i think it could be very simple if rails were an upgrade from expressway, once it becomes a railway then ya, it be cool to show on a map of course you need to build a hub, this is not a station but it allows rail lines to connect and in here you can 'barricade' or lock a connection to prevent trains from a certain place from going through.
then you need to make a station which would be under transportation subheading of buildings
then we have to build our train engine and rail cars
you can make connecting rails by upgrading the linked expressways and building a station somewhere else along the line, there the train can stop, load/unload, refuel, take another path to any other linked station if there is one.
nobody would be building stations in every town as say one major city wants to connect a rail line to another major city that they have good relations with, they would build connecting rail lines across the map, and have a station at each end, and the train engine operator gets the option to drive directly there, but of course, we'll need to make it at least as fast if not faster than current vehicles, because the weight effect of having a couple loaded cars will bring it down in line, or we could have different types of train engines, the intake of which is different along with their speeds
diesel engine, coal engine(or charcoal), gas(propane) engine,
and i guess if we wanted to throw in a twist, make em take water for the steam
here we solve the problems of messy lines going every which way because they would just follow the path roads do and not criss cross
we solve the problem of one country isolated from another by a hostile neighbor in between, because you would have to have the lines connecting and the neighbor in the middle could just not allow the lines to cross it's borders or alternatively, allow to barricade/lock a particular connection this could effectively stop trains from crossing between those two isolated countries, if all the rails crossing the border were locked 'barricaded' the option to go to a particular station would not exist or it would be greyed out because the connection is blocked.
the rail upgrade from expressway would need timber(or treated wood? wood mixed with resin?), limestone and stone, sand, iron, steel
the hub, would be mainly stone with a bit of iron
the station would be more stone and more iron/steel, maybe wood?
if you really wanted to throw in more complexity, you could make it possible to have seperate parallel rail lines, by making it mandatory to make the hubs before the rail upgrade, the rail line connecting 2 hubs, then when building a station, either have to choose which hub it is connected to, or build it in the hub, if you are in the station or hub, you should be able to walk to the next town (not restricted to stations because a walker can stop at a hub),
the train engine would be lockable of course, and each car could be locked, through some passenger cars might be left open, who knows, maybe we'll have trains with 10 cars and someone forgets to lock one and a hobo hops in just as it's about to pull away
