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.

S5.1   Window 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:

(a) A force of 1,200 pounds is reached.

(b) At least 80 percent of the glazing thickness has developed cracks running from the load contact region to the periphery at two or more points, or shattering of the glazing occurs.

(c) The inner surface of the glazing at the center of force application has moved relative to the window frame, along a line perpendicular to the undisturbed inner surface, a distance equal to one-half of the square root of the minimum surface dimension measured through the center of the area of the entire sheet of window glazing.

S5.1.1   An 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.

S5.1.2   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.

S5.2   Provision of emergency exits.

S5.2.1   Buses 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.

S5.2.1.1   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.

S5.2.2   Buses other than school buses.

S5.2.2.1   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. 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.

S5.2.2.2   Buses 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.

S5.2.2.3   Buses 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:

(a) Devices that meet the requirements of S5.3 through S5.5 without using remote controls or central power systems;

(b) Windows that can be opened manually 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; or

(c) Doors.

S5.2.3   School 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.

(a) One rear emergency door that opens outward and is hinged on the right side (either side in the case of a bus with a GVWR of 10,000 pounds or less), and the additional exits, if any, specified by Table 1.

(b) One emergency door on the vehicle's left side that is hinged on its forward side and meets the requirements of S5.2.3.2(a), and a push-out rear window that provides a minimum opening clearance 41 centimeters high and 122 centimeters wide and meets the requirements of S5.2.3.2(c), and the additional exits, if any, specified by Table 2.

(c) The area of an opening equipped with a wheelchair lift may be credited toward the required additional exits if it meets the requirements of paragraphs (a) or (b) of S5.2.3.1 and if the lift folds or stows in such a manner that the area is available for use by persons not needing the lift. With the lift in the folded or stowed position, such opening is considered a side emergency exit door.

S5.2.3.2   All emergency exits required by S5.2.3.1(a) and S5.2.3.1(b) shall meet the following criteria:

(a) Side emergency exit doors.

(1) Each side emergency exit door shall be hinged on its forward side.

(2) The first side emergency exit door installed pursuant to Table 1, shall be located on the left side of the bus and as near as practicable to the mid-point of the passenger compartment. A second side emergency exit door installed pursuant to Table 1 shall be located on the right side of the bus. In the case of a bus equipped with three side emergency door exits pursuant to Table 1, the third shall be located on the left side of the bus.

(3) The first side emergency exit door installed pursuant to Table 2 shall be located on the right side of the bus. A second side emergency door exit installed pursuant to Table 2 shall be located on the left side of the bus. In the case of a bus equipped with three side emergency door exits pursuant to Table 2, the third shall be located on the right side of the bus.

(4) No two side emergency exit doors shall be located, in whole or in part, within the same post and roof bow panel space.

(b) Emergency roof exit.

(1) Each emergency roof exit shall be hinged on its forward side, and shall be operable from both inside and outside the vehicle.

(2) In a bus equipped with a single emergency roof exit, the exit shall be located as near as practicable to the midpoint of the passenger compartment.

(3) In a bus equipped with two emergency roof exits, one shall be located as near as practicable to a point equidistant between the midpoint of the passenger compartment and the foremost limit of the passenger compartment and the other shall be located as near as practicable to a point equidistant between the midpoint of the passenger compartment and the rearmost point of the passenger compartment.

(4) In a bus equipped with three or more emergency roof exits, the roof exits shall be installed so that, to the extent practicable, the longitudinal distance between each pair of adjacent roof exits is the same and equal to the distance from the foremost point of the passenger compartment to the foremost roof exit and to the distance from the rearmost point of that compartment to the rearmost roof exit.

(5) Except as provided in paragraph (b)(6) of this section, each emergency roof exit shall be installed with its longitudinal centerline coinciding with a longitudinal vertical plane passing through the longitudinal centerline of the school bus.

(6) In a bus equipped with two or more emergency roof exits, for each roof exit offset from the longitudinal vertical plane specified in paragraph (b)(5) of this section, there shall be another roof exit offset from that plane an equal distance to the other side.

(c) Emergency exit windows. A bus equipped with emergency exit windows shall have an even number of such windows, not counting the push-out rear window required by S5.2.3.1(b). Any side emergency exit windows shall be evenly divided between the right and left sides of the bus. School buses shall not be equipped with horizontally-sliding emergency exit windows. Further, except for buses equipped with rear push-out emergency exit windows in accordance with S5.2.3.1(b), school buses shall not be equipped with both sliding and push-out emergency exit windows.

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.

S5.2.3.4   Each 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.

(a) Each bus shall be equipped with one rear emergency door that opens outward and is hinged on the right side (either side in the case of a bus with a GVWR of 4,536 kilograms or less); or

(b) Each bus shall be equipped with one emergency door on the vehicle's left side that is hinged on its forward side and meets the requirements of S5.2.3.2(a), and a push-out rear window that provides a minimum opening clearance 41 centimeters high and 122 centimeters wide and meets the requirements of S5.2.3.2(c).

