Read "Bus Operator Barrier Design: Guidelines and Considerations" at NAP.edu

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Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

APPENDIX A

Design Criteria Matrix

Page 58 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Colors are applied to highlight the relationship for comparison and contrast between cells in close proximity.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Operator Workstation	Workplace Width [Seat]	N/A	N/A	N/A	≥800 mm centered around operator centerline	The bus operator compartment should allow for clearance of the operator’s shoulders and elbows (min. 800 mm cross-bus).

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Operator Workstation	Workplace Width [Seat]	A, B, C	Clearance	Yes	Yes, >825 mm	Yes, >825 mm	Yes, >825 mm

Page 59 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Operator Workstation	Platform Height [Seat]	N/A	Allows a seated bus operator to see a target positioned 610 mm in front of the bumper and 1,067 mm above the ground. The height of the platform shall also allow the bus operator’s vertical upward view to be greater than or equal to 15°.	300 (±50) mm above the bus floor and be reachable by a single step. If the platform height is greater than 350 mm, steps with equal height shall be provided with a maximum height of 250 mm and a minimum height of 125 mm.	In low-floor buses, the driver’s workplace should be arranged on a platform. It is recommended that this platform be at a height of 300 ±50 mm above the floor and be reached by a single step. If the platform height is greater than 350 mm, steps with equal height shall be provided with a maximum height of 250 mm and a minimum height of 125 mm.	Allow a seated bus operator to see a target positioned 610 mm in front of the bumper and 1,067 mm above the ground. The height of the platform shall also allow the bus operator’s vertical upward view to be greater than or equal to 15°.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Operator Workstation	Platform Height [Seat]	A, B, C	Secondary	No interference	No interference	Driver’s environment has been developed to ensure the operator will be able to see a target positioned 610 mm in front of the bumper and 1,067 mm above the ground.	No interference

Page 60 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Back Angle Adjustment Range	±10°	Shall adjust in angle from a minimum of no more than 90° (upright) to at least 105° (reclined), with infinite adjustment in between.	10° to 25° (required) 0° to 30° (recommended)	+10° to +25° adjustable (required) 0° to 30° adjustable (recommended)	Shall adjust in angle from a minimum of no more than 0° (vertical) to at least 15° (reclined), with infinite adjustment in between. The preferred adjustment in angle ranges from 0° (vertical) to at least 30° (reclined).

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Back Angle Adjustment Range	A, B, C	Secondary	No interference	No interference	Seat has dual side recline to 105°	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Fore/Aft Adjustment Range (2)	185 mm	Shall travel horizontally a minimum of 229 mm. It shall adjust no closer to the heel point than 152 mm.	≥230 mm (required) ≥250 mm (recommended)	≥200 mm (required) ≥230 mm (recommended)	230 mm

Page 61 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Fore/Aft Adjustment Range (2)	A, B, C	Secondary	No interference	No interference	Seat has 238 mm fore/aft adjustment range.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Upward/Downward Adjustment Range	143 mm	N/A	120 mm	≥100 mm (required) ≥130 mm (recommended)	165 mm

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Upward/Downward Adjustment Range	A, B, C	Secondary	No interference	No interference	Active suspension seat has 31 mm upward/downward adjustment range in active mode and 81 mm in passive mode.	No interference

Page 62 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Pan Cushion Length (3)	N/A	Shall be no less than 419 mm at its minimum length and no more than 521 mm at its maximum length.	390–500 mm (required)	400–450 mm (required) 390–500 mm adjustable (recommended)	Shall be no more than 419 mm at its shortest length and extended to no more than 500 mm with a cushion extension feature. It is preferred that the seat pan cushion extension feature have multiple detent positions from its fully stowed to fully extended positions.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Pan Cushion Length (3)	A, B, C	Tertiary	No interference	No interference	Shall be no more than 419 mm at its shortest length and extended to no more than 500 mm with a cushion extension feature. It is preferred that the seat pan cushion extension feature have multiple detent positions from its fully stowed to fully extended positions.	No interference

Page 63 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Pan Cushion Width	N/A	432–533 mm across the front edge of the seat cushion; 508–584 mm across the side bolsters	≥480 mm (required)	≥450 mm (required) ≥480 mm (recommended)	432–533 mm across the front edge of the seat cushion; 508–584 mm across the side bolsters

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Pan Cushion Width	A, B, C	Clearance	No interference	No interference	Seat has a 559 mm wide seat cushion	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Pan Cushion Height (4)	N/A	Shall adjust in height from a minimum of 356 mm, with a minimum 152 mm vertical range of adjustment.	N/A	N/A	Shall adjust in height from a minimum of 356 mm, with a minimum 165 mm vertical range of adjustment.

Page 64 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Pan Cushion Height (4)	A, B, C	Tertiary	No interference	No interference	Active suspension seat has a min. of 361 mm and a max. of 442 mm height position in passive mode and a min. of 386 mm and a max. of 417 mm in active mode	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Seat	Seat Back Width	N/A	No less than 483 mm	≥475 mm (required)	≥475 mm (required)	No less than 483 mm

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Seat	Seat Back Width	A, B, C	Clearance	No interference	No interference	Seat has a 559 mm wide back cushion	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Steering Wheel	Wheel Diameter	457 mm	457–508 mm	450 (±25) mm (required) 450 mm (recommended)	≤500 mm (required) 450 (±25) mm (recommended)	457 (recommended) to 508 mm

Page 65 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Steering Wheel	Wheel Diameter	A, B, C	Clearance	No interference	No interference	The steering wheel has a 450 mm diameter. The steering wheel will be semi-circular or stadium-shaped to provide the operator with an unobstructed view of displays when the steering wheel is in the central position. The steering wheel should have controls on the horizontal spokes for commonly used functions. These controls should be operable with thumbs to allow the operator to grip the wheel while selections are shown on the central display screen.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Steering Wheel	Rim Diameter	N/A	22–32 mm	N/A	N/A	22–32 mm

Page 66 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Steering Wheel	Rim Diameter	A, B, C	Clearance	No interference	No interference	The steering wheel has a 34 mm rim diameter, but can be selected between 22 and 32 mm.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Steering Wheel	Rim Clearance	N/A	N/A	N/A	N/A	≥38 mm

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Steering Wheel	Rim Clearance	A, B, C	Clearance	No interference	No interference	The steering wheel has clearance with surrounding components of more than 38 mm.	No interference

