1. Introduction to Accidents
(Module 1)

2. Definitions of an Accident
An accident is an unintended, unplanned single
or multiple event sequence that is caused by
unsafe acts, unsafe conditions or both and may
result in immediate or delayed undesirable effects.
(Brauer 1994)
因不安全行為與不安全狀況單獨或協同作用所
造成之單次或多次無意、未經策劃的一連串事件，
而導致立即或延遲發生的不樂影響。

3. To the safety specialist, every accident has one
or more identifiable causes. Chance may play
a role in bringing causes together.
There are two fundamental types of accident
causes: a. unsafe acts
b. unsafe condition
Accident involve either of these two causes or both.
Recognizing that accidents are caused and not
just functions of chance allows one to pursue
accident prevention. Some safety specialist
replace the term of “accident” to “incidence”.

4. Accidents tend to have a range of potential adverse
consequences:
Likely Consequences Example
1. A hazardous An operator activates a tagged
situation out piece of equipment. The
technician working on the
equipment is at lunch.
2. Near miss An employee slips in an oil
spill but recovers her balance.

5. Likely Consequences Example
3. Property The tines of a forklift pierce a
damage carton, destroying the
product within it.
4. Minor injury Carpenter hit his thumb with
a hammer.
5. Serious injury Employee's arm is caught by
conveyor belt, dragging the
arm to a roller and breaking
his arm.

6. Most accidents do not include injury or significant
loss.
Heinrich's Injury Pyramid

7. Heinrich's Injury Pyramid
The variation in accident consequences was
recognized early this century by Heinrich (1931)
with his injury pyramid.
These figures relate to a group of 330 similar
accidents. They demonstrate the degree of
variation involved with one type of hazard.
They should not be considered to be definitive.
Other authors, such as Heinrich, Petersen and
Roos (1980) and Hoyos and Zimolong (1988),
quote different ratios.

8. Inverted Reporting Pyramid

9. Inverted Reporting Pyramid
We are rarely able to measure the number of
accidents that actually occur. We measure
the number of accidents that are reported.
In general, the less severe the resultant injury,
the less likely it will be reported.
Alongside Heinrich's "injury pyramid" there
therefore exists an inverted "reporting pyramid".
For every near miss that is reported, there are
hundreds to thousands of lost time injuries that
are reported.

10. Type of loses Losses from accidents can take many forms, including:
Human: loss of time, medical services,
hospitalization, rehabilitation.
Materials(物): damage to property, equipment
and materials(物料).
Others: travel, record keeping, investigation,
clean-up, legal services, loss of production
and sales, loss of public image.

11. Severity of Consequences (loss)
The severity of the consequences will depend upon
factors such as:
1. the nature of the hazard;
2. the quantity of hazard involved (eg. airborne
concentration of solvent, kinetic energy of flying
object);
3. the duration of contact or exposure;
4. part of body affected; and
5. important factors unrelated to the hazard itself,
eg, luck and individual factors.

12. Direct versus indirect costs
Direct costs typically include medical expenses
and compensation paid to an injured employee
for time away from work and costs
for repair or replacement of damaged items.
Indirect costs are real expenses associated with
accidents, but difficult to assess for an
individual case.

13. Based on his own investigation in 1926,
Heinrich introduced the “4 : 1 ratio,” which
suggests that the total cost associated with
accidents is much higher than the obvious,
direct expenses.
Although the ratio varies for different companies
and different types of operations, the basic idea
is sound.

14. Unsafe acts and unsafe conditions
Heinrich analyzed 75,000 accidents and found
that 88% were caused by unsafe acts, 10% from
unsafe conditions and 2% from unpreventable
causes. This is Heinrich’s 88:10:2 ratio.
Engineers not only have many opportunities to
eliminate or reduce unsafe conditions, but also
have many opportunities to minimize unsafe acts.
Design that reflect and understanding of human
error and behavior can limit the range of human
behavior that leads to or causes accidents.

15. Accident - cost relationships
Gordon Lembke recognizes that costs are
unequally distributed for similar accidents.
For a group of similar accidents resulting in
injuries and direct costs (insurance claims), only
a small percentage of the injuries account for
most of the total costs of the group and a majority
of the injuries account for merely a small portion
of the total injury cost.

