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L8: Human Error (Latent Error and System Disasters (Error Precursors*…
L8: Human Error
Latent Error and System Disasters
Dynamics of Accident Causation
Latent variables + active acts + triggering effects
Trajectory of accident opportunity > shit happens
Counter Measures
Remove Errors
Identify error precursors > appropriate defences are in place
Significant consequences reduced almost to zero by:
Recognise and remove error precursors (if not possible, mitigate / lessen it)
ACTIVE ERROR VS. LATENT ERRORS**
Latent Error: Lay dormant for long periods of time > before realising
/ behaviour away from direct control interface
Summary: Latent errors is the
greatest threat
> safety of complex systems
Active Error: Effects felt immediately
/ frontline operators
Error Precursors*
Task Demands (pressures, challenges involved)
Work Environment (external environment)
Individual Capabilities (knowledge, skills)
Human Nature
Introduction
Unintended Behaviour (failure)
Lapses
(failure mental / memory storage)
Slips
(externalised / failure of execution)
Intended Behaviour (failure)
Mistakes
(error of planning)
Intentions, Actions and Consequences
Performance Levels and Error Types
Performance Levels
(SRK Model)
Rule-based Level (RB)
- signs / mistakes
Knowledge-based Level (KB)
- symbols / mistakes
Skill-based Level (SB)
- signals / slips & lapses
Key differences between SB, RB, KB*
Control mode
(where info is stored / processed / mental processes are done)
Predictability
(actions can be predicted > accessible to solve?)
Focus of attention
(when error occurs)
Ratio of error to opportunity for error
Type of activity
(routine actions / problem solving)
Influence of Situational Factors
(intrinsic / extrinsic)
Ease of Detection
(error)
Relationship to Change
(change in task pathway when error occurs)
Error Type
Lapses
Mistakes
Slips