Causal tree

The earliest logic trees were based on engineering fault tree analysis methods. Today, companies use a number of variations or combinations of logic trees and call them by different names, such as Why Tree,< 9) Causal Tree,(20,21) Cause and Effect Logic Diagram (CELD),<22) and Multiple-Cause, Systems-Oriented Incident Investigation (MCS011).<23,24) tools have more similarities than differences. 

Causal Trees were developed in an effort to use the principles of deductive logic found in Fault Tree but make it more user-friendly. Originally, private companies developed the Causal Tree Method (CTM) for safety, process safety, and environmental incident investigations applications. Rhone-Poulenc, for example, was an early user.<20.21) Multiple-Cause Systems Oriented Incident Investigation (MCSOfl) is another name for the CTM. At this time, most companies use simplified versions of fault trees for complex incident investigations. 

Causal tree methods rely on group discussion among experts from different fields, including workers, witnesses, supervisors, and process safety specialists. Starting at the end event, and working one level of the tree at a time, the group asks three questions ... 

Causal trees may be drawn from top to bottom, left to right, or right to left. Connectors such as AND- and OR-gates are often omitted. Some methods use only AND-gates. 

Boissieras, J. Causal Tree, Description of the Method. Princeton, NJ Rhone-Poulenc, 1983. 

Many deductive investigation techniques use logic tree diagrams. A partial list of these methods includes fault tree analysis (FTA), causal tree... 

The committee s analysis was conducted on several levels. First, members investigated the causal factors for each of the seven events listed in Tables 2-1 and 2-2. They then developed a notional causal tree for each of the two events in Table 2-2 that were analyzed in depth. For illustrative purposes, a causal tree developed by the committee for the December 3-5,2000, incident at JACADS appears at Appendix F. The tree is a standard tool in reliability analysis and is particularly useful in human reliability analysis where operator actions contribute either positively or negatively to an incident. Lastly, the committee provides a series of general and specific observations about the events. 

FIGURE F-l Causal tree for December 3-5, 2000, JACADS event. 

In our experience, methods like the causal-tree analysis, management oversight and risk tree (MORT), and the fishbone diagram are all suitable for... 

The investigation-system style we prefer is one that uses free-flow logic that documents the relationships among the facts of an event. These are usually referred to as causal-tree diagrams. We prefer strong logic theory and a... 

The inquiry should include a root-cause analysis of a number of incidents, looking for patterns. This increases the probability that the behaviors are indeed critical. We would add that most of the hundreds of incident investigations we have seen do not get to root causes. Krause is clearly aware of this and provides an excellent methodology to improve this process. He recommends the causal-tree method. This particular method for incident investigation is described in Chapter 5. 

Instead of falling into old baggage discussions,. .. I can stay focused on the facts and avoid coming to the wrong conclusions. You might even say it is something similar to a personal-type version of the causal tree. 

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