long side of the rectangular roof exit, would be parallel to the center line or the side wall of a bus.

Sincerely,