Dancing Hoskuld
Deity
I've never liked how that chain works. Personally, I feel that railways should be extraordinarily expensive per space and a player should be informed that their intent is NOT to cover every space and that they should wait for Highways (to get roughly the same amount of movement on the rest of the spaces) and just use Rails to connect cities and to aid mines and lumbermills.
Better still is if we could split rails and roads into two differing path types that can co-exist...
That is not the way Civ routes work it is not a Railroad game. Anyway until someone fixes the pathing mechanism you are going to have to put the fastest route on every tile anyway. Yes Koshling has done great work on the pathing mechanism but it does not work for stacks containing different units. It also has a tendency to avoid ending a a turn inside a city preferring to go around it even if it adds a whole turn to the total move.