I've got a version of Heathrow AFCAD that I've modified to more closely resemble the actual airfield. As a result, there are a few taxiways which I've designated as closed. But I was surprised today to see aircraft taxying to the runway along the closed taxiway.Any ideas???

The Closed indicator means nothing to AI, it merely puts a check mark on the taxiway. What I usually do is break the taxiway link leading to the runway.Delete the taxiway node that is hooked to the runway taxi link (black line on runway).Reconnect the two runway links.Place a new taxi node slightly to the left or right of the new runway line.Reconnect the taxiway to the new taxi node.Fill in the taxiway designator if there is one.Check to see if the characteristics match the rest of the taxiway. Lights, lines, surface, etc.You can still designate it as closed if you like.