Interpretation ID: 1985-03.23

TYPE: INTERPRETATION-NHTSA

DATE: 07/24/85

FROM: AUTHOR UNAVAILABLE; Jeffrey R. Miller; NHTSA

TO: Thomas D. Turner -- Manager, Engineering Services, Blue Bird Body Co.

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Thomas D. Turner Manager Engineering Services Blue Bird Body Company P.O. Box 937 Fort Valley, Georgia 31030

This responds to your two letters to the National Highway Traffic Safety Administration (NHTSA) regarding Federal Motor Vehicle Safety Standard (FMVSS) No. 217, Bus Window Retention and Release. We apologize for the delay in responding to your letters.

Your December 6, 1984 letter asked about paragraph S5.4.1 of Standard No. 217 and the ellipsoid used to measure the unobstructed opening of a pushout window or other emergency exit. To simplify matters, I will refer to the illustration you attached with your letter. You asked whether you may rotate the ellipsoid in such a way that axis C-D may be horizontal instead of axis A-B.

By way of background information, I would like to explain that NHTSA does not pass approval on the compliance of any vehicle or equipment with a safety standard before the actual events that underlie certification. Under the National Traffic and Motor Vehicle Safety Act, the manufacturer is required to determine whether its vehicles and equipment comply with all applicable safety standards and regulations, and to certify its products in accordance with that determination. Therefore, the following statements only represent the agency's opinion based on the information provided in your letters.

Paragraph S5.4.1 of Standard No. 217 states that:

After the release mechanism has been operated, each push-out window or other emergency exit not required by S5.2.3 shall...be manually extendable by a single occupant to a position that provides 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.

Since the language of section S5.4.1 requires only that "a major axis" of the ellipsoid to be horizontal when the ellipsoid is passed through the emergency exit, you are not prohibited from positioning the ellipsoid with only a single major axis, such as C-D, horizontal. If there is unobstructed access of the ellipsoid through the opening, with major axis C-D horizontal, then the emergency exit meets the requirement of S5.4.1 as that section is written.

Even if the design of the exit would not violate S5.4.1, however, we urge you to ensure that the design would not complicate efforts of the passengers to use the emergency exit. It appears that the intent of the agency was for the plane generated by the major axes to be horizontal when the ellipsoid is passed through the exit. Otherwise, since a major axis of the ellipsoid will at all times be horizontal, no matter how the ellipsoid is passed, the benefit of such a requirement would be reduced. Further, the opening to the emergency exit could be significantly reduced when the only horizontal major axis is C-D.

The agency issued an opinion in April 1977, stating that S5.4.1 and S5.2.1 of Standard No. 217 require the long side of a rectangular roof exit to be parallel to the center line or the side wall of a bus. That opinion interpreted S5.4.1 as requiring the ellipsoid to be passed through the exit with more than one of its major axes horizontal. That interpretation relied on the intent of the standard, but not the language of S5.4.1.

This letter reconsiders the 1977 opinion and holds that the language of S5.4.1 requires only one major axis of the ellipsoid to be horizontal.

The two questions in your December 13, 1984 letter dealt with an outside release mechanism for pushout rear emergency windows. In a telephone call to this office on February 25, 1985, you said that the rear emergency pushout windows would be on school buses and buses other than school buses. You also asked whether an outside release mechanism may be installed on rear emergency doors on buses other than school buses.

Your first question was whether the following interpretation was correct:

FMVSS 217 does not require emergency exits to have outside release mechanisms, except for school bus emergency doors. Therefore, if we provide an outside handle to operate a pushout rear emergency window, it does not have to meet any force level or type of motion requirements.

You are correct that Standard No. 217 does not require emergency exits on school buses to have outside release mechanisms, with the exception in S5.3.3 for school bus emergency doors. We assume that there are release mechanisms for the pushout rear emergency windows located within the bus which meet all applicable requirements of Standard No. 217. If the emergency exit meets all applicable requirements of the standard, an outside release mechanism for a pushout rear emergency window, that is provided in addition to the release mechanisms required by the standard need not meet any force application and type of motion requirements.

