<P> The Human Factors Analysis and Classification System (HFACS) identifies the human causes of an accident and provides a tool to assist in the investigation process and target training and prevention efforts . It was developed by Dr Scott Shappell and Dr Doug Wiegmann, Civil Aviation Medical Institute and University of Illinois at Urbana - Champaign, USA, respectively, in response to a trend that showed some form of human error was a primary causal factor in 80% of all flight accidents in the Navy and Marine Corps . </P> <P> HFACS is based in the "Swiss Cheese" model of human error which looks at four levels of active errors and latent failures, including unsafe acts, preconditions for unsafe acts, unsafe supervision, and organizational influences . It is a comprehensive human error framework, that folded Reason's ideas into the applied setting, defining 19 causal categories within four levels of human failure . </P> <P> The HFACS taxonomy describes four levels within Reason's model and are described below . </P>

Where do the categories in the hfacs come from
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