Notes on Accident Causation and Incident Investigation
Accident Causation: Beyond Surface-Level Explanations
Initial Perspectives on Accident Causes:
Early discussions brought up "human factors" and "unsafe conditions" as general accident causes.
The instructor stressed the importance of specificity and detail when identifying causes, urging students to "skew over detail now" rather than broad generalizations.
Human Error: Definition, Implications, and Nuance
Defining Human Error:
Initially, students define error as simply "wrong" or a "mistake."
"Human error" is presented as a complex concept, extending beyond simple individual fault.
The Discrepancy Between Training and Practice (OJT vs. Reality):
Many employees, after initial training or orientation (OJT), are told the proper way to perform tasks.
However, experienced colleagues often introduce alternative, non-standard methods, stating, "I know they tell you this is how we're supposed to do it, but this is the way we're actually asked to do it."
Consequences: This deviation can lead to problems because established processes usually have a specific rationale for safety and efficiency.
Common Justification: The excuse, "I've been doing it this way for 35 years," is often used to justify these non-standard practices.
Historical Study on Human Error in Maintenance:
A study was conducted involving 75,000 maintenance workers to understand accident causation.
The instructor poses the question of whether the finding that most incidents are a direct result of human error still holds true today.
General Consensus: While not always the sole cause, human error can be related to almost any incident, often evaluated on a "case-by-case basis."
Direct vs. Indirect Human Error Examples:
Scenario 1: Direct Error (Self-Injury): If one spills a drink and then slips on it, it's considered their error.
Scenario 2: Indirect Error (Injury to Another): If one spills a drink and leaves to retrieve cleaning supplies, and another person walks in, slips, and falls, it is still considered human error. The initial spillage and the delay in securing the area contribute.
Safety Professional's Role: In such a company incident, a safety professional would ask detailed questions to understand the full context, such as why cleanup was delayed or why safety measures (e.g., mats) weren't in place.
Beyond Direct Human Error: Other Accident Causes
Machine Malfunctioning: Acknowledged as a potential cause of incidents that may not directly involve human error.
Environmental/External Factors:
Example: Power outages or lightning strikes.
Scenario: Lightning strikes a building, causing a power outage while a worker is operating a forklift to stack materials. The loss of light severely impairs visibility.
Nuance: If the worker continues to operate the forklift in the dark, the incident then becomes an example of human error compounding an external factor.
Prevention: While humans cannot control natural phenomena, they can implement controls like lightning rods or improved drainage systems to mitigate risks.
Systemic Failure of Infrastructure/Systems:
Example: A drainage system fails or is overwhelmed by heavy rainfall.
Significance: This illustrates that incident causes are not always "cut dry" or solely attributable to individual actions. Systemic issues or design limitations can be crucial contributing factors.
Contributing Factors: Worker Overload and External Pressures
Worker Overload / Production Pressure:
Concept: "Overload" or "worker overload" is identified as a significant factor in accident causation.
Example (Norfolk Southern Railroad Ties):
A company secured an urgent, massive order for railroad ties.
Norfolk Southern installed these ties, expecting them to last 20-30 years.
Within a few months to a year, a significant number of ties began to fail prematurely.
Investigation: Core samples revealed that the ties were improperly treated. The preservative (e.g., creosote) was not penetrating the dense heartwood as required, only treating the outer layer.
Root Cause: The intense production pressure to meet the large and urgent demand led to a deviation from the proper, time-intensive treatment process, resulting in defective products being installed.
Factors Contributing to Error: Demands of production, an increase in workload, deviation from standard patterns, and production pressure (expecting more output without increasing resources or time) are all identified as significant precursors to human error.
Ethical and Practical Implications: The Line of Responsibility
Medical Emergencies and Responsibility:
Question: If a worker suffers an unavoidable medical emergency (e.g., stroke, heart attack) that leads to an incident, is it considered human error?
Discussion: This brings up the complex issue of personal responsibility versus occupational responsibility.
Conclusion: If such an event is truly unforeseen and unavoidable, it often falls under the category of an "Act of God." These types of incidents are generally considered part of the approximately 10\% of incidents not directly attributable to human error, highlighting a tricky distinction in causation.
Avoiding Blame and Identifying Root Causes
The Principle of Not Assigning Blame Prematurely:
Scenario (Brake Failure): A driver experiences brake failure on a steep mountain road, leading to a fatal accident. Is it the driver's fault?
Instructor's Point: It is crucial never to assign blame immediately. Instead, a thorough investigation is required.
Detailed Investigation: If the brakes were recently changed, the investigation would then focus on the mechanics and the quality of their work.
Analogy (Falling Tree): If a tree unexpectedly falls on one's home and causes injury or death, it is not the homeowner's fault for not cutting it down, as it was an unforeseeable event.
The Ultimate Goal: The aim of accident investigation is to understand what causes accidents, why they occur, and which factors contribute. This knowledge allows for proactive prevention rather than merely reacting to consequences.
Incident Investigation: Methodologies
Domino Theory: Briefly mentioned as a theory suggesting that accidents and events are linked in a chain reaction.
The Five Whys (5Y) Method:
Purpose: A fundamental and straightforward methodology for identifying the root cause of an incident by repeatedly asking "Why?"
Process: The principle is to ask "Why?" at least five times (or until a root cause is found) to dig deeper than the surface problem.
Example Scenario (Arya Slips):
Why did Arya slip when she came to the door? (Because there was liquid on the floor).
Why was there liquid on the floor? (Perhaps a leaky pipe, or a spill that wasn't cleaned).
Why wasn't the liquid noticed/cleaned? (E.g., inadequate lighting, lack of regular checks).
Why wasn't a warning sign placed? (E.g., no procedure, signs unavailable).
Why is the drainage system (or plumbing) faulty or unchecked? (Connecting to systemic issues like the drainage example mentioned earlier).
A deliberately humorous extension involving a spider web causing a slip illustrates how seemingly minor details can expose systematic failures.
Key to the Method: The efficacy of the Five Whys technique rests entirely on how the questions are framed.
Guidance: If a question leads to an irrelevant or vague answer, one should rephrase the previous "Why" question to maintain focus and specificity.
Benefit: This method yields a far more comprehensive and nuanced understanding of an event compared to a superficial, "cut and dry" explanation.
Preparation for Future Labs: Students are encouraged to read Chapter 5 on incident investigation, practice the Five Whys method at home, and be ready for mock investigations in the lab setting.