Interpretation ID: nht94-1.88

TYPE: Interpretation-NHTSA

DATE: March 21, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Lawrence P. White -- Acting Director, Bureau of Motor Vehicles, Dept. of Transportation, Commonwealth of Pennsylvania

TITLE: None

ATTACHMT: Attached to letter dated 12/13/93 from Lawrence P. White to Mary Versie (OCC-9479)

TEXT:

This responds to your letter of December 13, 1993, asking several questions concerning a recent amendment to Standard No. 217, Bus Emergency Exits and Window Retention and Release (57 FR 49413; November 2, 1992). Your questions and the response to each follows.

1. The effective date - is it the chassis manufacturer's date of completion, the final stage manufacturer's date of completion, or somewhere in between?

The effective date for the November 2 final rule is May 2, 1994. Only vehicles manufactured on or after the effective date of an applicable requirement in a Federal motor vehicle safety standard must comply with that requirement. If a vehicle is manufa ctured in two or more stages, the final stage manufacturer is required to certify that the vehicle complies with "the standards in effect on the date of manufacture of the incomplete vehicle, the date of final completion, or a date between those two date s." (49 CFR Part S568.6).

2. Based on the formula for emergency exit space, is the area of the front service door to be included? Does this mean on a vehicle of 60 to 77 passengers, the only additional requirements beyond the front and rear doors is a left side exit door?

The November 2 final rule requires additional emergency exit area (AEEA) for some buses. The amount, if any, of AEEA which must be provided is determined by subtracting the area of the front service door and either the area of the rear emergency door or the area of the side emergency door and the rear push-out window, depending on the configuration of the bus (S5.2.3.1). These are the minimum exits required on all buses. If AEEA is required, the first additional exit which must be installed is a left side emergency door (for a bus with a rear emergency door) or a right side emergency door (for a bus with a left side emergency door and a rear push- out window). The number of exits may vary for buses which carry the same number of passengers, because the amount of area credited for each exit is the area of daylight opening, and because different variations of types of exits are possible. However, in the regulatory evaluation for the final rule, the agency estimated that a bus would not be required to have a roof exit (the second type of additional exit required) unless the capacity was greater than 62 (for a bus with a rear emergency door) or 77 (for a bus with a left side emergency door and a rear push-out window).

3. The "clear aisle space" required for exit to the proposed side

emergency door, according to federal specifications, can be met with a flip-up type seat or a clear opening of 12", as measured from the back of the door forward. Are there any specifications, definitions, or descriptions provided as to what would be co nsidered a "flip seat"?

The November 2 final rule allowed a flip-up seat to be adjacent to a side emergency exit door "if the seat bottom pivots and automatically assumes and retains a vertical position when not in use, so that no portion of the seat bottom is within" the requi red 12 inch aisle to the exit (S5.4.2.1(a)(2)(ii)). The agency did not otherwise define a flip-up seat, nor did it include any performance requirements for these seats.

4. Also, there is concern regarding school buses that are equipped with the "flip seat" by the emergency door opening and the possibility of school children, either intentionally or accidently, unlatching the door latch mechanism. Are the door latch me chanisms to be equipped to help prevent this from occurring?

Standard No. 217 includes requirements for the type of motion and force required to release an emergency exit (S5.3.3). One of these requirements is that the notion to release a door must be upward from inside the bus (upward or pull-type for school bus es with a gross vehicle weight rating of 4,536 kilograms or less). This is intended to lessen the chance of a door accidently being opened, without unnecessarily making the exit more complicated to open in an emergency. In addition, warning alarms are required for door and window exits to notify the driver that the exit has been opened.

I hope you find this information helpful. If you have any other questions, please contact Walter Myers of my staff at this address or by phone at (202) 366-2992.