Expert Article Library

Human Factors as a Field

by Dr. Richard J. Hornick

By Dr. Richard J. Hornick - Email:

The discipline of Human Factors offers an opportunity for attorneys to tap into a scientific field that is highly pertinent to a wide range of judicial matters, especially in workplace injury, product liability, personal injury, and transportation accidents. Human factors professionals (whether primarily practitioners, academicians, or researchers) have testified in plaintiff and defense matters and have successfully withstood Daubert-based motions to exclude their testimony.

Though having a variety of historical antecedents in behavioral and engineering sciences, the field of human factors is generally recognized to have its major impetus for growth during World War II as a direct result of the development of increasingly complex equipment and systems requiring a deeper understanding of human characteristics. Data were needed about human capabilities and limitations in order to increase the likelihood of safe and efficient operations in these systems. The field of experimental psychology provided the largest initial resource for that kind of information because of research conducted in areas such as vision, audition, perception,reaction time, information procession, decision-making, and capabilities in task performance.

Concurrently, industrial applications were developing in areas of personnel selection, training, motivation, inspection, and quality control. The term "ergonomics" is used as an adjunct to human factors and essentially is an equivalent term. However, ergonomics has been popularized such that much of the general population thinks of ergonomics as simply "comfort of office furniture" or "cumulative trauma disorder".

Today, the general goal of human factors specialists is to assure that the things that people use or maintain are designed in a manner to be most compatible with human capabilities and limitations in order to (a)reduce the probability of human error; (b) enhance system performance; (c) assure safety of anyone associated with the system or equipment. In designing small appliances, medical devices, high performance aircraft, transportation systems, manufacturing facilities and processes, office environments, or anything else, human factors professionals have demonstrated significant accomplishments in increasing human safety, comfort and productivity.

Representative Issues

This brief section is meant to be illustrative,not exhaustive, in order to suggest the kinds of issues human factors forensics practitioners may address. In any particular accident matter, of course, any of the various factors included below may become involved. In a machinery accident: task operations and procedures; skill requirements; type of guarding provided; controls and displays; training and experience; instructions; warnings; reach and muscle force;lighting and visibility; reaction time. In a product liability matter: anticipated user population; expectancies and experience; controls and displays; color coding; guarding;warnings; manuals; hidden dangers; integration with body characteristics. In a vehicular accident: visibility and lighting; traffic control devices; perception and reaction time;training and experience; fatigue; age; roadway characteristics; intersection and/or railroad crossing features. In a personal injury accident: (e.g., a trip and fall) --familiarity; visibility and lighting; placement of barricades; markings; warnings;handholds; railings.

Role of Human Error

Consider two aspects of "human error" -- pervasiveness and inducement. First, human error is involved in virtually any accident event. Most of us think of user or operator error (as in "pilot error" in an aviation accident)when hearing that term. However, human error can enter into an accident event in many other ways. During the design process, a design flaw may be introduced; in manufacture,assembly errors can occur; and during inspection, those defects may not be found because of human factors. A human factors specialist can provide understanding of the contributors to such errors at those different stages when they are important to the accident event.More importantly, human error is frequently "design induced". Studies have clearly shown that human errors are not just self-caused. Indeed, the design of controls,displays, workstation arrangement, guarding, instructional and warning label content, and environmental factors such as lighting or noise may elicit the error. Many tragic design-induced errors have been well documented. The tendency to dismiss an aviation accident, an air traffic control radar loss, a single vehicle fatality accident, and the like on "human error" is appropriately challenged in light of the fact that the design itself may promote human errors in the cockpit, in the factory, in a control room,or on a roadway. Here, the human factors specialist can play a pivotal role in understanding accident factors and interactions.


Human Factors is an established science and professional discipline.It provides a knowledge base for understanding the interaction of design with human capabilities and limitations. Those human characteristics are contained in several dimensions:

  • psychological -- e.g., cognitive skills, perception, reaction time, expectancies, information processing, decision making, motivation; stress;
  • physiological -- e.g., vision, audition, tactile sensations, fatigue;
  • anthropometric -- e.g., body size, reach, muscle strength.

Human factors data and criteria have been applied to the design of ordinary appliances, farm and construction machinery, transportation vehicles and systems, industrial equipment, office equipment, command and control rooms,and even to spacecraft. The major focus of the field is on the factors involved in"human error" and the implications for product design and system safety. An established database, a wealth of literature, notable journals, professional societies,and certification programs all attest to the validity of the field and its useful introduction into the forensics process.