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Bus design & safety
ACCORDING TO SPECIFIC KENYAN REQUIREMENTS:
LEGAL BACKGROUND (The Traffic Act & KEBS bus standard),
AVAILABILITY OF MATERIALS & TECHNOLOGIES,
ROAD CONDITIONS
Guide lines for Design:
Passenger safety
Staff safety
Traffic safety
Functionality
Aerodynamic
Ergonomy = Comfort
Presented by Ralph Hruschka MSc.
Inventor & Consultant at KVM Ltd.
“Never design
appearance only”
Safety critical features
1) Roll over protection, 2) Front impact protection, 3)Side impact protection, 4) Passenger door, 5) Door
hinge cover, 6) Passenger seats, 7) Seat mounting, 8) Front grille, 9) Gangway, 10) Cross members, 11)
Side wall diagonals, 12) X-Members, 13) Door grab handles, 14) Uppermost stair, 15) Door locking
mechanism, 16) Front bumper, 17) Rear bumper, 18)Rear overhang, 19) Rear glass / emergency exit
Moto: Every feature that will save a life must be realized
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Case 1: Roll over accidents
Roof collapsed and disintegrated
without safety concept
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Roll over protection
• To reinforce the strength in between side walls and the roof
• Prevention of a passenger cabin collapse sideward
Gussets
Diagonals
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Case 2: Front impact accidents
All pillars collapse forward
– roof disintegrated without safety concept
The roof will move
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Front impact protection
Option 1: Diagonal column to stabilize the roof thru directing the impulse force into the lower body:
•
Column out of two strong tubes
•
Zig-zag interconnection in between bars
•
Correct angle from roof to column
•
Correct angle from column into body
Stabilizing column
Impulse force
diverted into body
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Front impact protection
Option 2: Stabilize the roof thru reinforced pillars
Roof
Fixed side glass
Sliding side glass
Stabilized side pillars
Disadvantage: reduces size of glasses
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Case 3: Side impact accidents
Whole body bent & side wall collapsed without safety concept
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Side impact protection
•
Option 1: triangular vertical reinforcement inside legroom
Side reinforcement
triangular in legroom
Side reinforcement
triangular
No reinforcement at
floor mounting
Disadvantage: disturbing in the legroom
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Side impact protection
•
Option 2 (recommended): triangular vertical reinforcement underneath floor
Side reinforcement triangular
underneath floor
Gives structural strength against side impact and roll over
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Side impact protection
•
Option 3 (recommended): triangular reinforcement longitudinal inside floor level
View from above
Cross member
Impact force
Cross member
Side bent thru impact
without reinforcement
Side reinforcement
triangular longitudinal
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Number of cross members
•
•
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Enough for strength and safety according to load class (min. 4 for 26-seater, max. 8 for 71-seater)
Not more than necessary – weight and cost relevant
Welding joints fist grade and verified
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Gangway and seat arrangement
•
Width of gangway recommended is 450 mm (Class IV, above 40 passengers)
and 350 mm (Class III, 26 – 40 passengers)
This requires for 3X2 seat arrangement a vehicle track width of 2250 mm or correctly
curved side pillars
Gangway 450 mm
2 Seats = 800 mm
Side wall 50 mm
3 Seats = 1200 mm
Side wall 50 mm
150 mm maximum
150 mm maximum
Track width 2250 mm
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Side wall diagonal setting
•
•
Structural strength against rattling, cracks and bending
Prevent share force in an accident
Wrong: cutting share force
Correct: prevent share force
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Passenger door
Dimensions according to KEBS:
• Minimum height 1650 mm
• Minimum width 650 mm above 700 mm
• 1st step height maximum 460 mm above ground
Function according to European Safety regulations:
• In case of a panic after an accident the passengers want to press outward
• The passenger door must swing outward otherwise it becomes a death trap
Death trap
inward
swing door
Outward
swing door
Outward
sliding door
or
pantographic
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Door hinges
•
•
Protruding hinges like at the drivers door must have a cover to protect against
sharp corners
Passers by on foot or passing vehicles will be cut by sharp corners
Option 1: Hinge cover
Option 2: Hidden hinges
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Door grab handles
•
•
Safety for passing persons and traffic
Damage prevention
Groove mounting
Original CKD
Dangerous protrusion
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Uppermost stair
•
Uppermost stair not protruding into gangway
Dangerous interference
No interference
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Door locking mechanism
•
Not protruding into door aperture
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Passenger seats safety
•
•
•
•
No sharp corners
No protrusions
Made out of round tubes
Width of seat frame 400 mm
per seat
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Seat mounting
•
•
Strength increased thru short lever and additional stiffness
Seat anchoring forward and sideward stronger
Side mounting:
additional
strength
Long lever
Short lever
Floor mounting
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Passenger seats comfort
•
•
•
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Dimensions
Seat rest height & inclination
Seat base height & inclination
Head rest cover
Legroom
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Front grille
•
•
Loose grille gets lost if not ALLWAYS locked and will endanger traffic
Front grille must be fixed to body thru hinges
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Front bumper
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•
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Prevention of damages thru road conditions
Creating sufficient air flow to radiator
Access to towing hook
Rounded curvature to support comfortable handling
No sharp corners to prevent accidents
Original CKD bumper
Formula:
r(fr)+x(fr)[mm/m]
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Rear bumper
•
•
•
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Prevention of damages thru road conditions
Access to towing hook
Rounded curvature to support comfortable handling
No sharp corners to prevent accidents
Formula:
r(re)+x(re)[mm/m]
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Rear overhang
•
To ensure comfortable vehicle handling (stability on the road) the rear overhang
can be maximum:
60 % of wheel base measured behind rear axle to rear bumper
wheel base
60% of wheel base
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Rear glass / Emergency exit
•
•
•
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Access & size according to legal regulations
Safe opening function
Cost saving shape
Recommended flat to save costs
Unnecessary waste of
material and money –
very difficult to replace
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Functional bus design
Part 2: FUNCTIONAL features
20) Hump, 21) Windscreen, 22) Number plate provision, 23) Passenger door position 24) Side glasses
Hump
•
•
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Only small vehicles can be built like Formula 1 cars
Big vehicles require specific aerodynamic shape to reduce air resistance
Lower air resistance will reduce fuel consumption
Eddies at sharp corners
increase air resistance
Front hump eliminates eddies
Joint at
roof
bow
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Windscreen
•
•
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Cost reduction – recommended laminated, two piece flat glasses
Reduction of braking thru stones – high lower end
Reduction of heat – low upper end
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Number plate provision
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To accommodate square & long type
Protection of number plate lamp – no protrusions
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Passenger door position
•
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1st step height 460 mm maximum – recommended behind front axle
Creating space for air duct :
– Air duct is disturbing in leg room
– Shortest way for air intake required
– Vibration buffing in between engine and body
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Driver door
•
•
Dimensions similar to CKD
Avoid additional weight and stress to the hinges
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Comfort in bus design
Part 3: ERGONOMY = COMFORT features
25) Tool box, 26) Parcel rack, 27) Leg room 28) Arm rest, 29) Rearmost seat row
Rearmost seat row
•
Maximize leg room thru:
Side view
- Inclination of rear body backward
- Seat rest of rearmost row to fit into shape of rear body
View from above
Lost space
Inclination of rear body backward
Seat rest fit into body shape
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