Zone
Whether a zone is free, spoken for, or covered.
Three states rather than a pair of booleans, because the invariants this subsystem must hold are statements about states and are far easier to assert when the state is a single value. The distinction between being claimed and being covered is the one that matters: a claimed zone is already unavailable to everyone else, but nobody's body is in it yet, so it counts against availability and not against coverage.
Covered, not occupied, and the word is chosen rather than inherited. Plain English calls a zone with three people standing in it occupied, so "occupied" is the wrong word for space a vehicle's body fills -- and it becomes actively misleading once a zone can hold a population that takes no exclusive claim at all. "Covers" is the word this subsystem's own prose has always used for a body spanning zones; the identifiers now agree with it.