The top event describes the point where we no longer have
adequate control over the hazard.
It is usually what we consider to be an unsafe state that is not yet an accident. Therefore, top
events while not being disasters themselves have the potential to become disasters if nothing is
done to control them.
In our driving a car on a busy motorway example, the top event could be described as losing
control of the car.
A point in time which describes the release or loss of control over a Hazard. The undesired
The top event is described as a loss of control event (not relevant to the Significant Seven)
but in a context of an undesired safety state. By defining this, we are able to consider multiple
potential causes for the loss of control and the various potential outcomes (as opposed to
considering just one fixed accident chain).
If you find that you are not examining the area you are most interested in, consider if it would
be reasonable to redefine the top event either left or right to suit your needs.
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