Accident investigation, Health and Safety Course

1. ACCIDENTS
Causation, Reporting & Investigation

2. Causation Theories
Single Cause Domino Theory

Multiple Causation


3. Single Cause Domino Theory
Heinrich’s theory

Each factor is the fault of the factor that

immediately precedes it
A preventable injury is the natural culmination of

a series of events or circumstances, which occur
in a fixed logical order

4. Single Cause Domino Theory
Ancestry & Social Fault of Person Unsafe Act or Accident Injury
Environment Condition

5. Single Cause Domino Theory
If one of the dominoes is removed then the

chain of events will be halted, and the accident
will not happen
Element 3 (unsafe act and/or mechanical or

physical hazard) is probably the easiest factor
to remove

6. Single Cause Domino Theory
Bird & Loftus extended Heinrich’s theory to encompass the

influence of management in the cause & effect of accidents
They suggested a modified sequence as follows:

Lack of management control, permitting

Basic causes (personal & job factors), leading to

Immediate causes (substandard practices or conditions), which are the

direct cause of
The accident, which results in

Loss (negligible, minor, serious or catastrophic

This modified sequence can be applied to every accident and is

of basic importance to loss control management

7. Multiple Causation
May be more than one cause, not only in

sequence, but occurring at the same time
In accident investigation all causes must be

identified
Usually simple accidents have a single cause

Major disasters normally have multiple causes


8. Multiple Causation
Cause a
Cause b Unsafe Act
Cause c
Injury or
Accident
Damage
Cause d
Unsafe
Cause e
Condition
Cause f

9. Unsafe Acts
Categories:

Operating without clearance

Operating at unsafe speed

Rendering safety devices inoperative

Using unsafe equipment, or using it unsafely

Unsafe methods e.g. loading, carrying, mixing

Adopting unsafe position or posture

Working on moving or dangerous equipment

Horseplay e.g. distracting, teasing, startling

Failure to wear PPE

Lack of concentration; fatigue or ill health

Human Factors


10. Unsafe Acts
Unsafe acts can be active or passive:

 Active Unsafe Acts:
 Worker deliberately removes machine guard
 Passive Unsafe Acts:
 More difficult to deal with
 By pursuing an active safety policy, it is possible to achieve a
reduction in bad habits and hence accidents

11. Unsafe Conditions
Categories:

Inadequate guarding

Unguarded machinery

Defective, rough, sharp, slippery, decayed, cracked surfaces

Unsafely designed equipment

Poor housekeeping, congestion

Inadequate lighting, glare, reflections

Inadequate ventilation, contaminated air

Unsafe clothing or PPE

Unsafe processes

Hot, humid or noisy environment


12. Unsafe Acts/Conditions
The picture shows how unsafe acts & conditions may interact to produce an

accident. Accident potential is increased when unsafe acts & conditions occur
simultaneously. Of course, this is not to say that an act or condition alone
could not result in an accident.
Potential
Accident
Unsafe Acts Unsafe
Conditions

13. Accident Reporting
Information should be kept for all injuries, and

preferably for near misses
The safety practitioner needs to design a

suitable form to ensure that he gets the
information that he needs for investigations

14. Accident Investigation Records
Format:

Name & personal details of victim

Date, day and time of accident

Location of accident

Occupation of victim

Job being done at time

Nature of injury or damage

What inflicted the injury or damage

Who had control of the cause of the injury or damage

What actually happened

Basic and immediate causes

Immediate remedial action taken

Recommendations to prevent recurrence


15. Use of Investigation Records
Accident records are useless if they are used only to count accidents.

Detailed and thorough study of the records as part of the normal
ongoing accident prevention programme should yield the following
useful information:
Relative importance of the various injury & damage sources

Conditions, processes, machines and activities which cause the

injuries/damage
The extent of repetition of each type of injury or accident in each

operation
Accident repeaters, I.e. those workers who tend to be repeatedly injured

or are involved in more accidents
How to prevent similar accidents in future


16. Accident Investigation
Could be carried out by:

Safety Practitioner

Management or Supervisor

Safety Representative

Inspector

A joint investigation by company/safety rep is often a good idea

An investigation which does not discover what went wrong, and

produce some useful information and recommendations for
corrective action, is just a waste of time

17. Accident Investigation
Initial Actions

Questioning the victim

Treatment of victim is first priority

Immediate questioning may not be possible - they should be allowed to

collect their thoughts and control their nerves
Witnesses & Conditions

Investigator can usually go to accident scene and get a fairly complete

story from on-site conditions and witnesses
In all serious accidents and in all other cases where practicable,

conditions at accident scene should remain undisturbed until
investigation is complete

18. Investigators
Immediate supervisor:

 Likelyto know most about the situation
 Knows his own people better than anyone
 Has personal interest in determining causes, as
accidents affect the efficiency and morale of his
department
 Familiarity with staff could cause problems

