Want to ride in your own car on Amtrak? Try this.
Have someone book the Auto Train. Then go to the train with the person booked driving your car. Just before getting to the station, stop, climb into the trunk, and then stay there while the actual passenger gets out and your car is loaded. Then, when the train leaves, pop the trunk (all cars have a inside release for the trunk), and climb into the car, turn on the radio or CD player, and enjoy your ride on Amtrak in your own car! Then just before coming to the end, climb back into the trunk and stay there until your partner claims the car and you clear the station.
I'm still working on how to handle the essential bodily functions en route. That could be a problem. Until that is worked out, maybe this is not a great idea.
You know, in the entire history of the Auto Train and the two million or so cars carried in that time, I would not be surprised if someone, sometime actually pulled this stunt just to save a passenger fares. Wouldn't that be interesting.