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Human Reliability Analysis: A review of the state of the art

Human Reliability Analysis: A review of the state of the art

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an assessment <strong>of</strong> given control mode, as highlighted by figures<br />

provided in table below (Tab.1). As can be seen by contents <strong>of</strong><br />

table, each <strong>of</strong> specified control modes has an individual<br />

reliability level. In extended CREAM version, control modes<br />

play <strong>the</strong> role <strong>of</strong> a weighting factor which scales a nominal<br />

failure probability associated to a given cognitive function<br />

failure. This version <strong>of</strong> CREAM is intended to be used for<br />

purposes <strong>of</strong> a more in depth analysis <strong>of</strong> human interactions.<br />

TABLE I.<br />

Control mode<br />

RELIABILITY INTERVAL<br />

<strong>Reliability</strong> Interval<br />

strategic 0.5 E-5 < p < 1.0 E-2<br />

tactical 1.0 E-3 < p < 1.0 E-1<br />

opportunistic 1.0 E-2 < p < 0.5 E-0<br />

scrambled 1.0 E-1 < p < 1.0 E-0<br />

2.Context description. The intention <strong>of</strong> basic CREAM<br />

method is to use it as a screening technique with <strong>the</strong> aim <strong>of</strong><br />

identifying processes which require a deeper level <strong>of</strong> analysis;<br />

this analysis may <strong>the</strong>n be carried out by <strong>the</strong> extended CREAM<br />

method.<br />

3.Specification <strong>of</strong> Initiating Events. When using basic<br />

CREAM method, a task analysis is conducted prior to fur<strong>the</strong>r<br />

assessment. CPCs are assessed according to descriptors, given<br />

in <strong>the</strong> table below (Tab.2), in order to judge <strong>the</strong>ir expected<br />

effect on performance.<br />

TABLE 2.<br />

COMMON PERFORMANCE CONDITIONS (CPCS)<br />

CPC Descriptors Expected effect<br />

Adequacy <strong>of</strong> Very efficient Improved<br />

organisation<br />

Efficient Not significant<br />

Working<br />

conditions<br />

Adequacy <strong>of</strong><br />

MMI and<br />

operational<br />

support<br />

Availability<br />

<strong>of</strong><br />

procedures/<br />

Inefficient<br />

Deficient<br />

Advantageous<br />

Compatible<br />

Incompatible<br />

Supportive<br />

Adequate<br />

Tolerable<br />

Inappropriate<br />

Appropriate<br />

IRACST- International Journal <strong>of</strong> Research in Management & Technology (IJRMT), ISSN: 2249-9563<br />

Vol. 2, No. 1, 2012<br />

CPC Descriptors Expected effect<br />

plans<br />

Reduced<br />

Reduced<br />

Improved<br />

Not significant<br />

Reduced<br />

Improved<br />

Not significant<br />

Not significant<br />

Reduced<br />

Improved<br />

Number <strong>of</strong><br />

simultaneous<br />

goals<br />

Accettable<br />

Inappropriate<br />

Fewer than capacity<br />

Matching current<br />

capacity<br />

More than capacity<br />

Not significant<br />

Reduced<br />

Not significant<br />

Not significant<br />

Reduced<br />

Available Adequate<br />

Improved<br />

time<br />

Temporarily Not significant<br />

inadequate<br />

Continuously Reduced<br />

inadequate<br />

Time <strong>of</strong> day Day-time (adjusted) Not significant<br />

Adequacy <strong>of</strong><br />

training and<br />

expertise<br />

Crew<br />

collaboration<br />

quality<br />

Night-time<br />

(unadjusted)<br />

Adequate, high<br />

experience<br />

Adequate, limited<br />

experience<br />

Inadequate<br />

Very efficient<br />

Efficient<br />

Inefficient<br />

Deficient<br />

Reduced<br />

Improved<br />

Not significant<br />

Reduced<br />

Improved<br />

Not significant<br />

Not significant<br />

Reduced<br />

4.Error prediction. Assessments <strong>of</strong> <strong>the</strong> CPCs <strong>the</strong>n require to<br />

be adjusted according to some specified rules in order to take<br />

account <strong>of</strong> synergistic effects. Matrix above would be<br />

considered in <strong>the</strong> context <strong>of</strong> <strong>the</strong> situation under assessment and<br />

by this means <strong>the</strong> previously considered initiating events are<br />

<strong>review</strong>ed with respect to how <strong>the</strong>y could potentially lead to<br />

occurrence <strong>of</strong> an error. Rows <strong>of</strong> matrix identify <strong>the</strong> possible<br />

outcomes while <strong>the</strong> columns show <strong>the</strong> precursors. Analyst <strong>the</strong>n<br />

has task <strong>of</strong> identifying <strong>the</strong> columns for which all <strong>the</strong> rows have<br />

been similarly classified into <strong>the</strong> same group according to<br />

column headings. Predicting <strong>the</strong> possible outcomes for each <strong>of</strong><br />

rows should be done until <strong>the</strong>re are no remaining possible<br />

paths. Each <strong>of</strong> identified errors requires to be noted along with<br />

causes and <strong>the</strong> outcomes.<br />

5.Determination <strong>of</strong> control mode. Finally, a simple count is<br />

performed <strong>of</strong> <strong>the</strong> number <strong>of</strong> CPCs that are causing an<br />

improvement in reliability and those which are reducing it. On<br />

<strong>the</strong> basis <strong>of</strong> this number <strong>the</strong> probable control mode is<br />

determined.<br />

The main advantages <strong>of</strong> this methodology are: <strong>the</strong><br />

technique uses <strong>the</strong> same principles for retrospective and<br />

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