Show a visual state model of the system that represents the state transitions and events in the gate control.

GateOpen $--($Train Detected$)-->$ GateClosing $--($Gate Fully Closed$)-->$ GateClosed $--($Train Detected$)-->$ TrainApproaching $--($Train Reaches Crossing$)-->$ TrainPassing $--($Train Fully Clears Crossing$)-->$ GateOpening $--($Gate Fully Open$)-->$ GateOpen

Any State $--($Error Detected$)-->$ ErrorState $--($Error Resolved$)-->$ GateOpen $($or other safe state$)$