I'm a doctor, not a mechanic
bLonelyZone
From Unreal Wiki, The Unreal Engine Documentation Site
A lonely zone is a zone that can never be seen from any other zones and from which no other zones (includes the sky box zone) are visible.
Lonely zones can be marked as such in Unreal Engine 2 by setting the bLonelyZone property of the ZoneInfo(U2, U2XMP, UE2Runtime, UT2003, UT2004) for that zone, so the engine doesn't need to consider any interactions between the lonely zone and any other zones.
