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HUMAN FACTORS

ERROR INVESTIGATION

EXERCISES

HUMAN ERROR

THE POTENTIAL FOR HUMAN ERROR

The study of human factors is very much concerned with identifying those aspects of

behaviour that result in people making mistakes or errors, some of which could result in

accidents or incidents of various kinds. Limitations in human capacity to perceive, attend to,

remember, process and act on information are all relevant in the context of human error.

The HSEs publication, Human factors and industrial safety !HS!"#$%, &'%'#, identifies a

number of factors that can contribute to human error and the resulting accidents. These

include the following.

i# Inadequate information (eople do not make errors merely because they are

careless or inattentive. )ften they have understandable !albeit incorrect#

reasons for acting in the way they did. )ne common reason is ignorance of

the production processes in which they are involved and of the potential

conse*uences of their actions.

ii# Lack of understanding This often arises as a result of a failure to

communicate accurately and fully the stages of a process that an item has been

through. +s a result, people make presumptions that certain actions have been

taken when this is not the case.

iii# Inadequate design esigners of plant, processes or systems of work must

always take into account human fallibility and never presume that those who

operate or maintain plant or systems have a full and continuous appreciation of

their essential features. -ndeed, failure to consider such matters is, itself, an

aspect of human error.

here it cannot be entirely eliminated, error must be made evident or difficult.

/ompliance with safety precautions must be made easy. +de*uate

information as to ha0ards must be provided. Systems should fail safe. that is,refuse to produce in unsafe modes of operation.

iv# Lapses of attention The individuals intentions and ob1ectives are correct and

the proper course of action is selected, but a slip occurs in performing it. This

may be due to competing demands or !limited# attention. (aradoxically,

highly skilled performers, because they depend on finely tuned allocation of

their attention, to avoid having to think carefully about every minor detail,

may be more likely to make a slip.

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v# Mistaken actions This is the classic situation of doing the wrong thing under

the impression that they are right. 2or example, the individual knows what

needs to be done, but chooses an inappropriate method to achieve it.

vi# Misperceptions 3isperceptions tend to occur when an individuals limited

capacity to give attention to competing information under stress produces

tunnel vision or when a preconceived diagnosis blocks out sources of

inconsistent information. There is a strong tendency to assume that an

established pattern holds good so long as most of the indications are to that

effect, even if there is an unexpected indication to the contrary. )ne potent

source of error in such situations is an inability to analyse and reconcile

conflicting evidence deriving from an imperfect understanding of the process

itself or of the meaning conveyed by instruments. 2ull analysis of the

preventative measures re*uired involves the need for people to understand theprocess as well as technical and ergonomic considerations concerned with

instrumentation.

CAUSES OF ERRORS

There are a multitude of factors which can and will contribute to errors being committed4

Here are some of them4

i# Stress

ii# 2atigue

iii# /omplacency

iv# /ommunication

v# -gnorance

e shall address the more common, easily recognisable ones but, be aware that around every

corner a new one is waiting to trap the unwary.

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HUMAN FACTORS

ERROR INVESTIGATION

EXERCISES

STRESS

w Sickness absence costs to UK economy on averae !""#$$$#$$$#$$$

w %$ & '$( o) t*is is stress re+ate,

-C./.I. "00'1

w ALCOHOLISMcosts over !2.2 bi++ion 3er year in terms o) 3remat4re ,eat*#

sickness absence# 4nem3+oyment an, N.H.S. treatment

STRESS

5*at is Stress6

-t has been said that stress is a reality like love and electricity 5 unmistakable in experience

but hard to define6 7esearch has shown what stress is not

i# Stress is not nervous tension

ii# Stress is not the discharge of hormones from the adrenal glands !the common

association with adrenaline and stress is not totally false but the two are only

indirectly associated#

iii# Stress is not simply the influence of some negative occurrence 5 stress can be

caused by *uite ordinary, even positive events, such as a passionate kiss

iv# Stress is not entirely a bad event8 we all need a certain amount of stimulation

in life and most people thrive on a certain amount of stress

v# Stress does not cause the bodys alarm reaction which is the most common useof the expression 5 what causes stress is a Stressor

&. OCCUPATIONAL STRESSORS

3ost is not all of us will recognise and readily relate to the following list of stress

factors4

i1 NE5 5ORK PATTERNS

ii1 NE5 TECHNOLO78

iii1 PROMOTION


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HUMAN FACTORSERROR INVESTIGATION EXERCISiv1 RELOCATION

v1 9ERE7ULATION

vi1 9O5N SI:IN7

vii1 ;O/ 9ESI7N

viii1 /ORE9OM

i

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v# hat is the worst thing that can happen to me;

Listen to your rational mind

vi# Has this happened before and what can - do better;

vii# hat is the best rational plan

+ct

viii# Speak up and ask for help or extra time as re*uired

)ften the error of pressure is due to an error of not communicating properly and

trying to make do.

