model railroad simulators...

[Tyson Rayles]

Auran Trainz will let you build your layout your way, any size (if your computer has enough memory the sky is the limit) and any shape. Then you can drive your train from inside or outside the cab, do operating sessions or just cruise. There is plenty of support and add-ons as well. However as MountainMan said these programs can be addictive and you end up spending so much time playing with it that you don't get any real modeling done. These programs are handy for anyone who has disabilities that would prevent them from doing real modeling.