Situation: failure of a warning system
Features of a warning system failure.
(1) temporal mode
(2) nature of the failure
(3) underlying cause
Temporal mode:
(1) temporary (for example, a power outage)
(2) permanent (for example, destroyed)
Nature of the failure:
(1) warning covered or masked or otherwise non-functioning (present but not working)
(2) partially or completely removed (not present)
(3) design problem (present and working but ineffective)
Underlying cause of the failure:
(1) environmental conditions
(2) intentional
(3) unintentional (accidental)
(4) mixed (a sign may deteriorate in the environment due to a maintenance decision)