Page 67 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Pedals	Spacing	N/A	25–51 mm measured at the heel of the pedals	Accelerator pedal: longitudinal spacing with bodywork (min. 50 mm); lateral spacing with bodywork (min. 30 mm). Brake pedal: clearance between accelerator pedal (min. 50 mm); lateral spacing with bodywork (min. 30 mm).	Accelerator pedal: longitudinal spacing with bodywork (≥50 mm); lateral spacing with bodywork (≥30 mm); clearance between accelerator and brake (50–75 mm; recommended). Brake pedal: clearance between brake pedal and any component (≥30 mm)	Accelerator pedal: longitudinal spacing with bodywork (min. 50 mm); lateral spacing with bodywork (min. 30 mm)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Pedals	Spacing	A, B, C	Tertiary	No interference	No interference	The accelerator and brake pedals have at least 50 mm longitudinal clearance with bodywork and between each other. Accelerator and brake pedals have at least 30 mm lateral clearance with bodywork.	No interference

Page 68 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Pedals	Footwell Depth	N/A	N/A	N/A	≥350 from AHP	Sufficient clearance within bus operator foot well shall be provided around the accelerator and brake pedals (min. 350 mm).

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Pedals	Footwell Depth	A, B, C	Clearance	No interference	No interference	The pedals will be adjustable hanging pedals.	No interference

Page 69 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Farebox	Positioning	Minimize obstruction of driver’s view	Minimize impact on passenger access and interference with the bus operator’s line of sight. Shall not restrict access to the bus operator area, shall not restrict operation of bus operator controls and shall not—either by itself or in combination with stanchions, transfer mounting, cutting and punching equipment, or route destination signs—restrict the bus operator’s field of view per SAE Recommended Practice J1050.	N/A	N/A	Position to minimize impact to passenger access and interference with the bus operator’s line of sight. It shall not restrict access to the bus operator area, operation of bus operator controls, or the bus operator’s field of view per SAE Recommended Practice J1050, either by itself or in combination with stanchions, transfer mounting, cutting and punching equipment, or route destination signs.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Farebox	Positioning	A, B, C	Secondary	No interference	No interference	The farebox will be positioned to minimize interference with the driver’s line of sight. Fareboxes will be placed at the front passenger entry and the middle door (or rear door in the absence of a middle door) for passenger entry when the operator barrier is deployed in rear-entry mode. Fare collection technology will display passengers’ fare payment status on operator’s electronic display screen.	The farebox being placed at the entry will make it easier to seal the operator environment with the barrier door. Placing the farebox away from the driver makes the driver less susceptible to attack from user. Configuration C can be reached with a farebox in the usual place.

Page 70 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Farebox	Height	Less than 914 mm above the floor	N/A	N/A	N/A	Position to minimize impact to passenger access and interference with the bus operator’s line of sight. It shall not restrict access to the bus operator area, operation of bus operator controls, or the bus operator’s field of view per SAE Recommended Practice J1050, either by itself or in combination with stanchions, transfer mounting, cutting and punching equipment, or route destination signs.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Farebox	Height	A, B, C	Tertiary	No interference	No interference	The farebox being placed at the entry, the height of it has no impact on the driver’s field of view.	The farebox being placed at the entry, the height of it has no impact on the driver’s field of view.

Page 71 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Door Control	Location	N/A	Shall be located in the operator’s area within the hand reach envelope described in SAE Recommended Practice J287, “Driver Hand Control Reach.” Shall provide tactile feedback to indicate commanded door position and resist inadvertent door actuation.	N/A	N/A	Represented by 3-D CAD Models

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Door Control	Location	A, B, C	Secondary	No interference	No interference	The door control will utilize rocker switches that give haptic feedback, placed very close at hand, potentially on the right-hand switch pod.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Floor	Height Above Ground	N/A	No more than 406 mm	N/A	N/A	N/A

Page 72 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Floor	Height Above Ground	N/A	Tertiary	N/A	N/A	Bus floor height is 394 mm from the ground.	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	Glare, General	N/A	Minimize to the extent possible. Front end: All colored, painted, and plated parts forward of the driver’s barrier shall be finished with a surface that reduces glare.	N/A	N/A	Minimize to the extent possible.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	Glare, General	A, C	Primary	Potential issue, material selection is crucial	Alleviated by closing to rear (open to driver) for driving	Barrier glazing can be lowered to reduce glaring. Glare from the barrier can be alleviated by closing to rear (open to driver). Fixed glazing is parallel to the line of sight to minimize obstruction. It should reach to vehicle “B” post to ensure a direct view to the windshield and side window.	Barrier glazing can be lowered to reduce glaring. Glare from the barrier can be alleviated by closing to rear (open to driver). Fixed glazing is parallel to the line of sight to minimize obstruction. It should reach to vehicle “B” Post to ensure a direct view to the windshield and side window.

Page 73 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	Glare, Exterior	N/A	The windshield shall be designed and installed to minimize external glare as well as reflections from inside the bus.	(same as interior)	N/A	Minimize to the extent possible.	(Mil-STD-1472 G) Exterior Sources: Visors or other means shall be used to preclude performance degradation due to glare from external sources such as sunlight or headlights. (9)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	Glare, Exterior	A, C	Reference	Potential issue, material selection is crucial	Alleviated by closing to rear (open to driver) for driving	Glares will be minimized to the extent possible, including using anti-glare coatings. The positioning of the barrier will minimize glare.	Glares will be minimized to the extent possible, including using anti-glare coatings. The positioning of the barrier will minimize glare.

Page 74 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	Glare, Interior	N/A	Objects within and adjacent to this area shall be matte black or dark gray in color wherever possible to reduce the reflection of light onto the windshield. The use of polished metal and light-colored surfaces within and adjacent to the driver’s area shall be avoided. Driver Area Barrier, Transit Coach: The barrier shall minimize glare and reflections in the windshield directly in front of the barrier from interior lighting during night operation. Interior Panels, Interior Lighting: The light source shall be located to minimize windshield glare.	Reflections due to light sources or other illuminated objects and reflections by sunlight should affect or impede as little as possible the view of the outside or the information devices and controls.	Reflections due to light sources or other illuminated objects, and reflections by sunlight, shall affect or impede as little as possible the view of the outside or the information devices and controls.	Minimize to the extent possible.	(Mil-STD-1472 G) Interior Sources: Interior surfaces shall be designed to reduce reflected glare into the bus operator’s eyes or onto the windshield. (9)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	Glare, Interior	A, C	Primary	Nontransparent pieces can be painted matte black without issue	Alleviated by closing to rear (open to driver) for driving, non-transparent pieces can be painted matte black without issue	Minimize to the extent possible. Nontransparent pieces can be painted matte black	Barrier glazing can be lowered to reduce glaring. Glare from the barrier can be alleviated by closing to rear (open to driver). Fixed glazing is parallel to the line of sight to minimize obstruction. It should reach to vehicle “B” Post to ensure a direct view to the windshield and side window.