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HUMAN FACTORSERROR INVESTIGATION EXERCISThe error of complacency can be lessened by4

i# +lways following the checklist or work sheet4 ie dont attempt to do

work from memory.

ii# =e aware of the danger of complacency and tell yourself4 :Today - amgoing to find a crack: or whatever.

A@arenessis your strongest advocate in preventing complacency.

>. 9ISTRACTION

Meanin4

9ra@ ones attention a@ay# Con)4se

istractions are a common occurrence anyway yet, if they occur in a critical phase of

our work, they can have disastrous conse*uences. istraction is one of the main

reasons that an engineer fails to secure ?@T :=: or a control cable or other critical

part. (sychologists say it is the number one cause of forgetting. )ften after an error

has occurred, the engineer will be at a loss to explain how it happened. -f other

factors are present such as fatigue and stress, then the likelihood of an error occurring

increases.

(revention consists of awareness of the problem and the use of safety nets such as4

i# proper use of detailed check lists

ii# flagging incomplete work

iii# witness marks

iv# dual or independent inspection

v# going back three steps, ie return to a :known: point in the procedure.

A. FATI7UE

2atigue is the bodys normal reaction to a physical or mental stress of prolonged

duration. -ts onset is insidious and the symptoms are not always recognised until the

person has reached a high degree of fatigue. There are two types of fatigue4

A.& Ac4te Fati4eB

is the result of intense physical or mental activity at a single task. -t is of shortduration, measured in hours, and is cured with agoodnights sleep.


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HUMAN FACTORS

ERROR INVESTIGATION

EXERCISESA.9 C*ronic Fati4eB

is caused over a period of time and takes much longer to recover from. Each person has a

personal level of ability to withstand fatigue which slowly diminishes as the person ages.

A.< Ca4ses o) Fati4eB

Some of the things that can induce fatigue are4

i# Lon *o4rs o) +abo4rof any type, physical or mental, but the harder

the labour, the sooner the fatigue.

ii# Lack o) s+ee3due to time to or inability to, sleep. -f one can not sleep,

it likely is due to stress, but physiological factors can play a role. (ain

due to sickness or in1ury or simply a disruption of ones circadium

rhythm ie 1et lag.

iii# Stressof high intensity andBor long duration will induce fatigue.

iv# Lare tem3erat4re variations#hot or cold, will induce fatigue.

Temperatures in excess of 'C deg 2 !C deg 2 !&C/# without proper clothing, can

lead to hypothermia.

v# Noiseif above the %C d= mark for long duration will cause fatigue.

Exposure to loud noises without proper hearing protection is a self

correcting problem because, in time, you will no longer hear the noise

!or any other noise# and the damage cannot be reversed.

vi# >ibrationcan also cause fatigue. -f for prolonged periods and of

sufficient intensity, it will cause headaches and muscle discomfort.

However unlike noise, vibration is not known to cause any permanent

damage although :white hand: from chain saw vibration and rivet guns

can become permanent if ignored long enough.

vii# Stron Li*tinand to a lesser degree, poor lighting will contribute to

fatigue. The normal symptom is a headache, and if bad or long

enough, eyestrain.

A.$ Sym3toms o) Fati4re

=ecause the symptoms come on slowly it is important that we come to

recognise the symptoms and be aware of its effects. )ften the fatigued person

is unaware that he is fatigued until the symptoms and effects have become

*uite extreme, therefore4

i# An En*ance, Stim4+4s is re4ire, in or,er to res3on,.

The person would re*uire a larger crack in order to see it. The

greater the fatigue, the greater the stimulus re*uired.


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ii# Attention is re,4ce,

The person begins to overlook basic task elements.

The person becomes preoccupied with a single task to the

exclusion of others.The person begins to lessen his visual scan.

The person becomes less aware of poor performance.

iii# Memory is ,iminis*e,

The person begins to have inaccurate recall.

The person forgets peripheral tasks.

The person begins to revert to :old: habits.

iv# Moo, becomes @it*,ra@n

The person becomes less likely to converse.

The person becomes less likely to perform low demand tasks.

The person becomes more distracted by discomfort.

The person becomes more irritable.

The person begins to develop a :dont care: attitude.

(ersons who work a midnight shift should be particularly aware of the

symptoms as most persons have a normal low !circadian rhythm5time of day

effect# between CCC.

2atigue, as seen by its detrimental effects, can easily lead to a maintenance error, especially if

the person isnt aware he is suffering from it.

D. SHIFT 5ORK

Have you ever noticed how some people seem to bree0e through shiftwork with little

difficulty while others have a hard time; There are certain individual differences that

have been shown to cause these different reactions to shiftwork. Even if you dont

work on shifts, you might find that the information is useful anyway since we all

occasionally experience the sleepless night or stressful day not unlike that

experienced by shiftworkers.

