I don't want to hijack your path.
Don't feel like you have to... I only mentioned them earlier because you're the only person thus far in this world to do anything meaningful with rails.
I think the ultimate goal is to get to the Far South portal via underground pathways, then rise up to the hi-speed rails to continue south. You can start at the Far South Portal or start in Bradtropolis and get pie. Either or.
Actually, it might be even better to zig over near your place for a stop, then continue on the proper heading.