System Safety for the 21st Century, 2nd Edition

CHAPTER 20Event and Causal Factors Charts

The basic concept from which event and causal factors charts were developed can probably be traced back to Ludwig Benner and others at the National Transportation Safety Board. Benner developed a very similar technique called multilinear event sequencing (MES) and, more recently, sequentially timed events plotting (STEP). Event and causal factors charts were part of the overall MORT approach to system safety developed by W. G. Johnson for the Atomic Energy Commission in the early 1970s and further developed and taught by the Department of Energy’s System Safety Development Center (SSDC). The use of the event and causal factors chart is sometimes referred to as causal factors analysis.

Event and causal factors charts are graphic representations that basically produce a picture of an accident—both the sequence of events that led to the accident and the conditions that were causal factors. This tool works very well in conjunction with PET or MORT analysis.

Unlike PET, MORT, and mini‐MORT charts, which are working papers to be filed with backup documents or discarded after use, the event and causal factor chart is an important descriptive tool. An “executive summary” version of the larger, more detailed chart developed during the investigation is included in the formal accident report as an illustration. The event and causal factors chart aids initially in collecting and organizing evidence and in developing an understanding of the accident ...