United States Department of TransportationInterpretation ID: 2509y
Salem Vent International, Inc.
P.O. Box 885
Salem, VA 24153
Dear Mr. Kelly:
This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard (FMVSS) No. 217; Bus Window Retention and Release as it applies to roof exits. You asked four specific questions which I have addressed below.
First, you asked for confirmation that the only specification in Standard No. 217 concerning the size of roof exits is the requirement that the exit be able to accommodate an ellipsoid with a major axis of 20 inches and a minor axis of 13 inches pushed horizontally through the exit opening. Your understanding is not entirely correct. The ellipsoid requirement to which you refer, set forth in S5.4.1 of Standard No. 217, is the only provision in the standard that specifies a minimum size requirement for roof exit openings. Although there is no maximum size limit, you should be aware that S5.2 of Standard No. 217 provides that, in determining the total unobstructed openings for emergency exit provided by a bus, no emergency exit, regardless of its area shall be credited with more than 536 square inches of the total area requirement. Thus, if a roof exit is larger than 536 square inches, only 536 square inches will be counted for the exit in determining whether the bus complies with the unobstructed openings requirement of S5.2 of Standard No. 217.
Second, you asked for confirmation that Standard No. 217 does not permit the use of escape hatches or ventilators in the roof of school buses as a substitute for any of the emergency exits required on school buses by S5.2.3 of Standard No. 217. This understanding is correct. Additionally, you should be aware that the agency has a longstanding position that any emergency exits, including any roof exits, installed on a school bus in addition to the emergency exits required by S5.2.3 must conform to the requirements of Standard No. 217 for emergency exits installed on buses other than school buses. See the enclosed July 6, 1979 interpretation to Robert Kurre on this issue. Third, you asked for confirmation that Standard No. 217 permits the use of roof exits as a substitute for the rear exit door on buses other than school buses. This statement is not entirely correct. S5.2.1 of Standard No. 217 requires the use of a rear exit door on all non-school buses with a GVWR of more than 10,000 lbs., except where the configuration of the bus precludes the installation of an accessible rear exit. In that case, S5.2.1 requires the installation of a roof exit in the rear half of the bus in lieu of the rear exit. This substitution of a roof exit for a rear exit door is allowed only where the bus design precludes the use of a rear exit (such as on rear-engine buses). It is not an option allowing the substitution of a roof exit for the rear door in any design.
Fourth, you asked whether the addition of more than one roof exit on a non-school bus would allow a manufacturer to delete any other required exits in addition to the rear door. It is possible that increasing the total exit space on the bus by adding roof exits could enable a manufacturer to reduce the number or size of other emergency exits on the bus and still comply with the unobstructed openings requirement of S5.2. You should be aware that exit space provided by roof exits is not counted in determining compliance with the requirement in S5.2 that 40 percent of the total unobstructed openings be located on each side of the bus. Whether this substitution of additional roof exits could be made on any particular non-school bus would depend upon whether the bus complied with the exit space and location requirements of S5.2.1 (if the bus has a GVWR of more than 10,000 pounds) and the applicable requirements of S5.2.2 (if the bus has a GVWR of 10,000 pounds or less).
I hope you have found this information helpful. Please do not hesitate to contact David Greenburg of my staff at (202) 366-2992 if you have any further questions or need additional information.
Sincerely,
Stephen P. Wood Acting Chief Counsel
Enclosure
/ref:217 d:5/30/90