Human Factors

"Human factors refer to environmental, organizational and job factors, and human and individual characteristics, which influence behavior at work in a way which can affect health and safety."

— Health and Safety Executive, 2009

Human factors, then, break down to three topics of concern:

  • what people are being asked to do (the task and its characteristics),
  • who is doing it (the individual and their competence), and
  • where they are working (the organization and its attributes).

Research has indicated that accidents usually occur for one of three principle reasons — perceptual error, mental distraction, or failed response. Perceptual error occurs when important information is below the threshold for observation, for example it was too dark or there was a glare. In other cases, the driver makes an error such a misjudging a curve radius or distance. The second reason is basically mental distraction. In this far more common cause, information is detectable but the driver is focused elsewhere. In the third explanation, the driver may correctly assess the information, but fail to choose the right response — or make the right decision but then fail to execute.

The study of human factors uses scientific knowledge of human capabilities, perception and attention, memory, and behavior to understand how people interact with the world. Human factors also include any associations with buildings, computers, medical or other electronic devices, vehicles, or other technology. Studying these elements helps create better environments, and examines the source of error in existing ones. The study of human error remains relevant because it occurs so frequently, and in all aspects of life. Almost all human interactions involve visual perception — the ability to recognize and assess, then act. Understanding how this happens is often the key to analyzing human choice and behavior, and to understanding accident and trademark confusion.

There are three main human failures (unsafe acts) that may lead to accidents. The first, error, is an unintended action that occurs during a routine task. The second, a mistake, involves a lapse in decision-making. The third, a violation, is an intentional act of wrongdoing.

How often a human failure will occur is determined by performance influencing factors, such as competence, morale, noise levels, distraction, time pressure, workload, and communication systems. Because these performance factors can be tracked, assessed, and managed, it is possible to predict and control human failure relatively well.

A comprehensive study of road safety found that human error was the sole cause in 57 percent of all accidents and was a contributing factor in over 90 percent. In contrast, only 2.4 percent were due solely to mechanical fault and only 4.7 percent were caused only by environmental factors. Other studies have reported similar results.

Buettner, R. and W. Rashbaum. 2008. “Criminal Inquiry Is Opened in New York Crane Collapse. The New York Times. http://www.nytimes.com/2008/06/01/nyregion/01collapse.html.

Friess, S. 2005. “Laptop design can be a pain in the posture”. USA Today. http://www.usatoday.com/tech/news/2005-04-12-laptop-pain_x.htm.

Health and Safety Executive. 2009. “Human factors and ergonomics”. http://www.hse.gov.uk/humanfactors.

Pasztor, A. and S. Carey. 2008. “Pilot Fatigue Spurs Calls for New Safeguards”. The Wall Street Journal.
http://online.wsj.com/article/SB122117729872125851.html.