Design of a 100 mile subway might be 2 lines in each direction a fast and a slow. Fast might stop every 10 or 20 miles and run in the center. Slow would run in

Design of a 100 mile subway might be 2 lines in each direction a fast and a slow. Fast might stop every 10 or 20 miles and run in the center. Slow would run in an outer track that shares the other side of the fast track station platforms and would pick up and drop off at 1000 numbered stations on demand depending on what passengers enter on their smart phone ride apps.