Board Game Arena

One thing I didn't see if it is explained - can you have a route going back on the same pieces that it already travelled?

Answer: Yes

I did some more playing and figured out that yes the shorterst path can cross over itself and also run back on the same track again.

If you mean that your train can do a loop and then return on the same route, yes.

Or if you mean can another play go the opposite route on the same route, yes.

I guess we can think of all roads as two lanes, you just can't cross over the line without a proper looped turn. Traffic can travel in both directions.