Interpretation ID: 21345.drn

Interpretation of Emergency Exits on
Double Decker Buses (Std. No. 217)
Frank Seales, Jr.
Chief Counsel
Kenneth N. Weinstein
Associate Administrator
for Safety Assurance

This responds to Mr. James Jones' request for an interpretation of the required emergency exit area in a double decker bus, as specified in Standard No. 217, Bus emergency exits and window retention and release. The buses at issue are over 4,536 kg (10,000 lb), and designed to seat 18 persons in the bottom tier (which is enclosed) and 32 persons in the top tier, which is open (i.e., has no roof, windows, or doors). In calculating the required exit area for each bus, NSA asks whether the calculation is "432 square centimeters x 50" (all the designated seating positions in the bus) or "432 square centimeters x 18" (only the designated seating positions in the bottom, enclosed tier of the bus). As explained below, the correct calculation is "432 square centimeters x 18."

It is my understanding that the buses at issue were not manufactured for sale in the US and information must be provided on how the buses can be modified to meet applicable FMVSSs, including Standard No. 217. The buses come in two models. The older model has a rear view window in the enclosed lower tier and the newer model is completely enclosed in the back in the lower tier. Mr. Luke Loy of your office has provided us with photographs with a view of each bus model from the front and from the back.

Standard No. 217 applies to "buses, except buses manufactured for the purpose of transporting persons under physical restraint." (See S3.) Among other purposes, Standard No. 217 is intended to "provide a means of readily accessible emergency egress." (See S2.) Standard No. 217 at S5.2.2.1 (provision of emergency exits for buses other than school buses) states in part: "Buses other than school buses shall provide unobstructed openings for emergency exit which collectively amount, in total square centimeters, to at least 432 times the number of designated seating positions on the bus."

For purposes of this interpretation, it will be assumed that the double decker bus manufacturer has certified each vehicle as a "bus." I have carefully reviewed the rulemaking history of Standard No. 217. Nowhere (in any of the preambles or regulatory texts) is the applicability of S5.2.2.1 (or any other Standard No. 217 provision) to double decker buses discussed. I therefore determine that Standard No. 217 was written to address emergency escape from the enclosed areas of buses. Applying this principle to the double decker bus with the open top tier, the required exit area would be calculated by multiplying 432 square centimeters x 18 positions. The 18 positions represent the number of designated seating positions in the bottom, enclosed area of the bus.

Please note that this interpretation reflects consideration of the purposes underlying Standard No. 217 generally, and S5.2.2.1 in particular. Standard No. 217 was promulgated to provide a means of readily accessible emergency egress from a bus. In order to accomplish this, the Standard at S5.2.2.1 specifies, in total square centimeters, the unobstructed openings for emergency exit that is based in part on the number of designated seating positions on the bus.

I also note that S5.2.2.2 (applicable to buses over 4,536 kg (10,000 lb)) states in part: "When the bus configuration precludes installation of an accessible rear exit, a roof exit that meets the requirements of S5.3 through S5.5 when the bus is overturned on either side, with the occupant standing facing the exit, shall be provided in the rear half of the bus." Judging from the photographs, the configuration of each double decker bus model may "preclude[s] installation of an accessible rear exit." If so, installation of a roof exit may pose problems not seen on an enclosed bus. Since the bus is double decker, passengers on the top tier may be expected to walk on the roof exit. The roof exit on the double decker bus therefore may have to be strong enough to support more than one person walking on it. So that the roof exit is available for use in an emergency, means should be provided to ensure that no seating position is on or above it.

I hope this information is helpful. If you have any further questions, please contact Dorothy Nakama at 6-2992.

ref:217
d.4/6/2000