Put the little people in the cars - then they will move !!! Trainman2001 - did you watch the video posted by Engineer-Joe ? Some of the turns made by the car were pretty tight I thought.
I have some of the cars I got from the same people (very nice by the way) so I just ran downstairs to see how tight a circle I could get and have the cars run reliably. I did a circle with a 11.5 inch diameter and they ran perfect. Then I did a circle with a 10 inch diameter which is the smallest the steering would allow and the car would leave the circuit. My circle might not have been perfect as I quickly threw it together for the run.
That brings me to the next item. You don't have to use the pre-made track which can get costly with a large layout. They do sell special wire that comes in 33 foot lengths and you can free form your roadway like I just did and that costs like .50 a foot. The wire sells for $18.00 for a 33 ft roll. I purchased it from the same people. You are supposed to cut a small groove in your surface ( and yes they sell a special tool that cuts that groove) and you only cover it with paint.
You can also add magnets and reed switch sensors on certain cars only to make events happen which really puts it over the edge - similar to what Lionel is doing. OK - time to stop rambling. Give them a try - its fun ! JP