Interpretation ID: 77-5.21

TYPE: INTERPRETATION-NHTSA

DATE: 12/30/77

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: W. G. Milby

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your November 14, 1977, letter asking about the applicability of the requirements of Standard 217, Bus Window Retention and Release, to roof exits which use lexan or other glazing materials as part of their structure.

You first ask whether these exits would be required to comply with the standard's window retention test. Section S5.1 of the standard requires that each piece of window glazing and each surrounding window frame comply with the requirements of the window retention test. Since the lexan to which you refer is glazing material, a structure using such material would be required to comply with the window retention test.

In a second question, you ask whether this type of exit can employ a release mechanism that consists of a gasket filler strip. This gasket releases the exit when pulled, by a single force, in a direction perpendicular to the exit. Since the application of force required to release the exit is in the proper direction as established by S5.3.2 of the standard, the exit would appear to comply with the exit release requirements as long as the release mechanism is within the correct force application zone and requires the proper amount of energy to effect its release.