Ferrell’s Human Factors Theory:
Dr. Russell Ferrell, Professor of Human Factors at the University of Arizona give this theory of accident causation as shown in diagram below:
This theory states that accidents are the result of a casual chain (as in multiple causation theory), one or more of the causes being human error, which is in turn caused by three situations – overload, incompatibility and improper activities. Factors affecting these three situations are as follows:
- Overload (A mismatch of capacity, load and a state) due to-
|(a)||Load||Task (Physical information processing)|
|Environment (Light, noise, distraction, stressors that require active coping)|
|Internal (Worry, emotional stress)|
|Situational (Ambiguity of goals or criteria, danger)|
|(b)||Capacity||Natural endowment, physical condition, state of mind, training, drugs, pollutants, pressure, fatigue, stressors that impair ability to respond|
|(c)||State||Motivational level and arousal level|
- Incompatibility (incorrect response or mismatch) due to –
|(a)||Stimulus Response||Due to control – display|
|(b)||Stimulus Stimulus||Due to inconsistent display types|
|(c)||Response Response||Due to inconsistent control types or locations|
|(d)||Work station||Size, force, reach, feel|
- Improper Activities due to-
- The worker did not know how to do it.
- He deliberately took risk due to
- Low perceived probability of accident
- Low perceived cost of accident
Since this is basically human factor model greater emphasis is placed on the first two causes of human error, overload and incompatibility.
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