+pproximately 9

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EXERCISES

Founger people apparently handle the physical demands of shiftwork better,

but older workers handle the social and interpersonal problems more

effectively, and extroverted, outgoing people seem to adapt more easily to

shiftwork than introverted types. The remainder of this section will look at

techni*ues that can be used by anyone, regardless of age or personality type,to help improve the *uality of sleep and reduce fatigue.

D.9 T*e Ro+e o) S+ee3

+lthough the role of sleep is not fully known, it is generally agreed that sleep

is not necessarily a passive state. there are a number of things that happen

during sleep that do not seem to happen when we are awake. 2or example,

body temperature, breath rate, heart rate, and blood pressure all drop duringsleep, while the secretion of human growth hormone and other anabolic

hormones !hormones that are involved in the cell building process# seem to

increase.

Thus the role of sleep may be to serve a rebuilding function by restoring

certain en0ymes and chemicals needed in our bodies. However, it is possible

that not all of sleep is necessary for restoration. Sleep researcher Games Horne

suggests that there are two sleep drives, the first being :obligatory: sleep

comprising the first five hours or so. The second sleep drive is :facultative:

and probably serves to pass time during the early morning hours when there is

nothing to do anyway.

-n other words, Horne suggests that if we normally sleep eight hours then the

last three hours of sleep really only pass time. The main work of sleep is done

after approximately five hours. so even if we dont get a full nights sleep,

chances are we are getting enough to recharge our systems.

3any of us who experience sleep deprivation on a continuous basis, however,

might not agree. 2ive hours sleep per night does not seem to be enough,

especially if we usually sleep longer. e could, as Horne suggests, practise

getting by with only five or six hours of sleep per night, but once we establisha pattern of sleep, it is often hard to break.

D.< P*ysica+ Fitness

(hysically fit individuals adapt to shiftwork better for a number of reasons4

they can handle the physical demands of shiftwork better, and regular

physical exercise promotes better sleepand helps to manage stress.

7emember that fitness activities can be anything from running marathons to

gardening, depending upon your interests and experience. Even low levels of

physical fitness seem to promote better health, which in turn can combat someof the negative effects of shiftwork.


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%. RESOURCES

7esources, or more appropriately the lack of resources have been the cause of many

an accident. Engineers are notorious for making do with less than ade*uate resources.

The lack of up to date manuals can cause and error especially in these rapidlychanging times and how often does an engineer have to make difficult decisions due

to the lack of materials. -n difficult times, lack of material may lead to an engineer to

let something go a little longer, against his better 1udgement.

Sometimes the resource needed is an expensive special tool that is seldom used.

ork is carried out without the proper tool and can cause a maintenance error if it is

not done properly. There have been cases where the person who can procure the tool

is unaware that it is even re*uired. an engineer was heard to say :- asked for the tool

two years ago and - still havent got it:, while the (roduction irector wasnt aware

that the re*uest was ever made.

)ne of the most common lack of resources is ade*uate lighting for their task in hand.

Engineers often depend heavily on flashlights perched on some part of the aircraft to

carry out a task when only a few meters away is a proper portable light.

Some facilities, especially as we move north, have woefully inade*uate heat in winter.

-t is easy to make a mistake when you are cold and miserable and all your

subconscious is thinking about is getting warm.

o not be afraid to ask for help when needed and ensure that you have done

everything you can to obtain the necessary resources.

'. COMMUNICATION

3E+?-?"4

T*e e

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EXERCISES'.< 9oB

i# +sk *uestions

ii# (araphrase

iii# 3ake eye contact

iv# @se positive body language

'.$ THIS IS COMMUNICATION6

- have to tell you that

what you heard and

what - said are

two different things andthat what you think

- said is definitively

not what - meant.

THE SECRET TO 7OO9 COMMUNICATION

Fou have

9 Ears

9 Eyes

" Mo4t*

>

Use t*em in t*at or,er an, 3ro3ortion.


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HUMAN FACTORSERROR INVESTIGATION EXERCIS&C. LACK OF KNO5LE97E

-n these times of ever changing technology, it is not difficult to come upon a task

which you lack the knowledge. To counteract this, aircraft companies attempt to

provide the correct amount of detail to their manuals or workcards without boring you

with complacency.

The key to the :lack of knowledge: error is to understand each step of what you are

doing, or talk to someone who does. Technical reps are paid good money to keep you

out of trouble.

-f its new, dont be afraid to ask. ont learn by mistakes and remember 3urphys

Law if you have any doubts.

M4r3*ys +a@

5 I) t*ere is a @ron @ay to ,o it# t*ats t*e @ay yo4++ ,o it.

THIS PA7E INTENTIONALL8 LEFT /LANK


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