I have a very large circular build with a 'donut' arrangement of minecart tracks (id 24 blocks od 44 blocks).  Within this 20 block wide 'crust' run thirteen minecart tracks laid out adjacent.  Each track has a single hopper car.  They start and stop along a common line that is normal to the circle (as close as you can get with blocks anyway).  I am having minecarts 'jump' the tracks so that I end up with an empty loop and two carts on another loop.

1.  How to duplicate:   You really don't want to.  I am five days into this thing and less than half done but the description is above.

2.  What I expect:  Each car to stay on its own track.

3: What is happening:  Cars are switching tracks