Page 75 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	Glare, Displays	N/A	(same as interior)	(same as interior)	Reflections in windscreen originating from interior light sources shall be minimized to the extent possible.	Minimize to the extent possible.	(Mil-STD-1472 G) Interior displays: Interior displays shall be designed to reduce reflected glare into the bus operator’s eyes or onto the windshield. (9)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	Glare, Displays	A, C	Secondary	Non-transparent pieces can be painted matte black without issue	Alleviated by closing to rear (open to driver) for driving, nontransparent pieces can be painted matte black without issue	The position of the screens is adjustable so that the operator can position them to minimize glare in relation to his position. Sun shield can be added to reduce glare.	No interference

Page 76 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	General Illumination	N/A	Shall illuminate the half of the steering wheel nearest the bus operator to a level of 5-to-10-foot-candles.	N/A	N/A	Illuminate the half of the steering wheel closest to the driver to a level of 5-to-10-foot-candles.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	General Illumination	N/A	Tertiary	N/A	N/A	N/A	N/A

Page 77 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver’s Area	Noise	N/A	Overall Requirements, Interior Noise: The combination of inner and outer panels and any material used between them shall provide sufficient sound insulation so that a sound source with a level of 80 dB(A) measured at the outside skin of the bus shall have a sound level of 65 dB(A) or less at any point inside the bus… The driver area shall not experience a noise level of more than 75 dB(A). Measurements of interior noise levels shall be taken in accordance with SAE J2805. Interior Panels, Driver Area Barrier: The panel should be properly attached to minimize noise and rattles.	Driving noise at 50 km/h must not exceed 70 dB(A) at the bus operator’s ear height (measuring method in accordance with DIN ISO 5128). Noise level at low idle must not exceed 55 dB(A).	The driving noise, expressed as a L_eq (taken over 2 minutes) at 50 km/h, shall not exceed 70 dB(A) at the bus operator’s ear height (measured in accordance with ISO 5128). Noise level, when the bus is stationery and engine is idle, shall be < 60 dB(A). The noise level of the ventilation fan in the lowest position shall not exceed 55 dB(A) at the driver’s ear height. The noise level in the middle position (de-misting, directed to the windscreen) shall not exceed 65 dB(A) with the engine off. Noises with distinct and unpleasant tonal characteristics (clattering, grating, squeaking, etc.) shall be avoided.	70 dB(A) measured at the driver’s head position while driving.

Page 78 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver’s Area	Noise	A, B, C	Secondary	Barrier door is locked down during operation	Barrier door is locked down during operation	70 dB(A) measured at the driver’s head position while driving.	The barrier door creating a sealed environment for the operator in both positions will reduce noise from the passenger area.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Climate	General	N/A	N/A	Basic system must consist of conventional air heating and ventilation, optionally plus radiant panel heating.	Acceptable to the majority of the bus operators working in the normal conditions prevailing in the region throughout the year.	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Climate	General	A, B, C	Secondary	Minimal interference, potential benefits as explored in bus COVID barrier study	Minimal interference, potential benefits as explored in bus COVID barrier study	The barrier door creating a sealed environment for the operator will create an isolated climate zone.	The barrier door creating a sealed environment for the operator will create an isolated climate zone.

Page 79 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Climate	Controls and Temperature Uniformity	N/A	The HVAC system excluding the driver’s heater/defroster shall be centrally controlled with an advanced electronic/diagnostic control system with provisions for extracting/reading data. The system shall be compliant with J1939 Communication Protocol for receiving and broadcasting of data. Hot engine coolant water shall be delivered to the HVAC system driver’s defroster/heater and other heater cores by means of an auxiliary coolant pump, sized for the required flow, which is brushless and seal-less having a minimum maintenance-free service life for both the brushless motor and the pump of at least 40,000 hours at full power.	Heating Requirements: The set temperatures must be attainable in a normal operating condition and at an outside temperature of −15°C. The air outlet temperature must be within the range of 18°C to 25°C ± 2 K. The temperature gradient shall not be more than 2 K/m (preferably laminar distribution with the head area approx. 1 to 3 K cooler than the footwell). The required heating capacity must be attainable at an air velocity of < 0.2 m/s near the body area at max. blower speed and all air nozzles open. Special measures are to be provided to prevent ingress of cold air when the front door is open (e.g., optionally by high cabin door, separation above the cabin door, warm air curtain etc.). During the heating operation a surface temperature of > 14°C should be ensured (at side walls and floor).	Subject to agreement between the client and manufacturer. Recommended heating performance provided in Annex A (informative).	N/A	Per FMVSS No. 103, S4. Except as provided in paragraph (b) of this section [applicable to non-continental US bus manufacturing], each passenger car shall meet the requirements specified in S4.1, S4.2, and S4.3, and each multipurpose passenger vehicle, truck, and bus shall meet the requirements specified in S4.1. S4.1: Each vehicle shall have a windshield defrosting and defogging system. (13) Criteria should be applied from SAE J381-JUN2020 Recommended Practice for defrosting performance of windshield target and defrosting performance of side window project mirror perimeter. (14)

Page 80 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Climate	Controls and Temperature Uniformity	B, C	Secondary	Minimal interference, potential benefits as explored in bus COVID barrier study. Defogging and defrosting of barrier glazing surface should be provided at the same level of performance as driver-side glass and passenger entry door glass if glazing is between the view of the bus operator and the curbside mirror or side entry door glass.	Minimal interference, potential benefits as explored in bus COVID barrier study. Defogging and defrosting of barrier glazing surface should be provided at the same level of performance as driver-side glass and passenger entry door glass.	Separate zones must offer the advantage that users’ needs may differ from those of the operator, especially in winter	Separate zones must offer the advantage that users' needs may differ from those of the operator. Especially in winter, defogging and defrosting of barrier glazing surface should be provided at the same level of performance as driver-side glass and passenger entry door glass.

