not quite getting the big picture.
as a subway with 1,000 stops it sounds annoying. you don't generally want your ride to lose momentum. and if the stops are so close, you need to think about just walking.
but maybe it's for cars? then what are the logistics of a small space and getting off/on?
The big picture, is he's testing the technology for Mars.
All Elon Musk projects are related to Mars - Tunnels, Solar, Electrical Storage/grid, Electric Vehicles & Rocket Ships.
I expect him to get into the 3-D Printing Construction business next.