SUMMARY OF SELECTED ACCIDENT MODELING PAPERS

ROSS APTED

TASK

To summarize a discuss the following journal articles and conference proceedings.

Papers compare accident modeling approaches in varying degrees of detail.

Understanding Accidents - From Root Causes to Performance Variability (Hollnagel, 2002)

Comparison of some selected methods for accident investigation (Sklet, 2003)

(Hollnagel, 2002)

UNDERSTANDING ACCIDENTS - FROM ROOT CAUSES TO PERFORMANCE VARIABILITY

BACKGROUND

Published in 2002 in the Proceedings of the 2002 IEEE 7th Conference on Human Factors and Power Plants.

Erik Hollnagel Department of Computer and Information Science, University of Linkoping, Sweden

Accidents Analysis and Accident Prevention

The variability of Human Performance

Modelling of Cognition

Developed FRAM and CREAM

AIM

To give an overview of the developments in accident modeling.

How these developments have effected accident analysis and prevention.

1. Summary and analysis of the general modeling approaches (Sequential, Epidemiological, Systemic).

2. The role of humans in the accident process(actions of humans, work mentally of humans).

Applies models to socio-

technical system sometimes.

STRUCTURE

Summary of modeling techniques

- Sequential

- Epidemiological

- Systemic

Comparison of approaches

Role of Humans in accidents

- actions of humans

- work mentality of humans

Conclusion

GENERAL MODELING APPROACHES -SEQUENTIAL

Ferry’s domino Model of accident causation (Ferry, 1988)

Accident Evolution and Barrier model (Svenson, 1991, 2001)

Analysis of sequential approach

DOMINO MODEL OF ACCIDENT CAUSATION

5 factors in the accident sequence

1. Social environment

Factors effect an individuals perception of risk

2. Fault of the person

Human error

3. Unsafe acts or environment

faulty equipment, hazards in the environment

4. Accident

5. Injury

(Ferry, 1988)

DOMINO MODEL OF ACCIDENT CAUSATION

Domino Diagram

Time

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Fau

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Uns

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Acc

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ACCIDENT EVOLUTION AND BARRIER MODEL

Accidents are represented as sequences of events or barriers that failed.

Target what went wrong.

Leaves out other factors that may be import in the investigation

(Øien, 2001)

SUMMARY OF SEQUENTIAL APPROACH

Attractive:

Allows you to think in a casual sequence

Represent as a graph

Allows easy communication of findings

Limited:

Not powerful enough to model more complex systems.

GENERAL MODELING APPROACHES -EPIDEMIOLOGICAL

Accident is described as a disease.

Some factor that effects the accident occur right away while others are latent.

Takes into account that events can manifest over time

Swiss cheese Model (Reason, 1997)

SUMMARY OF EPIDEMIOLOGICAL APPROACH

Overcome Limitations:

Superior to sequential models as latent events can be taken into account.

More suited to modeling complex systems.

Lack of detail:

Allowed the idefaction of general events that occurred could not go deeper.

SUMMARY OF SYSTEMIC APPROACH

Accidents naturally emerge, they are expected to occur. As detailed In Perrow’s Normal Accidents.(Perrow, 1984)

Focus:

Systemic models focus on the characteristics of a systems as oppose to a series of events that cause the accident in the system.

Difficult but powerful:

Ideal for complex systems but hard to represent graphically.

COMPARISON OF APPROACHES

(Hollnagel, 2002)

Table comparing general approaches

Highlights:1. What the accident

model produces

2. How the product information can be used in accident prevention

COMPARISON OF APPROACHES

Sequential models – search for root-cause of event - event linked by cause effect - cause is found then accident is prevented.

Epidemiological models – Looks at factors that may manifest later

- Looks at barriers that can be re-enforced or created to prevent further accident

Systemic models – looks for unusual relationships. - Monitors variability in systems performance

- Variability can be good and bad allows the system to develop, but bad variably must be trapped.

COMPARISON OF APPROACHES-CONCLUSION

.

These models should be used in conjunction with each other for the

best results.

No one modeling approach is better

than the other.

Each modeling approach has its own strengths

ROLE OF HUMANS IN ACCIDENTS

Humans play a role a ever level in an accident not just the sharp end.

Everyone blunt end is someone else's sharp end.

Blunt end sharp end relationship (Hollnagel, 2002)

ACTIONS OF HUMANS

Humans actions are not black and white and can only be judge in hindsight.

People do what they think is right at the time.

Different degrees of ‘being right’ not just correct or fail.

(Amalberti, 1996)

ACTIONS OF HUMANS

Being right or worn does nor accurately show humans roles in accidents.

ACTIONS OF HUMANS

In the sequential model an element is either correct or has failed, but human actions are not like this

Human actions are better suited to the epidemiological model as it allows for latent conditions , it takes into account that action may contribute to accident over time.

The systemic model is built on the concept of variability and does not focus on failures. This is perfect for representing variability of human action.

WORK MENTALITY OF HUMANS

Efficiency-Thoroughness Trade-off (ETTO) Principle

Human performance must satisfy conflicting criteria.