Page 81 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Climate	Controls and Temperature Uniformity (alternative)	N/A	Manually Adjustable Temperature Control Set Point: The climate control system shall have the provision to allow the driver to adjust the temperature control setpoint at a minimum of between 68°F and 72°F. From then on, all interior climate control system requirements shall be attained automatically, unless re-adjusted by the driver. The driver shall have full control over the defroster and driver’s heater. The driver shall be able to adjust the temperature in the driver’s area through air distribution and fans. The interior climate control system shall switch automatically to the ventilating mode if the refrigerant compressor or condenser fan fails.	Overall Requirements: Heating and ventilation in the driver’s cab must be independently controllable from the passenger compartment.	Basic Requirements: The climate and ventilation in the driver’s cab shall be controllable independently of that of the passenger compartment.	N/A

Page 82 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Climate	Controls and Temperature Uniformity (alternative)	B, C	Tertiary	Should provide at least a slight advantage in maintaining operator area temperature separate to passenger area temperature	Should provide at least a slight advantage in maintaining operator area temperature separate to passenger area temperature	The separated climate zone will allow operator to have a better control of their environment to ensure comfort.	The separated climate zone will allow operator to have a better control of their environment to ensure comfort.

Page 83 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Airflow	Driver’s Area	N/A	The bus interior climate control system shall deliver at least 100 cfm of air to the driver’s area when operating in the ventilating and cooling modes. Adjustable nozzles shall permit variable distribution or shutdown of the airflow… [excerpt only]	Overall Requirements: Interference from the door area and the passenger compartment must be reduced as much as possible (preferably overpressure in the driver’s cab). Air velocity and temperatures should not be influenced by the vehicle speed. Ventilation Requirements: Additional air nozzles or air jets in the direction of the driver to be provided (e.g., two outlet nozzles in the dashboard with adjustment for the rate of airflow and its direction). At maximum fan output an air velocity > 5 m/s must be attainable (measured directly at the air nozzle outlet).	Ventilation: The ventilation fan shall have a minimum of three speed settings. Additional adjustable air nozzles for direct air jets in the direction of the driver shall be provided. The airflow should be such that the nozzles can be closed if required.	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Airflow	Driver’s Area	B, C	Secondary	Should provide at least a slight advantage in maintaining positive air pressure from operator area to passenger area	Should provide at least a slight advantage in maintaining positive air pressure from operator area to passenger area	The operator barrier will fully enclose the operator and help to create positive pressure isolation.	The operator barrier will fully enclose the operator and help to create positive pressure isolation.

Page 84 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Airflow	Air Quality, Driver [Driver’s Compartment Requirements]	N/A	A separate heating, ventilation and defroster system for the driver’s area shall be provided and shall be controlled by the driver. The system shall meet the following requirements: Fan(s) shall be able to draw air from the bus body interior and/or exterior through a control device and pass it through the heater core to the defroster system and over the driver’s feet. A minimum capacity of 100 cfm shall be provided. The driver shall have complete control of the heat and fresh airflow for the driver’s area. A ventilation system shall be provided to ensure driver comfort and shall be capable of providing fresh air in both the foot and head areas… [excerpt only]	Air Quality Requirements: The bus operator’s cab must be ventilated with 75% outside air. For the filtration of the outside air, outside air filters must have a retention rate of at least 50% for particles ≥ 3 m. There must also be a manually controlled air recirculation system. The fresh air supply must be drawn from a low pollution area (e.g., roof intake). For the filtration of the outside air, outside air filters must be used (particle filters) with the following criteria: retention rate of at least 50% for particles ≥ 3 m, diagnosis solution for degree of filter fouling (optionally), optional or additional absorption filter.	Air Quality: Driver’s workplace shall be capable of being ventilated from either external ambient air or re-circulated cabin air per ISO/TS 11155-1 and ISO/TS 11155-2. Recommended performance of a typical cabin air filter is provided in Annex B (informative).	Outside air should be provided to the operator workstation at a minimum rate of 0.57 m³ (20 ft³)/min. Air speed at the operator’s head should be adjustable either continuously or with not less than three discrete increments from near 0 to 120 m (400 ft)/min. The operator workstation must be ventilated with 75% outside air and filtered with a retention rate of at least 50% for particles ≥ 3 m.

Page 85 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Airflow	Air Quality, Driver [Driver’s Compartment Requirements]	C	Secondary	Should provide at least a slight advantage in maintaining positive air pressure and separate temperature control from operator area to passenger area, potential benefits as explored in bus COVID barrier study	Should provide at least a slight advantage in maintaining positive air pressure and separate temperature control from operator area to passenger area, potential benefits as explored in bus COVID barrier study	The operator barrier will fully enclose the operator to create positive pressure isolation. Operator compartment will be ventilated with some outside air. Filtration of outside air should be MERV-13 or better.	The operator barrier will fully enclose the operator and help to create positive pressure isolation

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Airflow	Air Quality, Passenger Area (default)	N/A	No “Fresh Air” Requirements: To be used by agencies that have an operating profile where the door opening cycle results in effectively providing an adequate “fresh air” mixture.	N/A	N/A	N/A

Page 86 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Airflow	Air Quality, Passenger Area (default)	N/A	Secondary	N/A	N/A	Should have vertical downstream ventilation for the passenger area to prevent virus and bacteria to propagate from one to others	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Ventilation, Airflow	Air Quality, Passenger Area (alternatives)	N/A	(1) Requirement for 10 Percent “Fresh Air” Mixture: The air shall be composed of no less than 10 percent outside air. (2) Air purification system. (3) Ionization system. (4) Ultraviolet system.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Ventilation, Airflow	Air Quality, Passenger Area (alternatives)	C	Secondary	N/A	N/A	Should have vertical downstream ventilation for the passenger area to prevent virus and bacteria to propagate from one to others	N/A

Page 87 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	General	N/A	A barrier or bulkhead between the driver and the street-side front passenger seat shall be provided.	N/A	Appendix D, Basic Security for the Driver: Door of the driver’s place with no direct entry to the driver’s cabin, in the back shielded toward the passenger area, provide a separation in the back side of the driver around to shoulder, theft protection space for driver’s bag or valuables, door and door control for regulation of the passenger flow.	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	General	A, B, C	Primary	Yes	Yes	Barrier and barrier door provide a fully enclosed zone for the driver	Both barrier door positions provide a fully enclosed zone for the driver.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Glare	N/A	The barrier shall minimize glare and reflections in the windshield directly in front of the barrier from interior lighting during night operation.	N/A	N/A	N/A

Page 88 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Glare	A, B, C	Primary	Potential issue, material selection and finishing (e.g., painting nontransparent pieces matte black) is crucial	Alleviated by closing to rear (open to driver) for driving, non-transparent pieces can be painted matte black without issue	Barrier door glazing can be lowered to reduce glaring. Glare from the barrier can be alleviated by closing to rear (open to driver). Non-transparent pieces can be painted matte black without issue	Barrier door glazing can be lowered to reduce glaring. Glare from the barrier can be alleviated by closing to rear (open to driver).