17. Theories of Accident Causes
1. Domino Theory (骨牌理論）
2. Energy Theory（能量理論）
3. Single Factor Theory (單因子理論）
4. Multiple Factor Theory （多因子理論）
5. Psychological/Behavioral Accident Causation
Theories (心理/行為理論）

18. Domino Theories There are three different domino theories of
accident causation:
Heinrich’s
Bird and Loftus’, and
Marcum’s Domino Theories.

19. Each domino theory presents a different
explanation for the cause of accidents,
however, each theory is predicated on the fact
that there are three phases to any accident.
The three phases are the pre-contact
phase, the contact phase and the post contact
phase.

20. The pre-contact phase are the events or
conditions that lead up to the accident.
The contact phase is the phase when the
accident actually occurs.The post-contact phase
refers to the results of the accident.
Domino theories represent accidents as causal
factors or hazard events. Each causal factor
affects the others if allowed to build up over
time (pre-contact phase). Without intervention,
the hazards will interact to cause the accident
and move into the contact phase. Thus the
derivation of the theory’s name as Domino.

21. Heinrich’s Domino Theory
Heinrich’s domino theory essentially states that
there are five series factors that could influence
an accident. The factors occur sequentially and
consist of the following:
A negative trait or factor is present in a person
as a result of social influence of environment
2. The negative trait or factor may lead to an
unsafe practice or condition

22. 3. The unsafe practice results in an unsafe
condition, or it results in mechanical or
physical hazards that are the direct cause
of an accident
4. Accidents that result from the above process
are typically the result of falls or impacts with
other moving objects

23. 5. Injuries from above are usually of the form
of lacerations and fractures. As a result of
this process, intervention or elimination of
any of the first four factors will stop the
injury or loss.

24. Bird and Loftus’ Domino Theory
series factors that could influence an accident.
However, this theory states that the ultimate
responsibility for the welfare of the employees
Lie with the management of an organization.
It is the manager of the organization who can
instill the controls necessary to prevent the
initiation of the domino effect.

26. Lack of Control – Management
Control in this instance refers to the four
functions of a manager:
planning, organizing, leading and controlling.
Examples of this domino are purchasing
substandard equipment or tools, not providing
adequate training, or failing to install adequate
Engineering controls.

27. 2. Basic Cause(s) - Origin(s)
The basic causes are frequently classified into a
personal factors group and a job factors group.
Personal factors may be lack of knowledge or
skill, improper motivation, and physical or
Mental problems; job factors include inadequate
work standards, inadequate design or
maintenance, abnormal tool or equipment wear
and tear, and abnormal tool usage.

28. 3. Immediate Cause(s) - Symptoms.
The primary symptoms of all incidents are
unsafe acts and unsafe conditions.

29. An undesired event occurs. The accidents are
4. Incident – Contact
An undesired event occurs. The accidents are
often represented by the eleven accident types,
Including:
stuck-by, caught-in, fall-to-below
struck-against, caught-on, overexertion
contact-by, caught-between, exposure
contact-with, foot-level-fall
(source: ANSI Z 16.2)

30. 5. People – Property – Loss
Result of the accident. The effects are property
or environment damage or injury to personnel.

31. Marcum’s Domino Theory
According to C. E. Marcum’s 1978 Seven Domino
Sequence of Misactsidents, a misactsident is an
identifiable sequence of misacts associated with
inadequate task preparation which could lead to
substandard performance and miscompensated
risks.

32. Marcum also includes the cost aspect of a loss.
Like the previous theory, Marcum states that
management is ultimately responsible to ensure
that the workplace is designed with adequate
controls to protect employee.
His seven domino sequences are:
Inadequate preparation
Substandard performance
Mis-compensated risk(s)
Harmful contact incident

33. Adverse reaction
Sustained losses
Incurred costs
Through this domino theory, Marcum shows that
accidents can be prevented by the management
by properly training the employees as well as
designing adequate controls into the work
process.

34. The Three Stages of Lost Control

35. Pre-Contact Stage: At this stage, management should be
concerned with issues such as engineering
practices in the design of new or modified
facilities, purchasing practices in the
procurement of new materials and equipment,
and the development of work standards that
could have loss potential implications.

