e5.1 - Theories/models and use of loss causation techniques Flashcards
Incident
An unplanned event which has the potential to cause loss of some kind
Accident
An unplanned, unwanted event which causes loss of some kind
Heinrich (1931)
Tip of triangle - major accident
Middle of triangle - minor accident
Base of triangle - non-injury accident
Accident ratio studies demonstrate…
Most incidents do not result in a high severity outcome
Matter if chance whether an event results in injury, damage or near miss
All accidents and incidents should be investigated to find cause
Resources should be based on potential loss rather than actual loss
Near Misses (Accident ratio studies)
Near misses often have an identical root cause to serious incidents and can reveal management system failures before serious incidents occur
Not every near miss or minor accident could lead to a serious one.
Limitations of accident ratio studies
Different triangles from different organisations cannot be easily compared
Certain amount of data needed before comparisons
Similar injuries, different causes
Many injuries are musculoskeletal which could not have ended up as fatalities
Measures failure rather than success
Domino Theory
Single cause theory
Accident occurs due to five sequential factors
Each factor is caused by the preceding one
Remove any of the first three factors, prevent the accident
Domino theory - 5 factors
LACK OF CONTROL (inadequate system, standards)
INDIRECT CAUSE (personal factor & job system factor)
IMMEDIATE CAUSES (substandard act, practice or conviction)
ACCIDENT EVENT (event or contact)
INJURY/DAMAGE (the result)
Domino theory limitations
Simplistic
Reactive not proactive
Not useful in prediction the likelihood of accidents
Encourages focus on immediate rather than underlying causes
Restricts the search for multiple causes
Multi Causality theory
More than one cause of the accident, not just in sequence but occurring simultaneously e.g. Fuel+oxygen+source of ignition = Fire
Each must come in the right quantities at the right time
Multi causality theory - Advantages
Helps to consider many possible organisational and cultural issues
Encourages search for underlying/root causes
Underlying root causes encourage wider look at org. arrangements
Multi causality theory - limitations
More complex, high competence needed
Time consuming
Over complicating when causes are simple to understand
Immediate causes
Unsafe act/omission (people) or unsafe condition (place, equipment, materials)
Underlying causes
Management failing that allows the immediate causes to occur (e.g. failure to carry out risk assessment)
Root cause
Deeper management failings from which all underlying causes stem (e.g. lack of resources)
Swiss cheese model (James Reason)
Risk management in 4 layers
A failure in one layer (poor control) can be picked up by the next layer which has no holes (i.e. the control works)
Swiss cheese model - latent failures
Contributory factors in the ‘system’
May have laid dormant for a long time
Introduced by organisational or managerial factors
Accumulate over time
Lack of management control
Lie dormant until triggered by ‘active’ failure
Swiss cheese model - Active failure
Due to human error (accidental) or violation (deliberate)
Fault tree analysis
A graphical technique used in risk assessment to provide combinations of possible occurrences that can result in an undesired result.
Used in multi causal investigation following back to its root cause using a logic diagram
Determine root causes by beginning with unwanted event (incident/accident)
Event tree analysis
Based on binary logic (component either succeeds or fails)to assess protective systems designed to prevent
Analyses the possible consequences from failures
Event trees start with an INITIATING event and work towards the TOP event, the opposite to fault tree analysis.
Event tree analysis - Limitations
Accuracy of data to determine probability of an event and the high degree of competence and expertise needed to complete them
Bowtie Model
Method for visualizing hazards, barriers and control measures
Analysis of hazard and consequence to incidents (Known as TOP event)
LEFT SIDE of bowtie
Comprises a fault tree
Barriers in place should be sufficient to stop event
RIGHT SIDE of bowtie
Comprises event tree
Mitigation barriers to minimise consequences of incident