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Location, Part 1	N/A	Location and shape must permit full seat travel and reclining possibilities that can accommodate the shoulders of a 95th-percentile male.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Location, Part 1	A, B, C	Clearance	No interference	No interference	Driver’s environment has been developed to permit full seat travel and reclining possibilities.	No interference

Page 89 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Location, Part 2	N/A	The partition shall have a side return and stanchion to prevent passengers from reaching the driver by standing behind the driver’s seat. The lower area between the seat and panel must be accessible to the driver.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Location, Part 2	A, B, C	Primary	No interference	No interference	Barrier and barrier door provide a fully enclosed zone for the driver to prevent passengers from reaching the driver.	Barrier door provides a fully enclosed zone for the driver to prevent passengers from reaching the driver.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Strength	N/A	The partition must be strong enough in conjunction with the entire partition assembly for mounting of such equipment as flare kits, fire extinguishers (1.2 kg), microcomputer, public address amplifier, etc.	N/A	N/A	N/A

Page 90 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Strength	A, B, C	Reference	N/A	N/A	The partition is strong enough in conjunction with the entire partition assembly for mounting of such equipment as flare kits, fire extinguishers (1.2 kg), microcomputer, public address amplifier, etc.	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Noise	N/A	The panel should be properly attached to minimize noise and rattles.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Noise	A, B, C	Primary	Yes	Yes	Electromagnetic lock for the barrier door eliminates rattle noise from standard mechanical lock.	Electromagnetic lock for the barrier door eliminates rattle noise from standard mechanical lock.

Page 91 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Size (default)	N/A	Wheel-Well-to-Ceiling Configuration of Driver’s Barrier: The driver’s barrier shall extend from the top of the wheel well to the ceiling the level of the seated driver and shall fit close to the bus side windows and wall to prevent passengers from reaching the driver or the driver’s personal effects.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Size (default)	A, B, C	Primary	Yes	Yes	N/A	Both barrier positions provide a fully enclosed zone for the driver.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Size (alternative)	N/A	Full-Height (Floor-to-Ceiling) Configuration of Driver’s Barrier: The driver’s barrier shall extend continually from the floor area to the ceiling and from the bus wall to the first stanchion immediately behind the driver to provide security to the driver and to limit passenger conversation.	N/A	N/A	N/A

Page 92 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Size (alternative)	A, B, C	Primary	No interference	No interference	N/A	Both barrier positions provide a fully enclosed zone for the driver.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver Area Barrier	Size (alternative)	N/A	Driver enclosure or door.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver Area Barrier	Size (alternative)	A, B, C	Primary	Yes	Yes	Barrier and barrier door provide a fully enclosed zone for the driver.	Both barrier positions provide a fully enclosed zone for the driver.

Page 93 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Modesty Panels	General	N/A	Sturdy divider panels constructed of durable, unpainted, corrosion-resistant material complementing the interior shall be provided to act as both a physical and visual barrier for seated passengers.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Modesty Panels	General	N/A	Reference	N/A	N/A	N/A	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Modesty Panels	Strength	N/A	The modesty panel and its mounting shall withstand a static force of 250 lbs applied to a 4- × 4-in. area in the center of the panel without permanent visible deformation.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Modesty Panels	Strength	N/A	Reference	N/A	N/A	N/A	N/A

Page 94 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Operation	N/A	When in an open position, the window shall not rattle or close during braking.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Operation	N/A	Reference	N/A	N/A	Can be accommodated by proper equipment selection.	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Visibility, Location and Size	N/A	The driver’s view, perpendicular through operator’s side window glazing, should extend a minimum of 33 in. (840 mm) to the rear of the heel point on the accelerator, and in any case must accommodate a 95th percentile male operator. The view through the glazing at the front of the assembly should begin not more than 26 in. (560 mm) above the operator’s floor to ensure visibility of an under-mounted convex mirror. Driver’s window construction shall maximize ability for full opening of the window.	Appendix D, Lateral and Front Visibility: Angle V, > 40 degrees required; ≥ 43 degrees recommended [reference seat H-Point in medium position [angle V is U angle < 10 degrees forward of a vertical plane that is parallel with the lateral axis of the vehicle]	N/A	The driver’s view, perpendicular through operator’s side window glazing, should extend a minimum of 1,008 mm to the rear of the heel point on the accelerator and must accommodate a 95th percentile male operator. The view through the glazing at the front of the assembly should begin not more than 26 in. (560 mm) above the operator’s floor to ensure visibility of an under-mounted convex mirror.

Page 95 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Visibility, Location and Size	A, B, C	Primary	No interference	No interference	The street-side window could be extended (beyond current design) rearward to accommodate a wide peripheral view with operator looking toward the left front.	No interference

Page 96 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Visibility, Transmittance	N/A	Light transmittance shall be 75 percent on the glass area below 53 in. from the operator platform floor. On the top-fixed-over-bottom-slider configuration, the top fixed area above 53 in. may have a maximum 5 percent light transmittance.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Visibility, Transmittance	A, B, C	Primary	No interference	No interference	Can be accommodated by proper equipment selection.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Materials, Tint	N/A	The glazing material shall have a single-density tint.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Materials, Tint	A, B, C	Primary	No interference	No interference	Can be accommodated by proper equipment selection.	No interference

Page 97 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Materials, Strength (default)	N/A	The driver-side window glazing material shall have a ¼ in. nominal thickness laminated safety glass conforming to the requirements of ANSI Z26.11996 Test Grouping AS-2 and the recommended practices defined in SAE J673.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Materials, Strength (default)	A, B, C	Primary	No interference	No interference	Can be accommodated by proper equipment selection.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Driver-side Window	Materials, Strength (alternative)	N/A	The driver-side window glazing material shall have a ¼ in. nominal thickness tempered safety glass conforming to the requirements of ANSI Z26.1-1996 Test Grouping AS-2 and the recommended practices defined in SAE J673.	N/A	N/A	N/A

