2. IN THIS LECTURE
This lecture will focus on how accidents and serious incidents are
investigated and analysed
• When do investigations happen?
• How are they conducted?
• What analytical methods are used?
3. INVESTIGATIONS
Accidents and failures need to be investigated.
• Investigations enable you to identify the (most likely) causes of
accidents and failures
• The causes and conditions leading up to accidents and
incidents are often complex, and immediate reactions may
be wrong
• Investigations seek to uncover underlying causes, not just
the immediate causes
• Investigations should also address how future accidents can
be avoided
• In this context, investigations are primarily to prevent future
occurrences than establish responsibility
4. INVESTIGATIONS
The basic steps of an investigation are
1. Collection phase: Evidence, and facts are sought
2. Analysis phase: The evidence and facts are analysed and
opinions invited from experts and other parties
3. Judgements phase: Judgements are made about the
causes of an incident or accident and the associated
responsibilities
4. Follow up: Recommendations should be made on how to
stop similar problems happening again.
In practice, the process will be iterative.
5. INVESTIGATIONS
There are limitations on the investigation process. Investigations
can be costly.
• We may never know all the facts. With complex systems, it
can be very hard or impossible to know everything that
happened in the run up to an incident. In major accidents
sources of evidence may be damaged or lost.
• There will always be subjective views and
uncertainties, especially around human actions.
Judgements need to be made about the extent to which an
incident can be investigated.
Investigations often conclude with the “likely” or “probable” causes
rather than a definitive version of events
6. WHO INVESTIGATES?
The scope and emphasis of an investigation is likely to reflect the
position of the investigator
An investigator ought to be independent.
• In practice, this can be hard to achieve.
• Some industries have an official, independent investigation
organisation
• In the event of a major incident, a „public enquiry‟ may be
used, in which the evidence and investigative process is
made public and so open to scrutiny.
7.
8. ANALYSIS
The analysis phase of an investigation needs to explore and
evaluate often complex information.
Experts and specialists may need to be involved at this point.
There is no standard method for analysing an accident, and
continuing debate about how this is best done.
Approaches include
• Narrative approaches
• Causal chains
• Systems approaches
9. NARRATIVE APPROACHES
All accident investigations will produce a narrative of some kind.
Many reports are purely a narrative and a set of conclusions. A
narrative is a written account of an incident or accident.
• Producing this can be non-trivial because it can be difficult to
structure events, many of which may have occurred
simultaneously and many of which may have ambiguities, into
a linear document.
Producing a narrative is a key step in making sense of an incident
Narrative accounts have serious limitations however. It is difficult
to evaluate their depth and coverage, and they tend to „storify‟
complex events.
10. “ROOT CAUSE” APPROACHES
Many approaches have been developed to systematically identify
the root causes of an incident. These approaches are based on
the idea that the immediate events in an incident are symptoms of
a much deeper problem.
Root cause analysis techniques usually express events as a
chain. The chains often branch, and multiple chains can be
synchronised to represent parallel events.
• Examples: MORT (management oversight risk tree), FMEA
(Failure mode and effects analysis) , Barrier analysis, WBA
(Why-because Analysis)
11. “ROOT CAUSE” APPROACHES -
LIMITATIONS
The stopping problem
• A causal chain could in theory go backwards indefinitely.
The proximity problem
• A root cause is often found to be something proximal to
the accident (often a human operator).
The causation problem
• Hindsight and investigative biases frame particular
actions in terms of their contributions to an outcome
However, this does not mean that it is wrong to try to
identify underlying causes
Investigations usually refer to the “likely” or “probable” root
causes
12. SYSTEMS METHODS
Systems methods for accident analysis have come into use over
the last decade.
• From this perspective, accidents result from inadequate
control or enforcement of safety-related constraints on the
development, design, and operation of the systems.
Systems methods emphasise controls over the system itself. This
recognises that no system is inherently safe, and that systems
(particularly socio-technical systems) adapt and change over time.
• A key approach is STAMP (Systems-Theoretic Accident
Model and Processes).
13. SYSTEMS METHODS
Key criticisms of systems models
• They are often used as a means of pursuing and attributing
blame to high level people in an organisation
• They can turn attention too far away from the actual design
and implementation of the technology
14. HINDSIGHT AND
FORESIGHT
It is essential to learn from our mistakes, but we should not wait
for accidents to happen before we try to improve the dependability
of systems. How can we predict problems that may occur? How
can we ensure systems are resilient to possible problems.
Several of the methods mentioned in this lecture can be used to
follow through the consequences of possible problems or failures.
Predicting possible causes and consequences of failure, unless in
very narrow circumstances, can involve many arbitrary decisions.
16. INVESTIGATION
The Columbia Accident Investigation Board was an independent
board set up to analyse the Columbia disaster
• 13 board members and many investigators
• Investigation took around 5 months
• Cost approximately 17 million dollars
• 230 page report produced
The proximal cause was fairly clear from the outset. The
investigation sought to focus on underlying causes.
• The investigation focused on
organisational, historical, budgetary and political factors in the
shuttle programme
• The questions surrounded the issue that foam strikes were
routinely ignored
17. KEY POINTS
Investigations are important for learning from failures.
Investigations often show that initial assumptions about the cause
of an incident are wrong or partial. They aim to find underlying or
“root” causes.
All investigations involve some sort of judgement. Investigations
should be as neutral as possible, but in practice this is difficult to
achieve.
There are many methods for analysing an incident or
accident, and no single right way to do this.
18. FURTHER READING
MAIB – Maritme Accident Investigation Branch
• http://www.maib.gov.uk/home/index.cfm
AAIB – Air Accidents Investigation Branch
• http://www.aaib.gov.uk/home/index.cfm
Columbia Accident Investigation Branch
• http://caib.nasa.gov/