19. Investigators
Recognising Hazards

Familiarity with plant, equipment and layout of operations will assist

in recognising hazards that have been overlooked for some time
Unsafe acts, as well as conditions, contribute towards most

accidents
It is not sufficient merely to recommend fitting a guard while

overlooking the unsafe act, such as rendering the guard ineffective
or placing hands in the danger zone
It is also insufficient to limit attention to an unsafe act if fitting a

better guard would reduce the likelihood of injury

20. Investigators
Safety Practitioner

 Necessary in more serious cases
 Supervisor may not have necessary authority
 Should seek assistance from local supervisor
 Investigator must have authority to go as far as is
necessary to get to the cause of the problem

21. The Investigation
Promptness

As soon as possible after the event

 Facts will be easier to determine and more details will be
remembered by those involved
Fire

Helpful if investigator is present during the fire

 Investigator may gain useful information by watching the
activities of firemen

22. The Investigation
Evidence

 Depending on severity of any injuries or damage,
investigator should be present during clear-up and
reinstatement as valuable clues may otherwise be
missed
 Failing which, supervisor should take it upon himself to
collect the necessary evidence

23. The Investigation
Equipment

Photographic equipment

Portable lights (electricity may be switched off or accident scene may be

poorly lit)
Sketchpad, pencils and measuring equipment

Record-keeping equipment e.g. notebook and cassette recorder

Sample collection equipment e.g. jars, paper bags, cartons etc.

Tools for cleaning debris or spillages should also be available

Portable gas/vapour detecting equipment


24. Accident Investigation Procedure
1. Inspection of the accident scene to collect any information
relating to physical conditions of the plant, equipment and
building
2. Interview witnesses and others likely to give information
concerning any unsafe acts or conditions which may have
contributed to the accident
3. Summarise all available evidence accurately in a written
report to management, recommending future actions to
prevent a recurrence

25. Inspection of the Scene
Careful, detailed look at accident scene, evaluating and noting

the following:
 Extent & severity of damage
 Damage to surrounding property
 Environmental conditions which may have had some bearing
on the accident, such as temperature, ventilation, humidity
and illumination
Survey the accident scene to see if there are any obvious

dangerous physical conditions which may have been
responsible for the accident

26. Inspection of the Scene
In the case of spillages, splashes or other escapes of

poisonous, explosive, flammable or other dangerous material, it
may be necessary to take samples for subsequent investigation
Where machinery or other equipment has been involved, it may

be necessary to issue instructions prohibiting the use or repair
of it until the investigation has been completed

27. Talking with On-Site Personnel
Easy to upset people when asking questions about what has

been done, or what has not been done
Casual remarks made during the site inspection may be quite

revealing and the investigator should continue to talk to any
personnel involved near the scene of the accident
This would also serve as an ideal opportunity to explain the

object of the exercise is to discover and root out the causes so
as to prevent a repetition. It is not to apportion blame or to
criticise any individual

28. Interviewing Witnesses
Types of Witness

Primary witness

The victim

Secondary witness

Extremely rare, the eyewitness

How many people really see the instant of an accident?

Tertiary witness

Can offer variety of corroborative statements regarding the acts of

people or environmental

29. Interviewing Witnesses
Putting witnesses at ease

Explain fully purpose of investigation

 Encourage participation and involvement
 Show interest in any ideas they might have about possible
preventive measures
 Witness must be assured that the purpose of the
investigation is not to blame anyone, but to attempt to find out
the cause and thereby reduce possibility of a recurrence

30. Interviewing Witnesses
Interview Location

Best to carry out interviews at scene of accident, as it

is easier for those involved to communicate effectively
with “props” close to hand
 Easier to explain what happened if witnesses are able
to point out specific things and recall their actions
related to specific locations

31. Interviewing Witnesses
Question Phrasing

Open ended question - what, where, when, how or who

 Questions starting with why may put witness on the defensive
 Typical questions:
What happened? What did you see?What time was it?

Where were you at the time? Where was the victim?

When did you realise something was wrong?

How did it happen? How were you involved?

How could it have been prevented?

Who else was involved? Who else saw it? Who reported it?


32. Interviewing Witnesses
Attitude

“What happened” will often promote the fullest response and it is vital the

investigator listens, without interruption, to the witness’s account of the
accident
If something is not understood, investigator should wait until witness has

completed his account before asking for clarification
Do not disagree with any of witness’s statement or make any judgements

on his evidence alone
What a witness believes to have happened will depend to some extent on

just how he perceived the situation, even though this might conflict with
the actual facts

33. Interviewing Witnesses
Conclusion

When witness’s account of accident has been heard,

investigator should repeat it to witness to ensure account is
fully understood
 Interview should be concluded on a positive note, which is
best achieved by discussing any ideas he may have
regarding prevention of a similar occurrence - this will serve
to reaffirm the purpose of the interview and ensure the
witness’s further co-operation, should it be needed

34. Interviewing the Victim
Ideally first to be interviewed

Injuries may be serious, or may be suffering

from shock
Should be interviewed at the earliest

opportunity
General principles for interviewing witnesses

apply

35. What Should be Investigated
ALL incidents/accidents should be investigated

Purpose is to find the cause, with the intention

of preventing a recurrence, rather than
apportioning blame
An injury usually involves some degree of blame

falling on management, supervision, victim or
workers