I've printed out about 4 of these so far. Pictured in Red is PETG and it is stretched out to be a little bit taller. I made a bit taller because my kids started loading cargo on their trains and I made some more room for that.

Print Vertically as shown with no supports needed. I designed the tunnel a little thicker to withstand toddlers.

Feel free to shrink and stretch out the tunnel in your slicer however you like. My 2 toddlers love the tunnels with their train sets.