ABSTRACT
Fault tree analysis (FTA) is a graphical method commonly used in both reliability engineering and system safety engineering (though it is more well known in reliability circles). It is a deductive approach that is very powerful as a qualitative analysis tool that can be quantified. You postulate a top event-or fault-such as train derailment, then branch down from the top event, listing the faults in the system that must occur for the top event to occur. This top-down method forces you to go through systematically, listing the various sequential and parallel events or combinations of faults that must occur for the undesired top event. Logic gates and standard Boolean algebra allow you to quantify the fault tree with event probabilities and thus determine the probability of the top event.
