3. ACCIDENT AND INCIDENT INVESTIGATION
1
Learning objectives
At the end of this lesson, you should be able to:
Describe the causes of accidents
Explain the theories of accident causation
4. INTRODUCTION
This topic gives you an opportunity to
find out what went wrong. Learning
the lessons and taking action may
reduce, or even prevent, accidents in
the future.
5. ACCIDENT CAUSATION
THEORIES
Occupational accidents, work related
injuries and fatalities result from multiple
causes.
Many attempts have been made to
develop a prediction theory of accident
causation. Researchers in the field of OSH
have been trying for decades to
understand what causes accidents but so
far none has been universally accepted.
6. According to the domino theory;
88% of all accidents are caused by
unsafe acts of people
10% by unsafe actions
2% by "acts of God".
THE DOMINO THEORY
7. PREMISE OF THE THEORY
It proposed a "five-factor accident sequence" in which each factor would
actuate the next step in the manner of toppling dominoes lined up in a
row. The sequence of accident factors is as follows
8. Heinrich's Domino Theory states that accidents result
from a chain of sequential Events.
Metaphorically like a line of dominoes falling over.
When one of the dominoes falls, it triggers the next
one, and the next...
but removing a key factor (such as an unsafe condition
or an unsafe act) prevents the start of the chain
reaction.
This means that an accident is avoided, according to
Heinrich
9. The sequence is:-
• Injury, caused by an;
• Accident, due to an;
• Unsafe act and/or mechanical or physical hazard,
due to the;
• Fault of the Person, caused by their;
• Ancestry and Social Environment.
10.
11. Removal of one of the factors would prevent the
accident and resultant injury, with the key domino
to be removed from the sequence being number 3.
Although the author provided no data for his
theory, it nonetheless represents a useful point to
start discussion and a foundation for future
research.
12. Heinrich's Domino Theory states that accidents result
from a chain of sequential Events.
Metaphorically like a line of dominoes falling over.
When one of the dominoes falls, it triggers the next
one, and the next...
but removing a key factor (such as an unsafe condition
or an unsafe act) prevents the start of the chain
reaction.
This means that an accident is avoided, according to
Heinrich
13. Social Environment and Ancestry:
This first domino in the sequence deals with worker personality. Heinrich
explains that undesirable personality traits, such as
stubbornness,
greed, and
recklessness
can be "passed along through inheritance" or develop from a person's
social environment.
Theses contribute to Faults of Person.
14. Fault of Person:
The second domino also deals with worker personality traits.
Heinrich explains that inborn or obtained character flaws such as
bad temper,
inconsiderateness,
ignorance, and
recklessness
contribute to accident causation.
According to Heinrich, nature or environmental flaws in
the worker's family or life cause these secondary personal defects, which
are themselves contributors to Unsafe Acts, or and the existence of Unsafe
Conditions.
15. Unsafe Act and/or Unsafe Condition:
The third domino deals with Heinrich's direct cause of incidents.
Heinrich defines these factors as things like
"starting machinery without warning ...
and absence of rail guards.”
Heinrich felt that unsafe acts and unsafe conditions
were the central factor in preventing incidents,
and the easiest causation factor to remedy.
Heinrich defines four reasons why people commit unsafe acts
1. "improper attitude,
2. lack of knowledge or skill,
3. physical unsuitability,
4. [and] improper mechanical or physical environment."
16. He later goes on to subdivide these
categories into
"direct" and
"underlying" causes.
For example, he says, a worker who commits an unsafe act may do so
because he or she is not convinced that the appropriate preventative
measure is necessary, and because of inadequate supervision.
17. Accident:
Heinrich says,
"The occurrence of a preventable injury is the natural culmination
of a series of events or circumstances which invariably occur in a
fixed and logical order."
He defines accidents as, "events such as falls of persons, striking
of persons by flying objects are typical accidents that cause
injury."
18. Injury: Injury results from accidents, and some types of injuries Heinrich
specifies in his "Explanation of Factors" are cuts and broken bones.
To be fair to Heinrich, he does insist that
"the responsibility lies first of all with the employer." Heinrich specifies that a truly
safety-conscious manager will make sure his "foremen" and "workers" do as they
told, and
"exercise his prerogative and
obtain compliance ... follow through and see the unsafe conditions are
eliminated."
Heinrich's remedy for such non-compliance is strict supervision,
remedial training, and discipline.
19. Weakness of Domino Theory:
The domino theory has been noted as a one
dimensional sequence of events. Accidents are usually
multi-factoral and develop through relatively lengthy
sequences of changes and errors’. This has led to the
theory of multiple causation.
