Human error causes an alarmingly high number
of mishaps. Between 50 and 75 percent of mishap
investigations conclude that the primary cause of the
mishap was human error. Human error findings
consider the human involvement before, during, and
after the mishap.
We can reduce the number of mishaps by learning
to identify and control the human factors that cause
mishaps. Human error is part of nearly every mishap.
Human error includes the actions of all personnel
involved in the mishap. It includes those personnel who
may have maintained or repaired equipment or even the
worker at the factory where a part was manufactured.
Human error involves both physical and mental factors,
such as the following:
Ergonomics (design of the workplace)
Physical strength and condition of the individual
Physical stresses and the bodys subsequent
Mental factors, including the persons attitude;
behavioral factors; ability to retain and assimilate
training; external mental stresses, such as inter-
personal relationships; and mental illnesses
All of us mentally process information we receive.
Factors such as personal experiences, emotions,
knowledge, motivation, and attitudes influence how we
interpret this information. They also cause us to respond
in various ways to different situations. When a mishap
occurs, we carefully examine each of these factors. Each
one can cause the best trained and most skilled worker
to make a wrong decision or response.
Ergonomics refers to the technology involved in
helping people physically adjust to their workplace. It is
also called biomechanics or the man-machine interface.
Basically, ergonomics concerns the design of a
workplace, space, or process to minimize stresses on the
body and to maximize production. Ergonomics became
important with the development of production lines that
required constant, repetitive motions.
A workbench that is too high or too low can cause
fatigue. Poor lighting can cause confusion. Emergency
switches that are out of reach can impair a person from
controlling them. All of these work area designs place
stress on the body that could contribute to human error.
Controls that an operator cannot reach quickly and
easily are examples of poor design. Other examples are
emergency controls protected by cumbersome
interlocks and displays that are difficult to read and
Poor functional layout within a space causes
inefficient operations and maintenance difficulties,
which breed jury-rigged shortcuts. When investigating
a mishap, we must look at the work area in which the
Temporary physical illnesses, such as colds, flu,
dizzy spells, heat stress, and nausea, affect our ability to
work safely. These disorders can cause physical
impairments that can contribute to mishaps. They can
also disrupt concentration, mental alertness, memory,
and reasoning ability.
Physical impairments, such as back injuries or
hernias, can make people susceptible to mishaps. The
weakened physical condition accompanying such
defects can impair strength, stamina, and agility.
Mishaps also can stem from two other types of
physical impairmentvisual and hearing. Good vision
is important to every job. A common visual impairment
such as faulty depth perception can cause mishaps such
as tripping or falling. Hearing impairments can cause
mishaps when persons cannot understand audible
communications and signals.
Alcohol is a chemical depressant. It acts as a general
anesthetic for those parts of the brain which suppress,
control, and inhibit thoughts, feelings, and actions.
Typical effects of alcohol consumption include
impaired judgment, unrealistic confidence, and slowed
coordination and performance. Such effects bring about
risk-taking behavior associated with unsafe acts and
Drug abuse causes many mishaps. Some people die
as a result of a drug overdose or respiratory depression
caused by barbiturate intoxication. Sailors high on
amphetamines and barbiturates sometimes fall