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This material is for training purposes only. Its purpose is to inform employers and employees of best practices in occupational safety and health and general OSHA compliance requirements. This material is not a substitute for any provision of the Occupational Safety and Health Act or any standards issued by OSHA.
 MODULE FOUR: CONDUCTING AN EVENT ANALYSIS
Introduction
This module introduces you to the concepts of assessment and analysis as they relate to the accident investigation process. We'll review some theories of accident causation and discuss the process of developing and analyzing the sequence of events occurring prior to, during, and immediately after an accident.
Sorting it all out...
We've collected a lot of factual data and it's strewn all over the desk. The task now is to turn that data into useful information. We've got to somehow take this data and make some sense of it. It's important to know that we are not just conducting an "assessment" to determine what actors and acts were present. More importantly, we're conducting an "analysis" to determine specifically how system weaknesses interacted with those actors and acts to cause the accident.
Analysis defined
Webster defines analysis as the, "separation of an intellectual or substantial
whole into its parts for individual study."
When there is a workplace accident we need to separate or "break down" the accident process (the whole) into its component parts (events) for study to determine how they relate to the whole. Since the accident, itself, is the main event, its component "parts" may
be thought of as the individual events leading up to and including the main event or the accident. The accident investigator's challenge is to effectively assess and analyze each event to determine if and how it contributed to the accident. To do this we need to makes assumptions about what causes accidents...why they happen.
Why accidents happen
Over the past century, safety professionals have tried to more effectively explain how and why accidents occur. As you will see below, their explanations were at first rather simplistic. Theorists gradually realized that it was not sufficient to explain away workplace accidents as simple cause-effect events. The developed new theories that better explained the complicated interaction among conditions, behaviors and systems that result in an accident. Let's take a look at some of these theories.
- Single Event Theory - "Common sense" leads us to this explanation. An accident is thought to be the result of a single, one-time easily identifiable, unusual, unexpected occurrence that results in injury or illness. Some still believe this explanation to be adequate. It's convenient to simply blame the victim when an accident occurs. For instance, if a worker cuts her hand on a sharp edge of a work surface, her lack of attentiveness may be explained as the cause of the accident. ALL responsibility for the accident is placed squarely on the shoulders of the employees. An accident investigator who has adopted this explanation for accidents will not produce quality investigation reports that result in long-term corrective actions.
- The Domino Theory - This explanation describes an accident as a series of related occurrences which lead to a final event that results in injury or illness. Like dominoes, stacked in a row, the first domino falling sets off a chain reaction of related events that result in an injury or illness. The accident investigator will assume that by eliminating any one of those actions or events, the chain will be broken and future accidents prevented. In the example above, the investigator may recommend removing the sharp edge of the work surface (an engineering control) to prevent any future injuries. This explanation still ignores important underlying system weaknesses or root causes for accidents.
- Multiple Cause Theory - This explanation takes us beyond the rather simplistic assumptions of the single event and domino theories. Once again, accidents are not assumed to be simple events. They are the result of a series of random related or unrelated acts/events that somehow interact to cause the accident. Unlike the domino theory, the investigator will realize that eliminating one of the events does not assure prevention of future accidents. Removing the sharp edge of a work surface does not guarantee a similar injury will be prevented at the same or other workstation. Many other factors may have contributed to an injury. An accident investigation will not only recommend corrective actions to remove the sharp surface, it will also address the underlying system weaknesses that caused it.
Developing the sequence of events
Our challenge at this point in the investigation process is to accurately determine the sequence of events in the accident process so that we can more effectively analyze the accident process. Once the steps in the process are developed, we can then study each event to determine related:
- Hazardous conditions. Things and states that directly caused the accident.
- Unsafe behaviors. Actions taken/not taken that contributed to the accident.
- System weaknesses. Underlying inadequate or missing programs, plans, policies, processes, and procedures that contributed to the accident.
We'll study these in the next module.
The final event in an unplanned process
When we understand that the accident is actually the final event in an unplanned process, we'll naturally want to know what the initial event was. When the initial event occurs, it effects the actions of others, setting in motion a potentially very complicated process eventually ending in an injury or illness. The trick is to take the information gathered and arrange so that we can accurately determine what initial condition and/or action transformed the planned work process into an unplanned accident process.
Remember, that in the multiple-cause approach to accident investigation, many events may occur, each contributing to the final event. For instance, if a supervisor ignores an unsafe behavior because doing so is not thought to be his or her responsibility, the failure to enforce behavior represents an event in the production process that may contribute to or increase the probability of an accident.
Each event in the unplanned accident process describes a unique:
- Actor. An individual or object that directly influenced the flow of the sequence of events. An actor may participate in the process or merely observe the process. An actor initiates a change by performing or failing to perform an action.
- Action. Something that is done by an actor. Actions may or may not be observable. An action may describe something that is done or not done. Failure to act should be though of as an act in itself.
It's important to understand that when describing events, first indicate the actor and next tell what the actor does. Remember, the actor is the "doer," not the person or object being acted upon or otherwise having something done to them. For instance, take a look at the statement below:
"Bob unhooked the lifeline from the harness."
In this example, "Bob" is the actor and "unhooking" is the action. First we describe the actor...Bob. Next, we describe the action...unhooking. The lifeline and harness, although "objects" are not actors because they are not performing an action. Rather, something is being done to them. Also note that the statement is written in active tense.
Sample sequence of events
To get a good idea what the sequence of events looks like, review the example below that was prepared for an actual fatality investigation conducted by OSHA a few years ago.
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Sequence of Events
1. Employee #1 returned to work at 12:30 PM after lunch to continue laying irrigation pipes.
2. At approximately 12:45 PM employee #1 began dumping accumulated sand from an irrigation mainline pipe.
3. Employee #1 oriented the pipe vertically and it Contacted a high voltage power line directly over the work area.
4. Employee #2 heard a ‘zap’ and turned to see the mainline pipe falling and employee #1 falling into an irrigation ditch.
5. Employee #2 ran to employee #1 and pulled him from the irrigation ditch, laid him on his back and ran about 600 ft to his truck and placed a call for help on his mobile phone.
6. Employee #2 than ran back to find employee #1 had fallen back into the ditch.
7. Employee #2 jumped back into the ditch and held employee #1 out of the water until help arrived.
8. Two other ranch employees arrived and assisted employee #2 in getting employee #1 out of the ditch.
9. Approximately one minute later, paramedics arrived and began to administer CPR on employee #1. They also used a heart defibrillation machine in an attempt to stabilize employee #1’s heart beat.
10. At approximately 1:10 PM an ambulance arrived and transported employee #1 to the hospital where he was pronounced dead at 1:30 PM. |
Paint a word picture
It's important that the sequence of events clearly describe what occurred so that someone who unfamiliar with an accident is able to "see it happen" as they read. If an event is hard to understand, it may be that the description is too vague or general. The solution: Increase detail. We can use two strategies to increase detail:
- Determine if anything else was said/done before or after the event your currently assessing.
- Separate actors. Remember, an actor may be a person or a thing accomplishing a given action. If an event includes actions by more than one actor, break the event down into two events.
We'll be covering causation, control strategies and system improvements in future modules. But right now, it's time to take the quiz, so let's go.
Take the Review Quiz
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