571.217—Standard No. 217; Bus emergency exits and window retention and release.

S1. Scope. This standard establishes requirements for the retention of windows other than windshields in buses, and establishes operating forces, opening dimensions, and markings for bus emergency exits.
S2. Purpose. 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.
S3. Application. This standard applies to buses, except buses manufactured for the purpose of transporting persons under physical restraint.
S4. Definitions. Adjacent seat means a designated seating position located so that some portion of its occupant space is not more than 10 inches from an emergency exit, for a distance of at least 15 inches measured horizontally and parallel to the exit.
Daylight opening means the maximum unobstructed opening of an emergency exit when viewed from a direction perpendicular to the plane of the opening.
Mid-point of the passenger compartment means any point on a vertical transverse plane bisecting the vehicle longitudinal centerline that extends between the two vertical transverse planes which define the foremost and rearmost limits of the passenger compartment.
Occupant space means the space directly above the seat and footwell, bounded vertically by the ceiling and horizontally by the normally positioned seat back and the nearest obstruction of occupant motion in the direction the seat faces.
Passenger compartment means space within the school bus interior that is between a vertical transverse plane located 76 centimeters in front of the forwardmost passenger seating reference point and a vertical transverse plane tangent to the rear interior wall of the bus at the vehicle centerline.
Post and roof bow panel space means the area between two adjacent post and roof bows.
Push-out window means a vehicle window designed to open outward to provide for emergency egress.
Sliding window means a bus window designed to open by moving vertically or horizontally to provide emergency egress.
Wheelchair means a wheeled seat frame for the support and conveyance of a physically disabled person, comprising at least a frame, seat, and wheels.
Wheelchair securement anchorage means the provision for transferring wheelchair securement device loads to the vehicle structure.
Wheelchair securement device means a strap, webbing or other device used for securing a wheelchair to the school bus, including all necessary buckles and other fasteners.
S5. Requirements.
S5.1Window retention. Except as provided in S5.1.2, 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 until any one of the following events occurs:
S5.1.1An increasing force shall be applied to the window glazing through the head form specified in Figure 4, outward and perpendicular to the undisturbed inside surface at the center of the area of each sheet of window glazing, with a head form travel of 2 inches per minute.
S5.1.2The 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.
S5.2Provision of emergency exits.
S5.2.1Buses other than school buses shall meet the requirements of either S5.2.2 or S5.2.3. School buses shall meet the requirements of S5.2.3.
S5.2.1.1A 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.
S5.2.2Buses other than school buses.
S5.2.2.1Buses 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. 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. However, in determining the total unobstructed openings provided by a bus, no emergency exit, regardless of its area, shall be credited with more than 3,458 square centimeters of the total area requirement.
S5.2.2.2Buses with GVWR of more than 10,000 pounds. 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 that conforms to S5.3 through S5.5. 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. 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.
S5.2.2.3Buses with GVWR of 10,000 pounds or less. Buses other than school buses with GVWR of 10,000 pounds or less may meet the unobstructed openings requirement in S5.2.2.1 by providing:
S5.2.3School buses. Except as provided in S5.2.3.4, each school bus shall comply with S5.2.3.1 through S5.2.3.3.
S5.2.3.1.Each school bus shall be equipped with the exits specified in either S5.2.3.1(a) or S5.2.3.1(b), chosen at the option of the manufacturer.
Table 1
Seating capacity Additional exits required *
1-45 None.
46-62 1 left side exit door or 2 exit windows.
63-70 1 left side exit door or 2 exit windows, and 1 roof exit.
71 and above 1 left side exit door or 2 exit windows, and 1 roof exit, and any combination of door, roof, or windows such that the total capacity credit specified in Table 3 for these exits, plus 70, is greater than the seating capacity of the bus.
* Side emergency exit doors must meet the requirements of S5.2.3.2(a), emergency roof exits must meet the requirements of S5.2.3.2(b), emergency window exits must meet the requirements of S5.2.3.2(c).
Table 2
Seating capacity Additional exits required *
1-57 None.
58-74 1 right side exit door or 2 exit windows.
75-82 1 right side exit door or 2 exit windows, and 1 roof exit.
Code of Federal Regulations 945
83 and above 1 right side exit door or 2 windows, and 1 roof exit, and any combination of door, roof, or windows such that the total capacity credit specified in Table 3 for these exits plus 82 is greater than the capacity of the bus.
* Side emergency exit doors must meet the requirements of S5.2.3.2(a), emergency roof exits must meet the requirements of S5.2.3.2(b), emergency window exits must meet the requirements of S5.2.3.2(c).
Table 3
Exit Type Capacity Credit
Side Door 16
Window 8
Roof Exit 8
S5.2.3.2All emergency exits required by S5.2.3.1(a) and S5.2.3.1(b) shall meet the following criteria:
S5.2.3.3 The engine starting system of a bus shall not operate if any emergency exit is locked from either inside or outside the bus. For purposes of this requirement, “locked” means that the release mechanism cannot be activated and the exit opened by a person at the exit without a special device such as a key or special information such as a combination.
S5.2.3.4Each school bus manufactured before September 1, 1994 may, at the manufacturer's option, comply with either S5.2.3.4(a) or S5.2.3.4(b) instead of S5.2.3.1 through S5.2.3.3.
S5.3Emergency exit release.
S5.3.1Each emergency exit not required by S5.2.3 shall be releasable by operating one or two mechanisms located within the regions specified in Figure 1, Figure 2, or Figure 3. The lower edge of the region in Figure 1, and Region B in Figure 2, shall be located 13 centimeters above the adjacent seat, or 5 centimeters above the arm rest, if any, whichever is higher.
S5.3.2When tested under the conditions of S6., both before and after the window retention test required by S5.1, each emergency exit not required by S5.2.3 shall allow manual release of the exit by a single occupant using force applications each of which conforms, at the option of the manufacturer, either to S5.3.2 (a) or (b) of this section. Each exit shall have not more than two release mechanisms. In the case of exits with one release mechanism, the mechanism shall require two force applications to release the exit. In the case of exits with two release mechanisms, each mechanism shall require one force application to release the exit. At least one of the force applications for each exit shall differ from the direction of the initial motion to open the exit by not less than 90° and no more than 180°.
S5.3.3 School bus emergency exit release.
S5.3.3.1When tested under the conditions of S6., both before and after the window retention test required by S5.1, each school bus emergency exit door shall allow manual release of the door by a single person, from both inside and outside the passenger compartment, using a force application that conforms to S5.3.3.1 (a) through (c) of this section, except a school bus with a GVWR of 10,000 pounds or less is not required to conform to S5.3.3.1 (a). The release mechanism shall operate without the use of remote controls or tools, and notwithstanding any failure of the vehicle's power system. When the release mechanism is not in the position that causes an emergency exit door to be closed and the vehicle's ignition is in the “on” position, a continuous warning sound shall be audible at the driver's seating position and in the vicinity of the emergency exit door.
S5.3.3.2When tested under the conditions of S6., both before and after the window retention test required by S5.1, each school bus emergency exit window shall allow manual release of the exit by a single person, from inside the passenger compartment, using not more than two release mechanisms located in specified low-force or high-force regions (at the option of the manufacturer) with force applications and types of motions that conform to either S5.3.3.2 (a) or (b) of this section. In the case of windows with one release mechanism, the mechanism shall require two force applications to release the exit. In the case of windows with two release mechanisms, each mechanism shall require one application to release the exit. At least one of the force applications for each window shall differ from the direction of the initial motion to open the exit by no less than 90° and no more than 180°. Each release mechanism shall operate without the use of remote controls or tools, and notwithstanding any failure of the vehicle's power system. When a release mechanism is open and the vehicle's ignition is in the “on” position, a continuous warning shall be audible at the drivers seating position and in the vicinity of that emergency exit.
S5.3.3.3When tested under the conditions of S6., both before and after the window retention test required by S5.1, each school bus emergency roof exit shall allow manual release of the exit by a single person from both inside and outside the passenger compartment, using not more than two release mechanisms located at specified low-force or high-force regions (at the option of the manufacturer) with force applications and types of motions that conform either to S5.3.3.3 (a) or (b) of this section. In the case of roof exits with one release mechanism, the mechanism shall require two force applications to release the exit. In the case of roof exits with two release mechanisms, each mechanism shall require one application to release the exit. At least one of the force applications for each roof exit shall differ from the direction of the initial push-out motion of the exit by no less than 90° and no more than 180°.
S5.4Emergency exit opening.
S5.4.1After the release mechanism has been operated, each emergency exit not required by S5.2.3 shall, under the conditions of S6., both before and after the window retention test required by S5.1, using the reach distances and corresponding force levels specified in S5.3.2, 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.
S5.4.2School bus emergency exit opening.
S5.4.2.1School buses with a GVWR of more than 10,000 pounds.
S5.4.2.2School buses with a GVWR of 10,000 pounds or less. A school bus with a GVWR of 10,000 pounds or less shall conform to all the provisions of S5.4.2, except that the parallelepiped dimension for the opening of the rear emergency door or doors shall be 45 inches high, 22 inches wide, and six inches deep.
S5.4.3 Restriction on wheelchair anchorage location.
S5.4.3.1 Except as provided in paragraph S5.4.3.2 of this section, no portion of a wheelchair securement anchorage shall be located in a school bus such that:
S5.4.3.2 The restriction in S5.4.3.1(a) of this section does not apply to tracks or track-type devices that are used for mounting seats and/or for wheelchair securement devices.
S5.5Emergency exit identification.
S5.5.1In buses other than school buses, and except for windows serving as emergency exits in accordance with S5.2.2.3(b) and doors in buses with a GVWR of 10,000 pounds or less, 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.