Your second question was whether the outside handle on the pushout rear emergency window could be equipped with a key operated mechanism that disengages the handle from outside the bus for security purposes. The handle, even when locked from the outside, does not ever prevent operation of the window's release mechanisms from inside the bus. The answer to your question is yes. Standard No. 217 does not prohibit the type of handle you described when all applicable requirements of the standard can be met.

Our answers given above apply to outside release mechanisms on pushout rear emergency windows on school buses and buses other than school buses.

An outside release mechanism on rear emergency doors on buses other than school buses would likewise not have to meet any force application and type of motion requirements, if the emergency door meets all applicable requirements of Standard No. 217. The outside release mechanism can be equipped with the locking device you described, provided that Standard No. 217's requirements are met.

Sincerely,

Jeffrey R. Miller Chief Counsel

Mr. Frank Berndt Chief Counsel NHTSA 400 7th Street S.W. Washington, D.C. 20590

Reference: 49 CPR Part 517.217 Bus Window Retention and Release

Dear Mr. Berndt:

For purposes of FMVSS 217 the unobstructed opening a pushout window or other emergency exit, not required by S 5.2.3, must provide is defined as follows:

"...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."

When applying this requirement to a side pushout window with an adjacent seat, as shown in Figure 1 attached, we initially interpreted this requirement to mean the major axis A-B which is parallel to the longitudinal centerline of the vehicle as the major axis that must be kept horizontal. This interpretation required placing of the adjacent seat so that a 20 inch horizontal opening was maintained at the height the ellipsoid passed out the opening.

In certain body/capacity combinations, it requires uneven spacing of the seats to provide this clearance at pushout window locations required in certain states. Upon restudying the requirements, we have realized that the requirement is for a major axis to remain horizontal at all times. Since the ellipsoid is generated by rotating an ellipse about its minor axis, it is a circle in the top or bottom plan view and, therefore, has a multitude of major axes including A-B, C-D, E-F, as shown in the top view of Figure 1. Based on this, it is allowable to rotate the ellipsoid about axis C-D as shown in the side view of Figure 2 as long as axis C-D is kept horizontal at all times.

We feel rotating the ellipsoid about any major axis is allowed by the standard's wording as long as a major axis is kept horizontal, and that lt meets the intent of the standard and does not compromise safety in any way. We seek your confirmation of this interpretation as it will permit us to better meet our customer's needs by providing more flexibility in positioning seats adjacent to pushout windows.

Thank you for your consideration of this request and your early reply.

Very truly yours,

Thomas D. Turner Manager Engineering Services

dh/2057 Attachment

c: FMVSS 217 Correspondence File Jim Moorman David Carter

"INSERT GRAPHIC"

Mr. Frank Berndt Chief Counsel National Highway Traffic Safety Administration 400 7th Street S.W. Washington, D.C. 20590

Reference: 49 CFR Part 571.217 Bus Window Retention and Release

Dear Mr. Berndt:

The purpose of this letter is to make a correction in our December 6, 1984 letter discussing unobstructed opening requirements of FMVSS 217 and to request other interpretations regarding this standard. First, the reference in our December 6 letter should have been to 49 CFR Part 571.217 instead of 517.217. Please make this correction and accept our apology for any confusion this error may have caused.

Second, we request your confirmation of two interpretations regarding pushout rear window release mechanisms as follows:

1. FMVSS 217 does not require emergency exits to have outside release mechanisms, except for school bus emergency doors. Therefore, if we provide an outside handle to operate a pushout rear emergency window, it does not have to meet any force level or type of motion requirements.

2. Since an outside handle is not required on a pushout rear emergency window, we could provide a handle, with a key operated mechanism that allows the outside handle to be engaged or disengaged with the pushout window release mechanisms. Disengagement of the outside handle allows locking of the bus for security purposes but does not ever prevent operation of the release mechanism from inside the bus. We feel such a device therefore, meets the letter and intent of FMVSS 217.

Thank you for your consideration of this request.

Very truly yours, Thomas D. Turner Manager Engineering Services

fvc c: FMVSS 217 Correspondence File Jim Moorman David Carter