oh okay i figured it out, i totally didnt notice the train only needed to make one pass so it's okay if the bridge is "one-way"....
I can't figure complex level 9 out! there are no anchors on the banks at all. i've tried building a funky swinging thing, so the train basically jumps onto the tracks and then leaps off the other end, but i cant seem to make it strong enough to survive this brutality. any picture of a completed complex 9 would be helpful, thanks.