Code of Federal Regulations

Examples: (1) Lift to Unlatch, Push to Open

(2) Lift Handle and Push out to Open

When a release mechanism is not located within an occupant space of an adjacent seat, a label meeting the requirements of S5.5.2 that indicates the location of the nearest release mechanism shall be placed within the occupant space.

Code of Federal Regulations

Example: “Emergency Exit Instructions Located Next to Seat Ahead”

S5.5.2In buses other than school buses. Except as provided in S5.5.2.1, 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. The marking shall be legible from each of these locations when the other two corresponding locations are occupied.
S5.5.2.1If 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.
S5.5.3 School Bus.

Code of Federal Regulations

Examples: (1) Lift to Unlatch, Push to Open

(2) Turn Handle, Push Out to Open

S6. Test conditions.
S6.1The vehicle is on a flat, horizontal surface.
S6.2The inside of the vehicle and the outside environment are kept at any temperature from 70° to 85 °Fahrenheit for 4 hours immediately preceding the tests, and during the tests.
S6.3For the window retention test, windows are installed, closed, and latched (where latches are provided) in the condition intended for normal bus operation.
S6.4For the emergency exit release and extension tests, windows are installed as in S6.3, seats, armrests, and interior objects near the windows are installed as for normal use, and seats are in the upright position.

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[37 FR 9395, May 10, 1972]

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Editorial Note: For Federal Register citations affecting § 571.217 see the List of CFR Sections Affected which appears in the Finding Aids section of the printed volume and on GPO Access.