Hello,
I wasn’t sure whether this is modding or support, but seeing that it’s a completely new game element, I’ll post it here. It would be nice to be able to build viaducts. It saves so much space in cities compared to piling up earth, thus it’s cheaper and actually quite realistic. Streets can easily be crossed by a small bridge, connecting the viaducts (it should look basically the same). And then, the same goes for going below earth level: Instead of having incredibly huge margins at both sides, which happens, when you take a track beneath the ground level, you could have steep stone walls on each side, again saving space and making it look more realistic, also when going underground at some point.
I hope that at some point this will be included, because it’s a pain when it comes to collisions with highly piled up earth…