Rail - This transport method is efficient and traffic free. You must carefully place your rail depots, else the rail will go unused.
Subway - These are underground railways. They operate like rail, except that subways need subway stations to operate.
Rail Depot - This is where commuters enter and exit the rail system.
Subway Station - This is where commuters enter and exit the subway system.
Sub/Rail Juncture - This allows you to connect your above ground rail with your below ground subway. You must place this next to an existing rail line.