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the degradation of a man-machine system. The basics steps to mitigate and
prevent human errors are the following:
- List and analyze human operations
- Estimate the error probabilities
- Estimate the effects of human errors on the system failures
- Estimate working environment
The basic model of human behavior is shown in 2.
Fig. 2. Human Behavior State Model
Human Error Modeling is a complex task that depends on a set of or-
ganizational, qualification and control aspects. Several conditions must be
taken into account during the evaluation process: the administrative control,
a special qualification for the task, the working environment, and stress. The
results depend on component complexity, time and personnel availability,
administrative control, supervision and qualification for each personnel, and
level of communication between them.
The influence of human behavioral affects transportation process as safe-
ty-critical component. Stimuli that have to be recognized include physical
and operational environment to which human are exposed. In response to a
given stimulus or set of stimuli, humans recognize the need to perform a given
action. If such recognition is not made, then an error of omission occurs. As
a result, the undesired event succeeds and the accident begins. The sequence
can be represented graphically by using the Event Trees built on the basis
of statistical information. The branches represent the erroneous actions - Pe
and the successful human action - Ps. All probabilities, except those in the
first branching, are conditional probabilities.
Other well known techniques to model human error are Petri Nets, Markov
Trees, and Fault Trees. Fault Trees do not represent dependencies among hu-
man actions. Human behavior can be accurately described as a set of dynamic
modes through the dynamic Markov models. Markov chains have been used to
model human behavior in controlled or uncontrolled situations. The param-
eters of the model must be estimated from data. The estimation procedure
assumes that the observed process is stationary.
Humans must recognize the need to perform a given action. If such recog-
nition is not made, then an error of omission occurs. Such an error is denoted
