Perhaps the "locked" state, since in any other state you are not yet done with the switch.
If the "locked" state is considered the final state,
then the strings accepted by the automaton show the positions of
the ignition switch from when you first insert the key up until you finally remove it.
For example, the string
IRRRLLLV
would correspond to a typical trip.
(The letters in this string are the first letters of the
state transitions in the diagram, with "V" for
the "remove key" transition.)
Clock time is not modeled in this automaton. In a typical trip, the ignition switch stays in the "run" position for most of the time, but automaton says nothing about that.
Other strings are accepted.
The string
IRRRLRLLLV
corresponds to a trip where the engine died once and
had to be restarted.
What string corresponds to an attempt to start a car that is out of gas? (There are many answers)