Page 98 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Driver-side Window	Materials, Strength (alternative)	A, B, C	Primary	No interference	No interference	Can be accommodated by proper equipment selection.	No interference

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Passenger Doors	Dimensions, General (default)	N/A	When open, the doors shall leave an opening no less than 75 in. in height. Front door clear width shall be a minimum of 31 ¾ in. with the doors fully opened… [excerpt only]	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Passenger Doors	Dimensions, General (default)	B, C	Reference	N/A	No interference	A single leaf full glass door is used to minimize view obstruction to the side.	No interference

Page 99 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
ADA Wheelchair	General	N/A	Interior Circulation: Maneuvering room inside the bus shall accommodate easy travel for a passenger in a wheelchair from the loading device and from the designated securement area.	N/A	N/A	N/A	Vehicles [buses] shall be readily accessible to and usable by individuals with disabilities. (5) The driver seat platform shall not extend into the aisle beyond the wheel housing. (6)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
ADA Wheelchair	General	A, B	Primary	Extends into aisle but leaves sufficient passage.	Extends into aisle but leaves sufficient passage (33.3 in. minimum lateral clearance).	BOF wheelchair access primarily rear door entry.	BOF wheelchair access primarily rear door entry. Design can be modified to accommodate front entry wheelchair access.

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Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
ADA Wheelchair	Clearance Width	N/A	No width dimension should be less than 34 in. Areas requiring 90° turns of wheelchairs should have a clearance arc dimension no less than 45 in., and in the parking area where 180° turns are expected, space should be clear in a full 60 in. diameter circle. A vertical clearance of 12 in. above the floor surface should be provided on the outside of turning areas for wheelchair footrests.	N/A	N/A	N/A	Minimum clear width of 30 in. (6)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
ADA Wheelchair	Clearance Width	A, B	Primary	Extends into aisle but leaves sufficient passage.	Extends into aisle but leaves sufficient passage (33.3 in. minimum lateral clearance; bus aisle is 34.6 in., so it is exceedingly difficult not to impede on 34 in. APTA requirement).	BOF wheelchair access primarily rear door entry.	BOF wheelchair access primarily rear door entry. Design can be modified to accommodate front entry wheelchair access.

Page 101 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
ADA Wheelchair	Clearance Length	N/A	N/A	N/A	N/A	N/A	Provide a clear path for mobility aids at minimum length of 48 in. (6)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
ADA Wheelchair	Clearance Length	A, B	Primary	No interference	No interference	BOF wheelchair access primarily rear door entry.	BOF wheelchair access primarily rear door entry. Design can be modified to accommodate front entry wheelchair access.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
ADA Wheelchair	Securement	N/A	N/A	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
ADA Wheelchair	Securement	N/A	Tertiary	N/A	N/A	Wheelchair securement will be front facing and rear facing with an option for automated self-securement.	N/A

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Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
General Safety	Fire Safety, Materials, Default	N/A	All materials used in the construction of the passenger compartment of the bus shall be in accordance with the Recommended Fire Safety Practices defined in FMVSS 302.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
General Safety	Fire Safety, Materials, Default	N/A	N/A	N/A	N/A	Material selection can satisfy	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
General Safety	Fire Safety, Materials, Alternative	N/A	All materials used in the construction of the passenger compartment of the bus shall be in accordance with the Recommended Fire Safety Practices defined in FTA Docket 90-A, dated October 20, 1993…	N/A	N/A	N/A

Page 103 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
General Safety	Fire Safety, Materials, Alternative	N/A	N/A	N/A	N/A	Material selection can satisfy	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Side Windows	Materials, Default	N/A	Safety Glass Glazing Panels: Side windows glazing material shall have a minimum of 3/16 in. nominal thickness tempered safety glass. The material shall conform to the requirements of ANSI Z26.1-1996 Test Grouping 2 and the recommended practices defined in SAE J673.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Side Windows	Materials, Default	A, B, C	Primary	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy

Page 104 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Side Windows	Materials, Alternative	N/A	Polycarbonate Glazing Panels: Side window glazing material shall have a minimum 3/16 in. nominal thickness. The material shall conform with the requirements of ANSI Z26.11996, “Standard for Type AS-5 Safety Glazing Materials,” except for Test Number 17, which shall subject the specimens to 100 cycles with less than 4 percent hazing and 500 cycles with less than 12 percent hazing. Windows shall be polycarbonate sheet with an abrasion-resistant coating on both sides of the window.	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Side Windows	Materials, Alternative	A, B, C	Primary	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy

Page 105 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	General	N/A	N/A	N/A	N/A	N/A	The transparent material of the barrier located to the right of the driver is an interior partition composed of motor vehicle “glazing” that must comply with FMVSS No. 205, “Glazing materials.” Manufacturers or distributors that cut the glazing into components for use in motor vehicles or items of motor vehicle equipment must ensure the glazing meets the requirements of FMVSS No. 205. (10, 1)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	General	A, B, C	Primary	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy

Page 106 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	Panels	N/A	N/A	N/A	N/A	N/A

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	Panels	C	Primary	N/A	N/A	Two panels with glass at top and metal at bottom matching the style of the barrier door will create the total enclosure of the operator. One secondary panel is just behind the front door and at right angles to the axis of the bus. The other secondary panel is in plane with the B pillar and the operator’s eyes. Both secondary panels must achieve a seal to maintain positive pressure isolation (this does not refer to measurable pressure).	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	Materials, Strength	N/A	N/A	N/A	N/A	N/A	According to NHTSA, any transparent material to the right of a driver is an interior partition motor vehicle glazing that must comply with FMVSS No. 205, Glazing materials. FMVSS No. 205 requires by reference that the material comply with ANSI/SAE Z26.11996 fracture test. (1, 10)

Page 107 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	Materials, Strength	A, B, C	Primary	Material selection can satisfy	Material selection can satisfy	The glazing will withstand 500 lbs of force without breaking.	The glazing will withstand 500 lbs of force without breaking.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	Materials, Fire Safety	N/A	N/A	N/A	N/A	N/A	According to NHTSA the barrier should not impact vehicle compliance with flammability of interior materials required by FMVSS No. 302. (3, 10)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	Materials, Fire Safety	A, B, C	Reference	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy

Page 108 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	Materials, Transparency	N/A	N/A	N/A	N/A	N/A	According to NHTSA, any portion of barrier glazing that the driver sees through in order to view windows required for driving visibility is also required for driving visibility. (1, 10)

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	Materials, Transparency	A, B, C	Primary	Material selection can satisfy	Alleviated by closing to rear (open to driver) for driving, material selection can satisfy	Alleviated by closing to rear (open to driver) for driving. Fixed glazing is parallel to the line of sight to minimize obstruction. It should reach to vehicle B-pillar to ensure a direct view to the windshield and side window. Material selection can satisfy.	Alleviated by closing to rear (open to driver) for driving. Fixed glazing is parallel to the line of sight to minimize obstruction. It should reach to vehicle B-pillar to ensure a direct view to the windshield and side window. Material selection can satisfy.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier	Passenger Service, Fare	N/A	N/A	N/A	N/A	N/A	C-25 New: Passengers shall be able to access the farebox when the barrier is in the bus operator secured position.

Page 109 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier	Passenger Service, Fare	A, B	Primary	No interference, access is maintained	No interference, access is maintained	Fareboxes are located at front and rear entry locations so that farebox is accessible when the bus is in front entry and rear entry modes.	Farebox is located next to entry doors, so there is no interference with the barrier door. In case of farebox in standard location, the access is maintained.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	Report 185 Guidelines	Other
Bus Operator Barrier, Door	Access	N/A	N/A	Clear and unrestricted access to the driver’s workplace shall be ensured, with a required passage width of at least 450 mm (see ECE R107). A passage width of at least 500mm is recommended. The door lock should be well reachable. Appendix D: Driver’s cabin door with safety window (anti-aggression construction) with integrated cashpoint, safety window with cutout to speak, and adaptation of the driver’s cabin rear wall to minimize the clearance between cabin and cabin door.	Driver’s Workplace in General, Access to the Driver’s Workplace: Clear and unrestricted access to the bus operator’s workplace shall be ensured, with a passage width of at least 500 mm.	Platform Access: If the driver’s platform is 300 mm (± 50 mm) above the bus floor, a single step should be provided. If the platform height is greater than 350 mm, steps with equal vertical spacing shall be provided with a maximum and minimum vertical spacing of 250 mm and 125 mm, respectively.

Page 110 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Access	A, B, C	Primary	No interference	No interference, minimum access width is 797.3 mm	BOF bus operator workstation will be separated from the passenger entry area with a floor-to-ceiling barrier that will require a large opening to walk into the workstation while climbing up at least one step near the barrier.	Minimum access width is 709 mm

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Emergency Access	N/A	N/A	N/A	N/A	If a rectangular emergency access hatch is provided through the driver-side glass, the hatch must have a height of at least 650 mm and a width of at least 470 mm. [SAE J185]	The barrier should not prevent the driver from readily accessing emergency exits which comply with FMVSS No. 217. (10, 11)

Page 111 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Emergency Access	A, B, C	Primary	No interference, door can easily be opened by driver.	No interference, door can be operated pneumatically or manually switched to free-swinging.	Driver can access emergency exit through the driver-side glass. Barrier door can be operated mechanically or manually for emergency exit. Emergency access to the operator’s compartment is achieved by activating the battery cutoff switch.	No interference, the door can be operated mechanically or manually switched to free swinging. Emergency access to the operator’s compartment is achieved by activating the battery cutoff switch.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Size, Height, and Width	N/A	N/A	Appendix D, Figure 1 (see Figure 2): L1 maximum distance = 400 mm (rearward of accelerator heel point); L2 minimum distance = 1,600 mm (above passenger entry floor)	N/A	CAD Model: When the door provides access to the driver workstation platform through a large enclosure the recommended door width is 680 mm (26.8 in.), and the height should provide clearance of 1,800 mm (70.9 in.) above a nearby workstation platform step. [SAE J185]

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Size, Height, and Width	B, C	Primary	Yes	Yes, minimum access width is 797.3 mm	Access width is 709 mm and height is 1,867 mm	Access width is 709 mm and height is 1,867 mm

Page 112 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Operation	N/A	N/A	N/A	N/A	N/A	C-25 New: Configuration A barrier may be operated manually and automatically. Configuration B shall be operated automatically based on the state of the passenger entry door and shall be capable of being released by the bus operator only for customer service or in the case of emergency. When released the Configuration B barrier shall be capable of latching at both bus operator workstation and standee line positions.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Operation	A, B, C	Primary	Operated manually in most cases we have seen	Main operation controlled by pneumatic cylinder. This can be controlled either by driver or by an automated system, and the cylinder can be opened to atmosphere on both sides for free-swinging operation in case of emergency. Door is secured by electromagnet latch in driving position, can also be included for passenger access position.	The door would be manual or automated depending on preference. Main operation can be controlled by the driver or by an automated mechanical system, and the mechanical system can be deactivated for free-swinging operation in case of emergency. Door is secured by electromagnetic latch in both barrier door positions.	Main operation can be controlled by driver or by an automated mechanical system, and the mechanical system can be deactivated for free-swinging operation in case of emergency. Door is secured by electromagnetic latch in both barrier door positions.

Page 113 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Modes	N/A	N/A	N/A	N/A	N/A	C-25 New: The range of modes include (1) parked-passenger entry, (2) parked-customer service, (3) driving, and (4) emergency access. Configuration A barrier shall be operated manually during all modes. Configuration B barrier shall operate automatically between parked-passenger entry and driving modes; and it shall operate manually in parked-customer service and emergency access modes.

