Human Factors

Injury producing accidents involve an interaction between humans and physical, inanimate objects, or between humans and animals. The physical, inanimate world is usually the focus because the physical events can be modeled reasonably accurately by applying the laws and concepts of physics.

The human aspects are all too often ignored, other than possibly a casual mention of  “an accepted Perception – Reaction time” which may be grossly in error for a particular event. In part ignoring the human elements is often due to the fact that many, if not most, aspects of the human factors are “fuzzy” rather than clearly mathematically definable. However, to ignore the human factors involved is frequently to ignore the real crux of the case.

HUMAN FACTORS are those aspects which describe the aspects of a human being, human experience, and human behavior.


  • Psychological & Physiological Elements:
    • Perception Reaction Times and variability under different environmental conditions
    • Recognition or perception of a hazard or potential hazard
    • Cognition
    • Influence of experience and training on task performance
    • Effects of age on performance
    • Effects of various diseases on performance
    • Effects of illumination, glare, and shadows on vision, detection and discernibility of an object
    • Psychological elements of  the senses (vision, smell, taste, touch, and hearing) on task performance
    • Influence of body build and posture on task performance
    • Elements involved in the perception of safety vs perception of risk
    • Visibility,  comprehensibility, clarity, and adequacy of signs, warnings, and directions
    • Differences between Day vision and night vision
  • Anthropomorphic Elements as a Sub-set of Human Factors:
    • Length of body segments as a function of total height
    • Weight distribution in body segments relative to total weight
    • Maximum predicted walking speed as a function of total body height
    • Goodness of fit of the body to vehicles, equipment, machines, and the task environment
    • Range of height or weight for different ages in children and adults
    • Expected reach (arm or leg) given a total body height and weight
    • Determination of total height from the length of an arm or leg – often important in determining who was the driver in a vehicle accident