36. The supervisor’s application of personal
motivation practices, job indoctrination,
standard job procedures, proper instruction,
and the use and enforcement of rules in the
work areas are elements in the pre-contact
stage that may actually prevent the first
domino from falling.

37. Contact stage It is important that management require the
reporting of all non-loss incidents or
“near misses” in order to implement
appropriate corrective action before repetitive
incidents occur that could have loss results.

38. Post -Contact Stage Emergency response
The availability and immediate provision of
emergency care has proven time and again to
be an effective measure to reduce the frequency
of death and disability.
Personnel should be trained and ready to cope
with all types of potential emergencies that
could arise in their work environments.

39. Rehabilitation Injured workers can remain off the job for
quite extended periods of time.
A management policy that focuses on
rehabilitation of the injured worker into
other jobs or tasks will retain the employee’s
intrinsic value to the organization while
reducing the overall loss resulting from an
accident.

40. Prompt repair actions There are many occasions where prompt
maintenance and repair of equipment can
reduce the potential for greater loss or
damage to property. Management should be
alert for any evidence of property damage
or premature wear-out of equipment. Small
cracks in machines, equipment, or building
structures can frequently be repaired easily
in the early stages of their development.

41. Energy Theory (能量理論） William Haddon (1970) proposed the idea
that many accidents and injuries involve the
transfer of energy.
The energy theory suggests that quantities
of energy, means of energy transfer and
rates of transfer are related to the kind and
severity of injuries.

42. Later, in 1972, Haddon proposed a matrix
(called Haddon’ matrix) to combine factors and
phases involved in the injury process.
Factors
Phases Human Vehicle Environment
Pre-event
Event
Post-event
Results

43. For example in a motor vehicle crash:
Safety 80
For example in a motor vehicle crash:
Phase Human Vehicle Environment
Pre-event sleepy, tired, good engine, snowy road,
alcohol lights on, down-hill, dark
intoxicated
Event not wearing air-bag tree, utility poles
seat belt, side-beam bridge abutments,
tissue
tolerance of
crash force
Post-event bleeding, damage EMT
fracture
Results injury, $ repairs, $ social costs

44. Using energy transfer as the accident-injury
model, Haddon suggests 10 strategies for
preventing or reducing losses.
Prevent the marshalling of energy.
(prevent the creation of the hazard in the
first place)
In this strategy the goal is not producing
energy or changing it to a form that cannot
cause an accident or injury.

45. Examples: not producing gun power, substituting
a safe substance for a dangerous one,
preventing the accumulation of snow where
avalanches are possible, not letting small
children climb to levels above the floor and
not letting a vehicle in motion.

46. 2. Reduce the amount of energy marshalled.
(reduce the amount of the hazard brought
into being)
Examples: keeping vehicle speeds down,
reducing the quantities or concentration of
high energy or toxic materials, limiting the
height to which objects are raised and
reducing machine speed to the minimum
needed when a machine is unguarded for
cleaning or maintenance.

47. 3. Prevent the release of energy. (prevent the
release of the hazard that already exists)
Examples: using various means or devices to
prevent elevators from falling, flammables
from igniting or foundations from being
undercut by erosion.

48. 4. Modify the rate at which energy is released
from its source or modify the spatial
distribution of the released energy.
Examples: reducing the slop of the road, limit
the weight of luggages in the airport

49. 5. Separate in space or time the energy being
released from the structure that can be
damaged or the human who can be injured.
Examples: separate paths for vehicular and
pedestrian traffic, placing electric power out
of reach, using traffic signals to phase
pedestrian and vehicular traffic.

50. 6. Separate the energy being released from a
structure or person that can suffer loss by
interposing a barrier.
Examples: Safety glasses, barrier guards,
radiation filters or shields, median barriers on
roadways, thermal insulation and explosive
barricades.

51. 7. Modify the surface of structures that come
into contact with people or other structures.
Examples: Rounded corners, blunt objects,
dull edges and larger surface areas for tool
handles.

52. 8. Strengthen the structure or person
susceptible to damage.
(Make what is to be protected more resistant
to damage from the hazard)
Examples: fire and earthquake-resistant
construction of buildings, training of
personnel and vaccination for diseases.

