Passenger: Emergency Exits
14 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.
Sources: 49 CFR 571.217
What you need to know
FMVSS 217 S2 names both: keeping people inside during a crash, which is the window retention half, and letting them out afterwards, which is the emergency exit half.
The two pull in opposite directions, which is why the standard sets both retention strength and release force. Those are the two stated purposes of the standard.
The purpose of this standard is to minimize the likelihood of occupants being thrown from the bus and to provide a means of readily accessible emergency egress.
49 CFR 571.217
FMVSS 217 S3 excepts buses built to transport persons under physical restraint.
Easily openable exits would defeat the purpose of such a vehicle.
This standard applies to buses, except buses manufactured for the purpose of transporting persons under physical restraint.
49 CFR 571.217
FMVSS 217 S5.2.2.1 scales the requirement with capacity: 432 square centimetres times the number of designated seating positions.
More people means more opening needed to get them out.
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.
49 CFR 571.217
FMVSS 217 S5.2.2.1 requires at least 40 percent per side, so neither side can be left short.
A bus resting on one side after a rollover must still have usable exits on the side now facing up. None of the figures offered is the one the rule gives.
At least 40 percent of the total required area of unobstructed openings, computed in the above manner, shall be provided on each side of a bus.
49 CFR 571.217
FMVSS 217 S5.2.2.1 caps the credit per exit.
Without it a manufacturer could meet the area figure with one huge opening, which is useless if that is the side the bus lands on or the end that is crushed. Several exits spread the escape routes around the bus.
no emergency exit, regardless of its area, shall be credited with more than 3,458 square centimeters of the total area requirement
49 CFR 571.217
FMVSS 217 S5.2.2.2 requires side exits plus at least one rear exit.
Where the configuration precludes an accessible rear exit, a roof exit in the rear half of the bus may be substituted.
Buses with a GVWR of more than 10,000 pounds shall meet the unobstructed openings requirements in S5.2.2.1 by providing side exits and at least one rear exit
49 CFR 571.217
FMVSS 217 S5.2.2.2 requires the rear exit to work upright and with the bus on either side.
A crash rarely leaves the bus upright, so an exit that only opens level is not an emergency exit. The occupant is assumed to be standing facing the exit.
The rear exit shall meet the requirements of S5.3 through S5.5 when the bus is upright and when the bus is overturned on either side, with the occupant standing facing the exit.
49 CFR 571.217
FMVSS 217 S5.1 defines retention by whether a 4-inch sphere can pass under 5 pounds of force, with the test running until a force of 1,200 pounds is reached or the other listed events occur.
The concern is a person being thrown through the gap. The requirement holds until the stated force and deflection limits are reached. The test applies a 5 pound force, and holds until the stated limits are reached. None of the figures offered is the one the rule gives.
each piece of window glazing and each surrounding window frame when tested in accordance with the procedure in S5.1.1 under the conditions of S6.1 through S6.3, shall be retained by its surrounding structure in a manner that prevents the formation of any opening large enough to admit the passage of a 4-inch diameter sphere under a force, including the weight of the sphere, of 5 pounds
49 CFR 571.217
FMVSS 217 S5.1.2 exempts windows under 8 inches in minimum dimension, because an occupant could not pass through such an opening anyway.
Measured as the minimum surface dimension.
The requirements of this standard do not apply to a window whose minimum surface dimension measured through the center of its area is less than 8 inches.
49 CFR 571.217
FMVSS 217 S5.4.1 uses a 50 cm by 33 cm ellipsoid passed with its major axis horizontal, which approximates a person's shoulders.
It must be openable by a single occupant. The ellipsoid must pass with its major axis horizontal.
allow manual opening 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 50 centimeters and a minor axis of 33 centimeters
49 CFR 571.217
FMVSS 217 S5.2.1.1 allows one side door per three seating positions as a way of meeting the openings requirement.
It suits a vehicle laid out with many doors rather than few large exits.
A bus with GVWR of more than 10,000 pounds may satisfy the unobstructed openings requirement by providing at least one side door for each three passenger seating positions in the vehicle.
49 CFR 571.217
FMVSS 217 S5.5.1 requires the instructions within 16 cm of the mechanism.
Note school buses use 15 cm under S5.5.3(b), so the two figures differ slightly by bus type. They must cover every motion needed to unlatch and open the exit.
each emergency exit door shall have the designation “Emergency Door” or “Emergency Exit,” and every other emergency exit shall have the designation “Emergency Exit” followed by concise operating instructions describing each motion necessary to unlatch and open the exit, located within 16 centimeters of the release mechanism.
49 CFR 571.217
FMVSS 217 S5.5.2 sets a demanding and specific test: night lighting only, 20/40 vision, three named positions, and legible from each while the other two are occupied.
Markings must work when the bus is full and dark. The marking must be legible from the adjacent seat, the next seat along and the nearest aisle position. It must be legible to 20/40 corrected vision from the adjacent seat, the next seat along and the nearest aisle position.
each marking shall be legible, when the only source of light is the normal nighttime illumination of the bus interior, to occupants having corrected visual acuity of 20/40 (Snellen ratio) seated in the adjacent seat, seated in the seat directly adjoining the adjacent seat, and standing in the aisle location that is closest to that adjacent seat.
49 CFR 571.217
FMVSS 217 S5.5.2.1 tests it from the floor, backs down, which is the position of someone in a bus that has rolled.
The test imagines the situation in which a roof exit is actually used. The occupant is assumed to be opposite the roof exit.
If the exit has no adjacent seat, the marking must meet the legibility requirements of S5.5.2 for occupants standing in the aisle location nearest to the emergency exit, except for a roof exit, which must meet the legibility requirements for occupants positioned with their backs against the floor opposite the roof exit.
49 CFR 571.217
Check yourself
- The two stated purposes of the standard are ______.
- What are the buses to which the exit standard does not apply?
- What is the method for calculating the required emergency exit opening area?
- What is required for the exit opening area to be distributed across your bus?
- What is the reason a single large exit is capped at 3,458 square centimetres?
- What are the exits your bus over 10,000 pounds GVWR must provide?
- What are the positions in which your bus's rear exit must remain usable?
- What is the window retention test on your bus measuring?
- What are the windows outside the federal window retention requirements?
- What is the size of opening an emergency exit must provide once released?
- What is the alternative route to compliance for a bus over 10,000 pounds GVWR?
- What is required to accompany the emergency exit designation on a non-school bus?
- What are the conditions under which an emergency exit marking must stay legible?
- What is the method for testing roof exit marking legibility on a non-school bus?
Answers are in the practice test for this topic.