Brazil Seat Ergonomics & Vibration Talk

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Driver Ergonomics and

Whole Body Vibration

Eckardt Johanning M.D. M.Sc.

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The problem – The Aching Back

• Risk analysis:

• Repetitive mechanical stress:

vibration and shock• Posture: Seat

• Exposure duration & break time: Schedule

• Health complaints/disorders and injuries

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Where do you find Vibration?

Hand-ArmWhole Body

In Buildings

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Tested yard switcher GP40-2 - January 27, 2004

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DEFINITION OF WHOLE BODY

VIBRATION

• Mechanical

v ibrat ion that, when

transm it ted to the

who le body , entai ls

r isks to the heal th

and safety o f

workers, inpart icular low er

back morb id i ty and

traum a of the sp ine.

Eckardt Johanning M.D. M.Sc.

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VIBRATION

• Began with the

Industrial Revolution.

• Humans exposed to

oscillatory motions

(vibration) for the firsttime when working

with powered

equipment.Eckardt Johanning M.D. M.Sc.

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WHAT IS SHOCK & VIBRATION?

Eckardt Johanning M.D. M.Sc.

Simples vibration

Two dominant frequencies

Complex vibrations:

multiple dominant frequencies

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WHAT IS SHOCK & VIBRATION?

Eckardt Johanning M.D. M.Sc.

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What is Whole Body

Vibration (WBV)?• Energy transmitted to the body as a whole,

through a supporting surface 

• Important Factors:

 – magnitude

 – direction

 – frequency

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Measuring Vibration

• Acceleration: measure of vibration

• Vibration: magnitude and direction

• Measurements: three directions:

 –  x, y, z

• Units: meters per second squared

(m/s2)

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Eckardt Johanning M.D. M.Sc.

The concept of Resonance effects: Magnification

Resonance is the tendency of a system to oscillate with larger amplitude at

some frequencies than at others.

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CRITICAL

RESONANCE

RANGES OF

THE HUMAN

BODY.Eckardt Johanning M.D. M.Sc.

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Vibration and Resonance Effects of Internal Organs of Humans

Eckardt Johanning M.D. M.Sc.

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Eckardt Johanning M.D. M.Sc.

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 AGINGCROSS

 ANATOMY &

MRI IMAGE

Eckardt Johanning M.D. M.Sc.

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Spine aging and vibration related

degenerationMore and earlier damage

Eckardt Johanning M.D. M.Sc.

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RISK FACTORS

Posture.

ExposureDuration.

RestPeriods.

Eckardt Johanning M.D. M.Sc.

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MTA test bus  – March 8, 2004

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TWU test driver  – WBV seat

test pad

Orion CNG Bus  – built 5/03 9938 miles  – 

Seat: Recaro air suspension (ergo-metro)

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Seat air suspension

adjustments

Problem: in extreme position  – suspension impaired

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MTA  – controls…. 

Seat back support

adjustment problem

 –restricted & hits

wall

MTA vibration

sensor

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The Seat of old New York City Buses

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Vertical Axis  – Seat levelTime Sample

t

hh:m

m:ss aweq  MTVV VDV

VDV/aw*T1/

4 

MTVV/awe

q  CF14:11:45 300 0:05:00 0.364 1.77 2.87 1.89 4.85 10.75

14:16:45 300 0:05:00 0.514 1.79 3.54 1.65 3.48 6.57

14:21:45 300 0:05:00 0.533 2.25 3.78 1.70 4.22 10.08

14:26:45 210 0:03:30 0.508 1.45 3.04 1.57 2.86 5.71

14:33:30 300 0:05:00 0.437 1.57 3.03 1.67 3.59 7.50

14:38:30 300 0:05:00 0.605 2.64 3.95 1.57 4.36 7.58

14:43:30 300 0:05:00 0.350 1.49 2.84 1.95 4.25 13.11

14:48:30 300 0:05:00 0.244 1.38 2.03 2.01 5.66 14.36

14:53:30 300 0:05:00 0.245 0.81 1.70 1.67 3.29 7.46

15:05:15 300 0:05:00 0.243 1.06 1.77 1.75 4.34 8.48

15:10:15 45 0:00:45 0.454 1.05 1.79 1.52 2.32 6.07

15:11:15 120 0:02:00 0.378 1.45 2.15 1.72 3.84 7.86

3075 0:51:15 0.42 2.64 5.59 1.79 6.28 12.79

Tri axial vibration bus (vs train) compared

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Tri-axial vibration bus (vs. train) compared(seat and floor) (ISO 2631, 1997)

Vibration (aw rms) (mean) :

Fore-aft (x) 0.21 (0.18) m/s2,

Lateral (y) 0.19 (0.28) m/s2Vertical (z) 0.42 (0.32) m/s2.

Frequent and high shock levels:

The Crest factors (CF): 9-16 (>9)

Maximum Transient Vibration Value (MTVV/aw):5.13  (5. 26) (x),

4.34  (5.12) (y)

6.28  (4.81) (z)

Vibration Dose Value (VDV/aw T 1/4) 

1.63  (1.32 to 2.3) (x-axis)1.7  (1.33 to 1.7) (y-axis)

1.79  (1.38 to 1.86) (z-axis)

Seat transmission factors (SEAT):

x:1.44 y:1.01 z:0.71  (1.44,1.2, 1)

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STANDARDS

Eckardt Johanning M.D. M.Sc.

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Summary and RxVibration and shock are recognized risk factors

for ergonomic stress and back disordersPreliminary and comparison testing of bus

operator seat shows that WBV are in asimilar range

New study of Railroad engineers reveals highlevel of back complaints and disorders

Transit workers study recommended based onpreliminary analysis of test data of “modelbus” 

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Summary and Rx

• Transit workers study

recommended based on preliminary

analysis of test data of “model bus” • Collaborative and participatory

principle

• Intervention study

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How Do We Control Exposure

to Whole Body Vibration ?u  Redesign or

engineering controls

u  Maintain seatingsystems

u  Administrative controls

u  Anti-vibration seatcushions

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Key Check Points  – 

Healthy Driving1. Seat adjustment (length)

2. Seat angle adjustment

3. Back support adjustment

4. Pedal angle adjustment

5. Seat height and pedal reach6. Knee angle (110-120 degree)

7. Leg/Thigh support easy

8. Steering wheel and

instruments (slightly angled

elbow)

9. Good back support without

pressure?

10. Head support (top above eye

level?)Eckardt Johanning M.D. M.Sc.

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New Generation Bus Seats• Suspension seat adjustment

1. Height

2. Lumbar support

3. Lateral support

4. Backrest

5. Heater/ventilation6. Armrest

7. Armrest adjustment

8. Seat pan angle

9. Seat depth adjust.10. Fore/aft adjust.

11. Swivel

12. Vertical shock

absorber adjust.

Eckardt Johanning M.D. M.Sc.

Source: Grammer, Germany

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•Change seatingposture frequently:

 – Dynamic sitting  – 

move and change

posture• Inform yourself about

the bus seat and

driver adjustments

• Sit slightly backwardswith good contact to

back support

Eckardt Johanning M D M Sc

Think of

yourback

Take a break and move around!

Good sitting posture!