Hands down, THE best Railroad Tycoon-inspired game available right now. And I've played a lot of them. It's extremely satisfying when you reach the point of being able to establish transit hubs.

Once you get through the SUPER buggy tutorial, the game really comes into its own. I am not a scenario guy at all, I live entirely in a Challenge mode, which is basically a sandbox with all the normal restrictions of money, research, and unlocks.