S5.3   Emergency exit release.

S5.3.1   Each 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.

S5.3.2 (a) When 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 person, from inside the passenger compartment, using force applications each of which conforms, at the option of the manufacturer, either to S5.3.2.1(a) or S5.3.2.1(b).

(b) Each exit described in S5.3.2(a) shall have no more than two release mechanisms. For exits with one release mechanism, the exit shall require two force applications to open the exit: One force application shall be applied to the mechanism and another force application shall be applied to open the exit. The force application for the release mechanism must differ by not less than 90 degrees and not more than 180 degrees from the direction of the initial motion to open the exit. For exits with two release mechanisms, there shall be a total of three force applications to open the exit: One force application shall be applied to each of the two mechanisms to release each mechanism, and another force shall be applied to open the exit. The force application for at least one of the release mechanisms must differ by not less than 90 degrees and not more than 180 degrees from the direction of the initial motion to open the exit. The force applications for the mechanism(s) must conform to either S5.3.2.1(a) or S5.3.2.1(b), as appropriate.

S5.3.2.1(a) Low-force application.

(1) Location: As shown in Figure 1 or Figure 3.

(2) Type of motion: Rotary or straight.

(3) Magnitude: Not more than 90 N.

(b) High-force application.

(1) Location: As shown in Figure 2 or Figure 3.

(2) Type of motion: Straight and perpendicular to the undisturbed exit surface.

(3) Magnitude: Not more than 270 N.

S5.3.3 School bus emergency exit release.

S5.3.3.1   When 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.

(a) Location: Within the high force access region shown in Figure 3A for a side emergency exit door, within the high force access region shown in both Figure 3D(1) and Figure 3D(2) for an interior release mechanism for a rear emergency exit door, and within the high force access region shown in Figure 3D(1) for an exterior release mechanism for a rear emergency exit door.

(b) Type of motion: Upward from inside the bus and, at the discretion of the manufacturer, from outside the bus. Buses with a GVWR of 10,000 pounds or less shall provide interior release mechanisms that operate by either an upward or pull-type motion. The pull-type motion shall be used only when the release mechanism is recessed in such a manner that the handle, level, or other activating device, before being activated, does not protrude beyond the rim of the recessed receptacle.

(c) Magnitude of force: Not more than 178 newtons.

S5.3.3.2   When 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.

(a) Emergency exit windows—Low-force application.

(1) Location: Within the low-force access regions shown in Figures 1 and 3 for an emergency exit window.

(2) Type of motion: Rotary or straight.

(3) Magnitude: Not more than 89 newtons.

(b) Emergency exit windows—High-force application.

(1) Location: Within the high-force access regions shown in Figures 2 and 3 for an emergency exit window.

(2) Type of motion: Straight and perpendicular to the undisturbed exit surface.

(3) Magnitude: Not more than 178 newtons.

S5.3.3.3   When 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°.

(a) Emergency roof exits—Low-force application.

(1) Location: Within the low force access regions shown in Figure 3B, in the case of buses whose roof exits are not offset from the plane specified in S5.2.3.2(b)(5). In the case of buses which have roof exits offset from the plane specified in S5.2.3.2(b)(5), the amount of offset shall be used to recalculate the dimensions in Figure 3B for the offset exits.

(2) Type of motion: Rotary or straight.

(3) Magnitude: Not more than 89 newtons.

(b) Emergency roof exits—High-force application.

(1) Location: Within the high force access regions shown in Figure 3B, in the case of buses whose roof exits are not offset from the plane specified in S5.2.3.2(b)(5). In the case of buses which have roof exits offset from the plane specified in S5.2.3.2(b)(5), the amount of offset shall be used to recalculate the dimensions in Figure 3B for the offset exits.

(2) Type of motion: Straight and perpendicular to the undisturbed exit surface.

(3) Magnitude: Not more than 178 newtons.

S5.4   Emergency exit opening.

S5.4.1   After 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.

S5.4.2   School bus emergency exit opening.

S5.4.2.1   School buses with a GVWR of more than 10,000 pounds.

(a) Emergency exit doors. After the release mechanism has been operated, each emergency exit door of a school bus shall, under the conditions of S6., before and after the window retention test required by S5.1, using the force levels specified in S5.3.3, be manually extendable by a single person to a position that permits:

(1) In the case of a rear emergency exit door, an opening large enough to permit unobstructed passage into the bus of a rectangular parallelepiped 1,145 millimeters (45 inches) high, 610 millimeters (24 inches) wide, and 305 millimeters (12 inches) deep, keeping the 1,145 millimeter (45 inch) dimension vertical, the 610 (24 inch) millimeter dimension parallel to the opening, and the lower surface in contact with the floor of the bus at all times, until the bottom edge of the rearmost surface of the parallelepiped is tangent to the plane of the door opening; and

(2) In the case of a side emergency exit door, an opening at least 114 centimeters high and 61 centimeters wide.

