I think I didn’t have enough tunnels in this game. I tried several combinations, but it seemed like there was no way to link both the circle at the top and the triangles on the right and the special shapes on the islands. There was always one river crossing too many. I had already passed 2 or 3 weekends, and none of the upgrades available were tunnels.
I had the same situation as you, but I still managed to get pass that hurdle. To do this, you will need to “juggle” your lines among the stations, until you can get the Tunnels upgrades.
Yup, St. Petersburg is the one city that we’re sure is too mean on tunnels. I needs one more crossing, and evening out the kink on the east of the river.
I’ve added one extra tunnel for now, we’ll take a look at it again before release.
I got 734 passengers deliverd and had that problem