I run a very large route (667 baseboards) with multiple routes and 20+ trains. When I just observe the AI drives ok. But When I take control of a train and drive about an hour I observe that some trains just stop even on simple routes with no switches. I have a loop line and the trains seem stuck sometimes in between signals. I think Dermmy is right and the cause is that there is too much CPU load. Does Trainz see each consist as a train (even if it's stationary with no AI attached to it?). Or does it work different. Anyway. If I just observe it drives ok but I think I will try to limit the active consists on my route.