(i) Except as provided in paragraph (a)(2)(ii) of this section, no portion of a seat or a restraining barrier shall be installed within the area bounded by the opening of a side emergency exit door, a vertical transverse plane tangent to the rearward edge of the door opening frame, a vertical transverse plane parallel to that plane at a distance of 30 centimeters forward of that plane, and a longitudinal vertical plane passing through the longitudinal centerline of the bus. (See Figure 5A).

(ii) A seat bottom may be located within the area described in paragraph (a)(2)(i) of this section 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 area described in paragraph (i) when the seat bottom is vertical. (See Figure 5B).

(iii) No portion of a seat or restraining barrier located forward of the area described in paragraph (a)(2)(i) of this section and between the door opening and a longitudinal vertical plane passing through the longitudinal centerline of the bus shall extend rearward of a vertical transverse plane tangent to the forwardmost portion of a latch mechanism on the door. (See Figures 5B and 5C.)

(3)

(i) Each emergency exit door of a school bus shall be equipped with a positive door opening device that, after the release mechanism has been operated, under the conditions of S6, before and after the window retention test required by S5.1—

(A) Bears the weight of the door;

(B) Keeps the door from closing past the point at which the door is perpendicular to the side of the bus body, regardless of the body's orientation; and

(C) Provides a means for release or override.

(ii) The positive door opening device shall perform the functions specified in paragraph (a)(3)(i) (A) and (B) of this section without the need for additional action beyond opening the door past the point at which the door is perpendicular to the side of the bus body.

(b) Emergency roof exits. After the release mechanism has been operated, each emergency roof exit of a school bus shall, under the conditions of S6, before and after the window retention test required by S5.1, using the force levels specified in S5.3.3, be manually extendable by a single person to a position that permits an opening at least 41 centimeters high and 41 centimeters wide.

(c) Emergency exit windows. After the release mechanism has been operated, each emergency exit window of a school bus shall, under the conditions of S6., both before and after the window retention test of S5.1, using force levels specified in S5.3.3.2, be manually extendable 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.

S5.4.2.2   School 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:

(a) In the case of side emergency exit doors, any portion of the wheelchair securement anchorage is within the space bounded by the interior side wall and emergency exit door opening, transverse vertical planes 305 mm (12 inches) forward and rearward of the center of any side emergency exit door restricted area, and a longitudinal vertical plane through the longitudinal centerline of the school bus, as shown in Figure 6A.

(b) In the case of rear emergency exit doors in school buses, using the parallelepiped described in S5.4.2.1(a)(1) (for school buses with a GVWR greater than 10,000 lb) or S5.4.2.2 (for school buses with a GVWR of 10,000 lb or less), when the parallelepiped is positioned, as described in S5.4.2.1(a), flush with the floor and with the rear surface of the parallelepiped tangent to the opening of the rear emergency exit door, there must not be any portion of a wheelchair securement anchorage within the space occupied by the parallelepiped or within the downward vertical projection of the parallelepiped, as shown in Figure 6C.

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.

S5.5   Emergency exit identification.

S5.5.1   In 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.

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.

S5.5.2   In 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.

S5.5.2.1   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.

S5.5.3 School Bus.

(a) Each school bus emergency exit provided in accordance with S5.2.3.1 shall have the designation “Emergency Door” or “Emergency Exit,” as appropriate, in letters at least 5 centimeters high, of a color that contrasts with its background. For emergency exit doors, the designation shall be located at the top of, or directly above, the emergency exit door on both the inside and outside surfaces of the bus. The designation for roof exits shall be located on an inside surface of the exit, or within 30 centimeters of the roof exit opening. For emergency window exits, the designation shall be located at the top of, or directly above, or at the bottom of the emergency window exit on both the inside and outside surfaces of the bus.

(b) Concise operating instructions describing the motions necessary to unlatch and open the emergency exit shall be located within 15 centimeters of the release mechanism on the inside surface of the bus. These instructions shall be in letters at least 1 centimeter high and of a color that contrasts with its background.

(c) Each opening for a required emergency exit shall be outlined around its outside perimeter with a retroreflective tape with a minimum width of 2.5 centimeters and either red, white, or yellow in color, that when tested under the conditions specified in S6.1 of Standard No. 131 (49 CFR 571.131), meets the criteria specified in Table 1 of that section.

(d) On the inside surface of each school bus with one or more wheelchair anchorage positions, there shall be a label directly beneath or above each “Emergency Door” or “Emergency Exit” designation specified by paragraph (a) of S5.5.3 of this standard for an emergency exit door or window. The label shall state in letters at least 25 mm (one inch) high, the words “DO NOT BLOCK” in a color that contrasts with the background of the label.

S6. Test conditions.

S6.1   The vehicle is on a flat, horizontal surface.

S6.2   The 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.

S6.3   For the window retention test, windows are installed, closed, and latched (where latches are provided) in the condition intended for normal bus operation.

S6.4   For 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.

Figure 3 Low and High-Force Access Regions for Emergency Exits Without Adjacent Seats

Figure 6B [Reserved]

Figure 6D [Reserved]

[37 FR 9395, May 10, 1972]