Interpretation ID: 9355
Specifications Engineer
Thomas Built Buses, Inc.
Post Office Box 2450
1408 Courtesy Road
High Point, NC 27261
Dear Ms Dawson:
This responds to your letter to Walter Myers of this office in which you posed two questions regarding interpretation of certain provisions of Federal Motor Vehicle Safety Standard (FMVSS) 217, Bus Window Retention and Release.
Your first question related to the definition of "daylight opening" found in the final rule amending FMVSS 217, dated November 2, 1992 (57 FR 49413) (hereinafter Final Rule). Specifically, you asked what constitutes an obstruction and how close does it have to be to the exit to be considered an obstruction.
The term "daylight opening" is defined in the Final Rule as "the maximum unobstructed opening of an emergency exit when viewed from a direction perpendicular to the plane of the opening." This refers to the total area of the opening, whether the door or window is open or closed. An obstruction in this context would include any obstacle or object that would block, obscure, or interfere with in any way that opening or any access thereto, as viewed from the middle aisle of the bus. For example, the seatback of a nearby seat that protrudes into the area perpendicular to the plane of the opening would constitute such an obstruction.
In your second question you referred to the current provisions of S5.2.3.1(b), FMVSS 217, which provides that a left-side emergency door must be located in the rear half of the bus passenger compartment. You then asked whether that requirement was changed in the Final Rule. The answer is yes.
S5.2.3.1, as amended in the Final Rule, provides manufacturers two options for the provision of school bus emergency exits, S5.2.3.1(a) (Option A) and S5.2.3.1(b) (Option B). Option A requires a rear emergency door and, in the sequence of choices for providing the additional emergency exit area, the first specifies a left side door that is required by S5.2.3.2(a)(2) to be located at the midpoint of the bus. Option B requires a left-side emergency door and a pushout rear window, but does not designate a specific location for them. Thus, the
locations of exits other than the left side door specified in S5.2.3.1(a)(2)(i) are left to the various design options of the manufacturers and their customers.
I hope this information will be of assistance to you. Should you have any further questions or seek additional information, please feel free to contact Walter Myers of my staff at this address or at (202) 366-2992.
Sincerely,
John Womack Acting Chief counsel
ref:217 d:4/1/94