Maybe these maps will help answer your question, Mr. O’Keefe: https://www.csx.com/index.cfm/customers ... ance-maps/
Why does it need to be double stack autos? 125 mph capable single level would open up anywhere on the NEC.
A train limited to 30 cars would be presumably 1/2 the capacity of the Auto Train, but as a start up , so what ?