BOS 4601 Unit VI Quiz

Explain the three steps in the fault tree process. What does each level represent?

Tree analysis is utilized to find connected factors that led to a particular incident or accident. Investigators use a graphic display of information to analyze human, equipment, or environmental systems and find paths to failure or success (Oakley, 2012). There are two basic types of trees used in accident investigations; Fault Trees and Analytic (developed) Trees.

Fault trees use a three step process wherein the key is to ask, “Why?” at each event in the tree to try to discover causal factors (Oakley, 2012). The first step is to start with the top event (accident, injury, or damage). Step two is determining the events necessary to produce the top event and the corresponding logic gates. The third step is to continue on this path until you reach correctable events (Oakley, 2012).

The general idea is to continue the tree until you reach a point at which there are no more events. The process of diagramming the accident from general events to specific events will help develop the causal factors of the accident (Oakley, 2012).

References

Oakley, J. S. (2012). Accident investigation techniques: Basic theories, analytical methods, and applications (2nd ed.). Des Plaines, IL: American Society of Safety Professionals.

What are some of the problems associated with using cause and effect analysis?

Cause and effect analysis is a structured approach to determine the causes and effects of events that led to the accident being investigated (Oakley, 2012). While there are several types of cause and effect analysis used in accident investigations, a process used often is the Apollo method and Ishikawa fishbone analysis.

One of the issues associated with any casual factor analysis is knowing when to stop (Oakley, 2012) and those who utilize cause and effect are not immune from this issue. Some of the problems with cause and effect are; stopping too soon for superficial causes, the need to place blame, not having enough facts of the accident or starting before they are known, and not looking at all the issues such as policy, management, training, supervision, human factors, etc (Oakley, 2012).

Reference

Oakley, J. S. (2012). Accident investigation techniques: Basic theories, analytical methods, and applications (2nd ed.). Des Plaines, IL: American Society of Safety Professionals.

What are the three types of tree analysis? Briefly describe each.

One of the three types of tree analysis is the Fault (or Negative) Tree. This type of tree analysis is generally used to determine failures within a system. They are also used to determine failure rates, troubleshooting, and risk analysis. It was developed for the US Air Force in 1962 (Oakley, 2012).

The second type is the Positive Tree. Positive trees display a system graphically from specific to general information and is a useful way to map components (Oakley, 2012). Positive trees can be developed early in design before an accident occurs. When an accident happens, it can be compared to an Analytic Tree to find the failure or problem.

The third type of trees is the Analytic (Developed) Tree. Examples of this type of tree are MORT, PET, and typical flowcarts. These types of trees can be utilized to show a system’s structure in a graphic format. In accident investigation, the analytic tree is used by the investigator to trace back and find faults or problems (Oakley, 2012)

Reference

Oakley, J. S. (2012). Accident investigation techniques: Basic theories, analytical methods, and applications (2nd ed.). Des Plaines, IL: American Society of Safety Professionals.

What are the three types of cause and effect analysis? Which one do you think you would choose for an accident involving a forklift striking a worker who was walking across a warehouse? Briefly explain your choice. 

The three types of cause and effect analysis are the Apollo method, Kaoru Ishikawa’s Fishbone analysis, and the 5 Whys or Questions of the Void (Oakley, 2012). The 5 Whys is used by looking past the observed symptoms to find the root cause of the accident. The investigator solves a problem by repeatedly asking, at least five times, why the problem or accident occurred and why that cause occurred. While not as precise of a technique as the others, the 5 Whys is effective if the investigator has in-depth facts pertaining to the accident (Oakley, 2012).

The Apollo method is a software program that leads the investigator through the approach with an effect followed by at least two causes. According to this method, each time the investigator asks ‘why’, he/she should find no less than two causes, and then two more, and so on (Oakley, 2012).

The Fishbone diagram has been used for years and looks somewhat like the skeleton of a fish when completed. In the above scenario, if I were the investigator, I would utilize this form of investigation. The fishbone focuses on finding the cause(s) and groups them into categories (Oakley, 2012). As such, it would be easier to graphically explain why the forklift driver did not see the worker and what happened when the worker was too close to where the forklift was operating.

Oakley, J. S. (2012). Accident investigation techniques: Basic theories, analytical methods, and applications (2nd ed.). Des Plaines, IL: American Society of Safety Professionals.