Will try and meet task demand and be as thorough as believed necessary while still being as efficient as possible and not wasting effort.

Performance can only increase in a stable environment

RO-RO ferries

Normal performance

(Hollnagel, 2002)

CONCLUSION

“Normal performance and failures are emergent phenomena”

Neither can be attributed to a specific part of function of the system.

The adaptability of human work is the reason behind its efficacy and it failures.

(Hollnagel, 2002)

(Sklet, 2004)

COMPARISON OF SOME SELECTED METHODS FOR ACCIDENT INVESTIGATION

BACKGROUND

Published in 2003 in Journal of Hazardous Materials

Snorre SkletDepartment of Production and Quality Engineering Norwegian University of Science

and Technology, Norway

Risk Analysis and Risk Influence Modeling

Safety Barriers

Safety Management

Accident Investigation

Does a lot of work with the oil industry

AIM

To give a brief summary of highly recognized accident investigation methods developed over last decade .

To compare these selected methods to highlight there qualities and deficiencies.

1. Summary of the methods ) brief summary of each one, framework for comparison).

2. Comparison of methods(table, analysis of comparison).

STRUCTURE

Selected Methods

Framework of comparison

Results of comparison

Analysis of comparison

Conclusion

SELECTED METHODSEvents and causal factors charting and analysis.

Barrier analysis.

Change analysis.

Root cause analysis.

Fault tree analysis.

Influence diagram.

Event tree analysis.

Management and Oversight Risk Tree (MORT).

Systematic Cause Analysis Technique (SCAT).

Sequential Timed Events Plotting (STEP).

Man, Technology and Organisation (MTO)-analysis.

The Accident Evolution and Barrier Function (AEB) method.

TRIPOD.

Acci-Map.

methods are commonly used and widely acknowledge in academic and accident investigating community

No systemic methods compered

FRAMEWORK OF COMPARISON

Details Framework of comparison highlighting the strengths and weakness of each technique.

7 categories

Whether the methods give a graphical description of the event sequence or not?

Can give overview of events

Allows for clear communication

Easy to see broken link

To what degree the methods focus on safety barriers?

Analysis of protective elements in the the system

FRAMEWORK OF COMPARISON

The level of scope of the analysis.

Which levels of Rasmussen’s classification of sociotechnical systems (Rasmussen, 1997) does the method model.

(Rasmussen, 1997)

FRAMEWORK OF COMPARISON

What kind of accident models that has influenced the methods?

sequential model, epidemiological model, systemic model

Whether the different methods are inductive, deductive, morphological or non-system-oriented?

The way in which the method looks at the accident e.g. does reason from the general to the specific.

FRAMEWORK OF COMPARISON

Whether the different methods are primary or secondary methods?

Primary Method – Self contained, stand alone method.

Secondary Method – used in conjunction with other method to provide special input.

The need for education and training in order to use the methods.

Novice – no experience or training is needed.

Specialist – In between Novice and expert.

Expert – Formal education and training is needed.

RESULTS OF COMPARISON

(Sklet, 2004)

ANALYSIS OF THE COMPARISON

The strongest in terms of graphical representation is STEP as it does not use a single axis and can represent one – one or one - *

Scope of most methods focus on levels 1-4 of the sociotechnical systems

Identifying the casual factors or event paths is important.

CONCLUSION

Accidents do not have a single cause so the investigation should reflected this buy using multiple methods.

A graphical representation is key, as it allows easy communication of information.

There should be one person of every investigation team that has the knowledge of different accident modeling techniques so the right tools can be chosen for the job

REFERENCESAmalberti, R. (1996). La conduite des systkmes ri risques. Paris: PUF.

Department of Energy. (1999). DOE Workbook, Conducting Accident Investigations . Washington,: Department of Energy.

Ferry, T. (1988). Modern Accident Investigation and Analysis. Second Edition. New York: Wiley.

Høyland, A., & Rausand, M. (1994). System reliability Theory: Models and Statistical Methods. New York: Wiley.

Hollnagel, E. (2002). Understanding accidents-from root causes to performance variability. Human Factors and Power Plants, 2002. Proceedings of the 2002 IEEE 7th Conference on , (pp. 1 - 1-6 ).

Lehto, M. (1991). Models of accident causation and their application: Review and reappraisal. journal of engineering and technology management , 173.

Perrow, C. (1984). Normal Accidents: Living With High-Risk Technologies. New york: Basic books.

Rasmussen, J. (1997). Risk management in a dynamic society: a modelling problem. Safety Sci. , 183–213.

Reason, J. (1997). Managing the Risks of Organizational Accidents. Aldershot: Ashgate.

Sklet, S. (2003). Comparison of some selected methods for accident investigation. Journal of hazardous materials , 29-37.

Svenson, O. (2001). Accident and Incident Analysis Based on the Accident Evolution and Barrier Function ( AEB) Model. Cognition, Technology & Work , 42-52.

Svenson, O. (1991). The Accident Evolution and Barrier Function (AEB) Model Applied to Incident Analysis in the Processing Industries. Risk Analysis , 499–507.

Øien, K. (2001). Risk indicators as a tool for risk control. Reliability Engineering & System Safety , 129–145.