I agree, rail is the most efficient way to move large numbers of people, and a very important tool for enabling high density development. But a good transportation system includes a variety of modes and a well connected network. To support rail, you also need a suite of smaller vehicles that can take people off those main trunks. One without the other is an incomplete system. And of course you can't have any of that without a complete network of pathways, sidewalks, bike infrastructure, streets/roads/highways, etc.

Oh, and fares should be payable in Sats.