TASKTo summarize a discuss the following journal articles andconference proceedings. Papers compare accident modeling approaches in varying degrees of detail.Understanding Accidents - From Root Causes toPerformance Variability(Hollnagel, 2002)Comparison of some selected methods for accidentinvestigation(Sklet, 2003)
UNDERSTANDING ACCIDENTS - FROM ROOTCAUSES TO PERFORMANCE VARIABILITY(Hollnagel, 2002)
BACKGROUNDPublished in 2002 in the Proceedings of the 2002 IEEE 7thConference on Human Factors and Power Plants. Erik Hollnagel Department of Computer and Information Science, University of Linkoping, SwedenAccidents Analysis and Accident PreventionThe variability of Human PerformanceModelling of CognitionDeveloped FRAM and CREAM
AIMTo give an overview of the developments in accidentmodeling. 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).
STRUCTURESummary of modeling techniques - Sequential - Epidemiological - SystemicComparison of approachesRole of Humans in accidents - actions of humans - work mentality of humansConclusion
GENERAL MODELINGAPPROACHES -SEQUENTIALFerry’s domino Model of accident causation (Ferry, 1988) Accident Evolution and Barrier model (Svenson, 1991, 2001)Analysis of sequential approach
DOMINO MODEL OFACCIDENT CAUSATION(Ferry, 1988)5 factors in the accident sequence1. Social environment Factors effect an individuals perception of risk2. Fault of the person Human error3. Unsafe acts or environment faulty equipment, hazards in the environment4. Accident5. Injury
DOMINO MODEL OFACCIDENT CAUSATIONDomino Diagram Time
ACCIDENT EVOLUTIONAND BARRIER MODELAccidents are represented as sequences of events orbarriers that failed. Target what went wrong.Leaves out other factors that may be import in theinvestigation (Øien, 2001)
SUMMARY OFSEQUENTIAL APPROACHAttractive:Allows you to think in a casual sequenceRepresent as a graph Allows easy communication of findingsLimited:Not powerful enough to model more complex systems.
GENERAL MODELINGAPPROACHES -EPIDEMIOLOGICALAccident 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 timeSwiss cheese Model (Reason, 1997)
SUMMARY OFEPIDEMIOLOGICALAPPROACHOvercome Limitations:Superior to sequential models as latent events can be takeninto account.More suited to modeling complex systems.Lack of detail:Allowed the idefaction of general events that occurred couldnot go deeper.
SUMMARY OFSYSTEMIC APPROACHAccidents naturally emerge, they are expected to occur. Asdetailed In Perrow’s Normal Accidents.(Perrow, 1984)Focus:Systemic models focus on the characteristics of a systemsas oppose to a series of events that cause the accident in thesystem.Difficult but powerful:Ideal for complex systems but hard to represent graphically.
COMPARISON OFAPPROACHES Table comparing general approaches Highlights: 1. What the accident model produces 1. How the product information can be used in accident prevention(Hollnagel, 2002)
COMPARISON OFAPPROACHESSequential 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 furtheraccidentSystemic 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 OFAPPROACHES-CONCLUSION No one modeling approach is better. than the other. Each modeling approach has its own strengths These models should be used in conjunction with each other for the best results.
ROLE OF HUMANS INACCIDENTSHumans play a role a ever level in an accident not just thesharp end.Everyone blunt end is someone elses sharp end. Blunt end sharp end relationship (Hollnagel, 2002)
ACTIONS OF HUMANSHumans actions are not blackand white and can only be judgein 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 HUMANSBeing right or worn does nor accurately show humans rolesin accidents.
ACTIONS OF HUMANSIn the sequential model an element is either correct or hasfailed, but human actions are not like thisHuman actions are better suited to the epidemiological modelas it allows for latent conditions , it takes into account that actionmay contribute to accident over time.The systemic model is built on the concept of variability anddoes not focus on failures. This is perfect for representingvariability of human action.
WORK MENTALITY OFHUMANSEfficiency-Thoroughness Trade-off (ETTO) Principle(Hollnagel, 2002)Human performance must satisfy conflicting criteria. Will try and meet task demand and be as thorough as believed necessary while still being as efficient aspossible and not wasting effort.Performance can only increase in a stable environmentRO-RO ferries Normal performance
CONCLUSION“Normal performance and failures are emergent phenomena”(Hollnagel, 2002) Neither can be attributed to a specific part of function of the system.The adaptability of human work is the reason behind itsefficacy and it failures.
COMPARISON OF SOME SELECTED METHODSFOR ACCIDENT INVESTIGATION(Sklet, 2004)
BACKGROUNDPublished in 2003 in Journal of Hazardous Materials Snorre SkletDepartment of Production and Quality Engineering Norwegian University of Science and Technology, NorwayRisk Analysis and Risk Influence ModelingSafety BarriersSafety ManagementAccident InvestigationDoes a lot of work with the oil industry
AIMTo give a brief summary of highly recognized accidentinvestigation 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).
STRUCTURESelected MethodsFramework of comparisonResults of comparisonAnalysis of comparisonConclusion
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. No systemic methods compered
FRAMEWORK OFCOMPARISONDetails Framework of comparison highlighting the strengthsand weakness of each technique.7 categoriesWhether the methods give a graphical description of the event sequenceor not? Can give overview of events Allows for clear communication Easy to see broken linkTo what degree the methods focus on safety barriers? Analysis of protective elements in the the system
FRAMEWORK OFCOMPARISONThe level of scope of the analysis. Which levels of Rasmussen’s classification of sociotechnical systems (Rasmussen, 1997) does the method model. (Rasmussen, 1997)
FRAMEWORK OFCOMPARISONWhat kind of accident models that has influenced the methods? sequential model, epidemiological model, systemic modelWhether 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 OFCOMPARISONWhether the different methods are primary or secondarymethods? 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 THECOMPARISONThe strongest in terms of graphical representation is STEPas it does not use a single axis and can represent one – oneor one - *Scope of most methods focus on levels 1-4 of thesociotechnical systemsIdentifying the casual factors or event paths is important.
CONCLUSIONAccidents do not have a single cause so the investigationshould reflected this buy using multiple methods.A graphical representation is key, as it allows easycommunication of information.There should be one person of every investigation team thathas the knowledge of different accident modeling techniquesso the right tools can be chosen for the job
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