SOCIO-TECHNICALSYSTEMSSocio-technical system – The interactions between people and their behavior with technology while occupying societys complexinfrastructures.Examples:Power plants, national healthcare system, spacemissions, stock market , aviation systems. What happens when they go wrong
THE NEED TO MODELACCIDENTSAccidents in these types of organizations are: have a highcost, decrease efficacy and can lead to serous harm or deathof humans.If the source of the accident is identified the potentialaccidents can be eliminated.To obtain this information must effectively represent thesystem in which the accident occurred and the accidentitself. Accident Models.
ACADEMICLITERATURE IUnderstanding Accidents - From Root Causes toPerformance Variability(Hollnagel, 2002)Key points:Discusses the generalmodeling approaches andidentifies each whatapproach shows orhighlights. Main types of Accident model. (Hollnagel, 2002)
ACADEMICLITERATURE IThe suitability of these approaches focusing on the humanaspects of Sociotechnical systems.Humans 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)
ACADEMICLITERATURE IIn 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.
ACADEMICLITERATURE IIComparison of some selected methods foraccident investigation(Sklet, 2004)Key points:Compares a selection ofaccident investigationmethods, theses methodsare commonly used andwidely acknowledge inacademic and accidentinvestigating community. Methods compared in article
ACADEMICLITERATURE IIDetails 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
ACADEMICLITERATURE IIThe level of scope of the analysis. Which levels of Rasmussen’s classification of sociotechnical systems (Rasmussen, 1997) does the method model. (Rasmussen, 1997)
ACADEMICLITERATURE IIWhat kind of accident models that has influenced the methods? sequential model, epidemiological model, systemic modelWhether the different methods areinductive, 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.
ACADEMICLITERATURE IIWhether 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.
ACADEMIC LITERATURE II Each method is briefly detailed, the comparison is analyzed and discussed. Characteristics of different methods.(Sklet, 2004) Conclusion: no one accident investigation technique is perfect and that to be most effective they must be used in conjunction.
ACADEMICLITERATURE IIIModels of accident causation and their application: Reviewand reappraisal(Lehto, 1991)Key pointsCategorizes and compares 54 different accident causingmodels. A fairly comprehensive at the time of publication list categorized and cited.Conclusion: modeling methods are to narrow and a better model is need to take into account human and technological interaction.
SEQUENTIAL ACCIDENT MODELS
SEQUENTIALACCIDENT MODELSSimplest form of accident modeling.Describes the accident as a series of events that occur in aparticular order.Events occur along a linear timeline.Analysis: Identifies specific cause and broken links in accident chain. Goal is to eliminate broken links.
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
FAULT TREEANALYSIS(Høyland & Rausand, 1994)Graphical representation of normal events, systemfailures, human errors and environmental factors.Logic gate are used to construct chains of events.Used to identify sequences off failure.Advantages:Root cause can be easily be identified.Human readable easy to communicate events that lead toaccident.
FAULT TREEANALYSIS Simple fault tree for a fire breakout
EVENTS AND CAUSALFACTORS CHARTING (Department of Energy, 1999)Diagram used to show the events of the accident inchronological order.Primary events – the main sequence of events that lead to the accident are drawn in a horizontal line.Secondary events – Placed above or below each primary event that it directly relates to.Conditions influencing the events – Passive and describe states, place above relevant events.
EVENTS AND CAUSALFACTORS CHARTING (Department of Energy, 1999)
SEQUENTIAL ACCIDENTMODELS SUMMARYAdvantages:Human readable, easy to communicate chain of events.Can identify root cause or break in chain of events that leadto accident.Good starting of point.Disadvantages:Does not take into account latent factors.Inadequate to model the variability of Sociotechnicalsystems.
SEQUENTIAL ACCIDENTMODELS SUMMARYMore modeling techniques:• Event tree analysis.• Management and Oversight Risk Tree (MORT).• Sequential Timed Events Plotting (STEP).• Man, Technology and Organization (MTO)-analysis.• TRIPODLinks last accessed 29/06/12
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 StatisticalMethods. New York: Wiley.Hollnagel, E. (2002). Understanding accidents-from root causes to performancevariability. Human Factors and Power Plants, 2002. Proceedings of the 2002 IEEE 7thConference on , (pp. 1 - 1-6 ).Lehto, M. (1991). Models of accident causation and their application: Review andreappraisal. journal of engineering and technology management , 173.Rasmussen, J. (1997). Risk management in a dynamic society: a modelling problem.Safety Sci. , 183–213.Sklet, S. (2004). Comparison of some selected methods for accident investigation.Journal of hazardous materials , 29-37.