OHS Accident & Incident Investigation Lecture 1 Accident Theory.PDF

Accident Theories OUR JOURNEY TODAY Review the different theories regarding why workplace incident occur 1. Domino Theory 2. The three “E”s 3. Human Factors Theory 4. Safety Pyramid 5. Swiss Cheese Model  Anything that happens suddenly or What is an by chance without an apparent caus...

Accident Theories OUR JOURNEY TODAY Review the different theories regarding why workplace incident occur 1. Domino Theory 2. The three “E”s 3. Human Factors Theory 4. Safety Pyramid 5. Swiss Cheese Model  Anything that happens suddenly or What is an by chance without an apparent cause accident? An unforeseen and unplanned event or circumstance What is an Occurrence(s) arising out of or in the course of work that could or does incident? result in injury or ill health  An incident/accident with the limitation of What is an time removed - an “incident/accident” that is extended over a period of time occurrence? rather than a single observable happening What is a near An unplanned event that did not result in injury, illness, or damage - but had the miss? potential to do so What would you call this? What would you call this? What would you call this? Why do accidents, incidents, and near misses occur? Accident Theories The art and science that seeks to understand the deeper roots of why accidents happen. An accident (incident) is any unplanned, uncontrolled event that could result in personal injury or property damage Herbert William Heinrich Oct 6 1886-June 22 1962 Pioneer in the field of workplace health and safety According to Heinrich, an "accident" is one factor in a sequence that may lead to an injury. The factors can be visualized as a series of dominoes standing on edge; when one falls, the linkage required for a chain reaction is completed. Each of the factors is dependent on the preceding factor. Theory of Accident Causation aka Domino Theory of Accidents 1932 First Scientific Approach to Accident/Prevention - H.W. Heinrich Domino Theory – Causes of Adverse Effects Injury, caused by an Accident, due to an Unsafe act and/or mechanical or physical hazard, due to the Fault of the Person, caused by their Ancestry and Social Environment 88% 10% 2% of by unsafe acts of people by unsafe actions of industrial accidents are unavoidable Domino Theory Multiple Causation Theory Cause Unsafe Cause Act Near Miss Unsafe Unsafe Cause Act Accident Accident Cause Condition Injury Cause Unsafe Cause Condition Damage  Unsafe Acts What is the A violation of an accepted safe procedure difference between which could permit the occurrence of an accident an unsafe act and an Unsafe Conditions unsafe condition? A hazardous physical condition or circumstance which could directly permit the occurrence of an accident Unsafe Acts 80% of all injuries due to unsafe acts by people (Human Factors) Not being fit for work Using unsafe equipment or methods Adjusting moving machinery Improper lifting Horseplay Influence of drugs/alcohol Operating without authority Not wearing PPE Taking shortcuts or chances Unsafe Conditions 20% of all injuries due to unsafe working conditions (Latent Organization Weakness) Poor Layout – work flow, overcrowding and congestion Noise exposure Substandard housekeeping - waste bins, aisles, storage, signs/notices, wet floor Inadequate/inefficient machine guards Inadequate warning system Defective/damaged materials – hand tools, equipment, substances Illumination or ventilation – can’t see clearly or breathe properly Heinrich Pyramid Bird Accident Pyramid Safety Triangle Swiss Cheese Model Additional assumptions Accidents caused by unsafe acts Random behavior Solved by adding layers of defense Omits systemic factors i.e. how are holes created Active vs Latent Failures Organizational Latent Conditions Factors Budget cuts Excess workload Unsafe Latent Conditions Supervision Deficient training program Improper supervision Preconditions Latent Conditions for Poor training Unsafe Acts Mental Fatigue Unsafe Active Conditions Acts Failed to ensure surface could hold backhoe Failed or Absent Defenses Loss of situational awareness Accident & Injury  Redundancy: many layers of protection How can we Diversity: many different varieties of prevent this protection Independence: separate/autonomous from occurring? layers of protection Defenses in Depth Human Factors in Incidents Person Errors Violations Two Kinds of Error Active Errors errors that change equipment, system, or plant state triggering immediate undesired consequences. Latent Errors errors resulting in undetected organization-related weaknesses or equipment flaws that lie dormant. Human Error Human Errors 70% System Induced Error Occurrences 30% 90% Slip, trip or Human 10% lapse Error Equipment Failures 29 Error-Likely Situations are Predictable Task Demands Individual Capabilities Time pressure (in a hurry) Unfamiliarity w/ task / First time High Workload (memory requirements) Lack of knowledge (mental model) Simultaneous, multiple tasks New technique not used before Repetitive actions, monotonous Imprecise communication habits Irrecoverable acts Lack of proficiency / Inexperience Interpretation requirements Indistinct problem-solving skills Unclear goals, roles, & responsibilities “Hazardous” attitude for critical task Lack of or unclear standards Work Environment Illness / Fatigue Human Nature Work Environment Human Nature Distractions / Interruptions Stress (limits attention) Changes / Departures from routine Habit patterns Confusing displays or controls Assumptions (inaccurate mental picture) Workarounds Complacency / Overconfidence Hidden system response Mindset (“tuned” to see) Unexpected equipment conditions Inaccurate risk perception (Pollyanna) Lack of alternative indication Mental shortcuts (biases) Personality conflicts Limited short-term memory Unclassified 30 Conclusion A single theory may not suit all circumstances. Some theories address particular problems better than other theories. A combination of theories and models may be the optimal approach toward problem solutions. QUESTIONS?