Case Studies:

Physical ergonomic evaluation of any vehicle workstation starts with assessing key human factor issues e.g. spatial arrangement of driver’s/ passenger’s seats, reachability of  the occupants towards various controls (gear, accelerator, clutch, break , various knobs and switches etc.); force requirement for operating controls; comfort/ discomfort during driving or for sitting for long duration; visualization of displays/dials or controls inside vehicle; visibility towards road ahead or vision through rear view mirrors; ingress/ egress; various clearance dimensions (leg room, head room, lateral clearance etc.); environmental conditions (noise level, temperature, humidity etc.) and so on.

To evaluate anthropometric compatibility of the users (driver/passenger) with vehicle workstation components (seats, controls, displays, clearance spaces etc.), generally 5th percentile (for maximum dimensions), 50th percentile (for average dimension) and 95th percentile (for minimum dimensions) body dimensions of the targeted population are considered.  As a standard practice, 5th percentile adult female, 95th percentile adult male anthropometric value and 50th percentile adult pooled (combined male and female data) data from standard database are used for evaluation purposes. For example, minimum overhead clearance inside the vehicle should be more than 95th percentile male sitting/standing height as per requirement. Similarly, minimum seat width needs to be decided based on 95th percentile sitting hip breadth of females. On the other hand, maximum reach distance towards any control should be decided according to 5th percentile female reach dimension, so that anyone from the user population can easily access that control.

From the above discussion, it is clear that different percentile body dimensions need to be considered during evaluation of different design criteria following requirements.  Sometimes, it is stated that evaluation is performed with 5th percentile female or 95th percentile male but in reality there is not a single individual whose body dimensions are of a particular percentile value. For example, if height of a person is of 70th percentile value, his leg length may be of 50th percentile value. Hence, it is better to mention that evaluation is based on 5th /50th /9th percentile body dimensions.

To find any specific percentile (say, 5th percentile) dimensions of different body parts, actually large number of individuals would be required (because for a single individual different body parts are of different percentile values). Many instances, it is impossible to recruit large number of test subjects for evaluation. To solve this problem,  few individuals (male/female) are identified (from a target population) whose most of the body dimensions are close to a specific percentile (5th/95th) value and anthropometric compatibility evaluation is performed by them.

As discussed earlier that it is almost impossible to find any individual whose body dimensions of  a particular  percentile, various digital human modeling software  are used to develop manikin/human model with specific percentile anthropometric values for ergonomic evaluation of CAD model of the vehicle  in virtual environment.

Presently, vehicle manufacturers follow various standard recommended dimensions for their design. Standards provided by Society of Automotive Engineers (SAE Standards) are widely followed.

In the present module, one case study of ergonomic evaluation of a vehicle workstation with an individual in driver seat has been depicted to provide an idea of how a vehicle workstation can be evaluated for various human factor issues.

Note: 
Standard methods of evaluation with specific percentile anthropometric values to evaluate accommodation of entire population or their comfort have not been followed in this module. Only, anthropometric compatibility and other human factor issues have been evaluated for a specific vehicle and for an individual (not for population).

• Sitting Accommodation:


Observation:
All the seat dimensions (seat cushion depth, width and height, backrest with and height; head rest dimensions) were found acceptable. More over due to various adjustable features of the seat one can adjust backrest angle/position of headrest, position of seat etc. as per his/ her requirement.

• Sitting and Driving Comfort:


Observation:
Adopted driving posture by the individual shows that angles at various body joints are in comfort range as defined by Porter and Gyi (998 ).

The case study of a car from ford motor was done to verify the application of ergonomics.

Clearanace Dimensions:
• Headroom:


Observation:
The headroom for the vehicle is sufficient for uses to avoid head striking with roof during jolts/ jerks.

The case study of a car from ford motor was done to verify the application of ergonomics.

• Leg room:


Observation:
The legroom for the vehicle is sufficient for users for normal pedal operation.
There is no collision between:
• Seat front edge with popliteal area of lower leg,
• Thigh/knee with steering wheel/dashboard.

The case study of a car from ford motor was done to verify the application of ergonomics.

• Lateral Clearance:
 

Observation:
Left side and right side lateral clearance for the driver seat was found sufficient.

• Visual Field:

Vision towards displays and controls on dashboard.


Outside  front view through windshield.

Observation:
No visibility problem/ visual obstruction was found. The upper edge of the dashboard was low enough to see the road in front.