Ferrell’s Human Factors Theory

Ferrell’s Human Factors Theory n
Ferrell’s Human Factors Theory

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:

Ferrell’s Human Factors Theory

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:

  1. Overload (A mismatch of capacity, load and a state) due to-

(a)LoadTask (Physical information processing)
  Environment (Light, noise, distraction, stressors that require active coping)
  Internal (Worry, emotional stress)
  Situational (Ambiguity of goals or criteria, danger)
(b)CapacityNatural endowment, physical condition, state of mind, training, drugs, pollutants, pressure, fatigue, stressors that impair ability to respond
(c)StateMotivational level and arousal level


  1. Incompatibility (incorrect response or mismatch) due to –
(a)Stimulus ResponseDue to control – display
(b)Stimulus StimulusDue to inconsistent display types
(c)Response ResponseDue to inconsistent control types or locations
(d)Work stationSize, force, reach, feel


  1. 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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