53. 9. Detect damage quickly and counter its
continuation or extension.
Examples: Sprinklers that detect heat and
spray water to prevent the spread of a fire.

54. 10. During the period following damage and
the return to normal conditions, take
measures to restore a stable condition.
Examples: rehabilitating an injured worker
and repairing a damaged vehicle.

55. Energy Release Theory According to this theory, an accident is caused
by a lack of engineering control. This lack of
control results in energy that is out of control
which puts causes stress limits to be violated,
whether on a person, machinery, or environment.
Therefore, accidents can be prevented by
instilling a proper engineering control to divert
the energy, which is the source of the hazards.

56. Single Factor Theory This theory is very limited in that it assumes
that every accident has only a single and simple
cause.
An application of this theory can be demonstrated
by reviewing what causes a forklift operator
puncturing a radioactive storage drum.

57. According to this theory, the cause of the
accident is the forklift.
Yet, by identifying this cause would not mitigate
or stop the problem. This theory fails to look at
other contributing factors such as workers’
training, storage method, or corrective actions.
This myopic focus makes this theory useless for
accident and loss prevention.

58. Multiple Factors Theory
The multiple factors theories use four M factors,
as shown below:

59. Multiple factors theories attempt to identify the
hazardous condition (pre-contact) that exist in an
operation by revealing the causes that will lead
to an accident.
Machine: tools, equipment, or vehicles that may
contribute to an accidents; usually
characterized by design, shape, size, specific
type of energy used to operate equipments

60. Media: environmental conditions surrounding
an accident, such as weather, walking surface;
usually characterized by gender, age, height,
weight, condition, memory, recall, knowledge
level
Man: people and human factors that could
contribute to an accident; usually
characterized by snow or water on a roadway,
temperature of a building,

61. Management: method used to select equipment,
train personnel, or ensure a relatively
hazard-free environment; usually
characterized by safety rules, organization
structure, policy and procedures

62. Multiple Factor Theories 2

63. Multiple Factor Theories 3

64. Multiple Factor Theories 4

65. Multiple Factor Theories 5

66. Multiple Factor Theories 6

68. Systems Theory of Causation
This theory states that the probability of an
accident lies with how the worker, machine, and
environment interact with each other.

69. For example the knowledge, skills, and ability,
whether acquired through training or gained
from years of experience, influences the way
a person deciphers the information regarding
the environment as well as how he will use the
machinery.
This, in effect, will affect his decision making
and therefore will have a bearing on the person
performing a job and therefore influence the
probability of a mishap.

70. 1. Goals Freedom Alertness Theory
Psychological/Behavioral Accident
Causation Theories
1. Goals Freedom Alertness Theory
According to this theory, accidents are the result
of low-quality worker behavior. Correction to
this behavior is in the form of raising worker
awareness through a positive organizational
culture and psychological climate.
For example, ensuring that workers are
disciplined to maintain good housekeeping
will reduce mishaps.

71. 2. Motivation Reward Satisfaction Model
This theory builds upon the previous theory.
According to this theory, rewards are the factor
that have the greatest effect upon performance.
If rewards are fairly disseminated as perceived
by the employees, there is an increased likelihood
of motivation which will produce positive safety
results.

72. For example, one of the DOE sites decided to
implement a program where a pool of safety
fund is allotted at the beginning of the year.
For every accident, a certain amount of
money is reduced from the original allocation.
Then at the end of the year, the remaining
funds, if any are divided up among the
employees. Since starting this program, the
number of mishaps have decreased
significantly.

73. Human Factors Theory This theory is based on the fact that human
errors cause accidents. The three human
factors which can lead to human errors are
overload, inappropriate activities, and
inappropriate response.

74. Overload can occur when a person must
perform excessive number of tasks. Despite
whether this person is qualified or not, it is the
overburden situation which creates the
scenario for a mishap.
An inappropriate activity can occur when a
person is not adequately trained to perform his
duties. This is one of the reasons for ensuring
that any trainee performing a “real” task
during an on-the-job training is supervised at
all times.

75. An inappropriate response occurs when a
qualified person purposely violates a procedure
for productivity or he fails to correct the
problem when it is detected.