Page 114 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Modes	A, B, C	Primary	Operated manually in most cases we’ve seen	Main operation controlled by pneumatic cylinder. This can be controlled either by driver or by an automated system, and the cylinder can be opened to atmosphere on both sides for free-swinging operation in case of emergency or for passenger assist	BOF Configuration C modes include (1) front-passenger entry, (2) parked-customer service, (3) rear passenger entry driving, (4) emergency access, and (5) emergency rapid window closure. All modes can be controlled either by driver or by an automated system. The door will have glazing that opens vertically as in a standard car door using pneumatic power that can be employed to physically interrupt an assault (referred to as “emergency rapid closure”) and lowered at the discretion of the operator.	BOF Configuration C modes include (1) front passenger entry, (2) parked-customer service, (3) rear passenger, (4) emergency access, and (5) emergency rapid window closure. All modes can be controlled either by driver or by an automated system. The door will have glazing that opens vertically as in a standard car door using pneumatic power that can be employed to physically interrupt an assault (referred to as “emergency rapid closure”) and lowered at the discretion of the operator.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Glazing	N/A	N/A	N/A	N/A	N/A

Page 115 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Glazing	unknown	unknown	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy	Material selection can satisfy

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Bus Operator Barrier, Door	Latching	N/A	N/A	N/A	N/A	N/A

Page 116 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Bus Operator Barrier, Door	Latching	C	Primary	N/A	Door is secured by electromagnet latch in driving position, can also be included for passenger access position	The barrier will have a door for operator egress that latches in a standard position immediately to driver’s right (“front-entry mode,” referring to the ability of passengers to enter the bus through the front door) and latches to the wall in an alternative position horizontally across the bus to eliminate any optical effects (“rear-entry mode,” referring to passengers having to enter to the bus through the middle or rear doors). The door will close with an electromagnetic latch with 600 lbs of latching force to prevent rattling.	The barrier will have a door for operator egress that latches in a standard position immediately to driver’s right (“front-entry mode,” referring to the ability of passengers to enter the bus through the front door) and latches to the wall in an alternative position horizontally across the bus to eliminate any optical effects (“rear entry mode,” referring to passengers having to enter the bus through the middle or rear doors). The door will close with an electromagnetic latch with 600 lbs of latching force to prevent rattling.

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Mirror	Visibility, Street Side	N/A	N/A	N/A	N/A	N/A

Page 117 Bookmark

Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Mirror	Visibility, Street Side	N/A	N/A	N/A	N/A	Mirrors will be replaced by a camera mirror system. The cameras will be mounted low, barely above 95th percentile male eye height to avoid lenses that distort distance. Avoid wide angle lenses to the extent possible. Camera mirror system will show everything that is not observable through direct vision. Wide angle distortion of distance is to be minimized by increasing direct vision through window design.	N/A

Design Variables		TCRP Report 25 Guidelines	APTA SBP Guidelines	European Bus System of the Future	ISO 16121-1 through 4	TCRP Report 185 Guidelines	Other
Mirror	Visibility, Curbside	N/A	The roadside rearview mirror shall be positioned so that the driver’s line of sight is not obstructed.	All drivers must have a good view of the mirrors. Option: A construction (e.g., barrier) to refuse passengers the opportunity to stand at the front right of the bus, which occludes the driver’s view, shall be provided.	Lateral Visibility: If there is a service door located at the front corner of the vehicle, a cube measuring 100 x 100 x 100 mm, positioned adjacent to the door at a height of 800 mm above the ground, shall be visible either directly or indirectly.	N/A	Mirrors [or other objects] mounted on the interior of the bus should not block the curbside exterior mirror reflective surfaces when in driving mode. (9) The barrier should not obstruct the driver’s view of the mirrors and/or rearview image required for FMVSS No. 111 when in driving mode. (10, 12)

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Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

Design Variables		C-25 Priority (A/B/C)	C-25 Criteria	Concept A Status	Concept B Status	BOF Design	Concept C Status
Mirror	Visibility, Curbside	A, B, C	Primary	Ideally minimal impediment, to be analyzed further in Task 4	Driving position holds barrier door out of any possible driver view obstruction	The low mounting of the camera allows seeing from the front wheel contact point to the horizon without the use of extreme wide angle, expanding apparent distance to objects, and thereby distorts perception of speed. Camera housing aerodynamics must prevent creation of bound vortices that fling rain and debris forward, obscuring vision	Driver should have a direct view to the curbside mirror without having to look through other glazing at the windshield

Design Criteria References

1. Barrier Materials: FMVSS No. 205; Glazing materials.

2. Barrier Materials: ANSI/SAE Z26.1-1996.

3. Barrier Materials: FMVSS No. 302; Flammability of interior materials.

4. Barrier Materials: SAE J673_202107; (R) Automotive Safety Glazing Materials.

5. ADA Transportation Services: 49 CFR PART 37—Transportation Services for Individuals with Disabilities (ADA) [https://www.ecfr.gov/current/title-49/subtitle-A/part-37], 37.7 Standards for accessible vehicles. (a).

6. Wheelchair clearance dimensions: 49 CFR Part 38—Americans with Disabilities Act (ADA) Accessibility Specifications for Transportation Vehicles [https://www.ecfr.gov/current/title-49/subtitle-A/part-38/subpart-B], Subpart B—Buses, Vans and Systems, 38.29—Interior circulation, handrails and stanchions. (e).

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Suggested Citation: "Appendix A: Design Criteria Matrix." National Academies of Sciences, Engineering, and Medicine. 2024. Bus Operator Barrier Design: Guidelines and Considerations. Washington, DC: The National Academies Press. doi: 10.17226/27877.

7. Wheelchair clearance dimensions: 49 CFR Part 38—Americans with Disabilities Act (ADA) Accessibility Specifications for Transportation Vehicles [https://www.ecfr.gov/current/title-49/subtitle-A/part-38/subpart-B], Subpart B—Buses, Vans and Systems, 38.23—Mobility aid accessibility. (b) Vehicle lift—(6) Platform surface.

8. Wheelchair clearance dimensions: 49 CFR Part 38—Americans with Disabilities Act (ADA) Accessibility Specifications for Transportation Vehicles [https://www.ecfr.gov/current/title-49/subtitle-A/part-38/subpart-B], Subpart B—Buses, Vans and Systems, 38.23—Mobility aid accessibility. (c) Vehicle ramp—(2) Ramp surface.

9. FTA Transit Bus Mirror Configuration Pilot Project (Report 0219), VTTI Mirror Design Guide.

10. US DOT NHTSA Letter of clarification, Jonathan C. Morrison (Chief Counsel) June 4, 2020: “571-205-Driver Shield for Buses and Vans_final signed.pdf.”

11. FMVSS No. 217; Bus emergency exits and window retention and release.

12. FMVSS No. 111; Rear visibility.

13. 49 CFR 571.103 FMVSS Standard No. 103; Windshield defrosting and defogging systems.

14. SAE J381-JUN2020, Windshield Defrosting Systems Test Procedure and Performance Requirements—Trucks, Buses, and Multipurpose Vehicles.