When vault city caravan is under attack it calls to vc and tells what's going on. That's why players lose vc rep if they attack its caravans. What if everyone being a vc citizen and having a radio could get this call, get a green circle on their map and go help their fellow npc citizens? This would only apply when vc patrol/caravan was actually attacked by a player. The radio message could tell how many players are attacking to prevent false alarms.