Chapter 14: Safety, accidents, and human error

1. Chapter 14: Safety, accidents, and human error • Factors contributing to accidents and human error • Descriptions and models of human error • Accident and incident investigation • Hazard management (eliminate, reduce, control, mitigate) • Safety analysis and product design • Warning design, decision making, and risk taking

2. Safety legislation and product liability • Moral and economic concerns of occupational safety • Failure to perform safely when used in • a reasonably foreseeable manner • or if the inherent risks outweighed the benefits • Juggling chainsaws, using a lawnmower as a hedge trimmer, removing guards

3. Organizational Factors Active versus Latent Failures (Reason, 1990) • Latent Conditions • Excessive cost cutting • Inadequate promotion policies • Latent Conditions • Deficient training program • Improper crew pairing Unsafe Supervision • Latent Conditions • Poor CRM • Mental Fatigue Preconditions for Unsafe Acts Unsafe Acts • Active Conditions • Failed to Scan Instruments • Penetrated IMC when VMC only Failed or Absent Defenses “Robbing the pillar” • Accident & Injury • Crashed into side of • mountain

4. Descriptions and models of of human error • No such thing as human error?? • Human error as starting point of investigation • Genotype and phenotype • Phenotype: external appearance of error • Genotype: underlying cognitive mechanisms • Errors of omission/commission • Slips and mistakes (SRK levels of cognitive control)

5. Descriptions and models of of human error • Human reliability assessment • Identify potential errors • Quantify error likelihood • Combine to assess system-level effects: THERP, GEMS, SHERPA • No one method is the “best” • All depend on analyst skill • Eliminate through: selection, training and design • Design to be error proof and error tolerant

6. Accident and incident investigation • Incidents= Near misses or near accidents • Why incidents rather than accidents? • How to code errors? • How to respond to errors? • Hazard analysis as proactive accident/incident investigation

7. Factors contributing to errors and accidents Work System Employee Job Equipment and tools Physical environment Social environment Management or Design Error Accident/ Injury Hazard Operator error

8. Hazards • Set of conditions that, together with other conditions, will inevitably lead to an accident • Electrical • Mechanical • Pressure • Toxic substances • Radiation (300 REM kills 50% in 50 days) • Fire • Fall and trip (11ft fall kills 50%, but flight attendant survived 33,000 ft fall)

9. Managing hazards • Hazard elimination • Substitution (lambs rather than lions) • Decoupling • Elimination of specific human errors • Hazard reduction • Design for control • Lockouts • Hazard control • Reduce exposure • Isolation and containment • Damage minimization

10. Hazard management • Focus on severe hazards • Criticality = Severity X Frequency • Reduce hazards by addressing: • Source (elimination, control, limit damage) • Path (guards, task redesign) • Person (warnings, training) • Administration (rules, regulations)

11. Hazard management: Addressing the source • Hazard elimination • Substitution (lambs rather than lions) • Decoupling (separate grain production from consumption) • Hazard control • Reduce exposure (minimize additive effects) • Isolation and containment • Damage minimization • First aid stations • Emergency response plan • Safety programs for a systems approach

12. Safety analysis and product design • Bottom-up (Failure modes and effects analysis) • Top-down (Fault tree analysis) • Analyze: • Task • Users • Environment • Identify and evaluate hazard controls • Effect on usefulness and safety of product • Effect on cost • Comparison to other products

13. Warning design, decision making, and risk taking • Risk perception depends on perceived • Criticality (more influential than frequency) • Frequency/likelihood • Availability • Response depends on perceived risk and cost of compliance

14. Warning design • Warnings should contain: • Signal word (Danger, Caution, Warning) • Description of hazard • Consequences • Behavior needed to avoid hazard • Challenges to warning design • Perceive warning • Comprehend severity, Language/cultural barriers • Proliferation can reduce salience and compliance

15. Key concepts regarding safety, accidents, and error • Human error is the starting place for investigation • Types of error and the need to go beyond the surface description of single causes • Hazard management: address severe hazards at their source • Perceived risk and cost of compliance govern risky behavior