bridges and tunnels

My idea is : instead of digging trenchs in mountains to build road through a mountain and stacking dirt and rock in the sea to build a bridge to join a smaller island or something else i was wondering that it would be nice to have placeable buildings to do this properly.
For example, to build a tunnel, il would be cool and realist to be able to place a building like a hollow concrete structure. At first the trucks are delivering the materials to build the first section of tunnel, then with an available excavator to assign, digging the rocks inside the first section. Once the first section is fully empty, the cycle repeat itself.
For the bridge, i imagine something more usual in the game, like a placeable building allowing the vehicles to cross water or to pass above a gap.
For both of these, tunnels and bridges, i think it would be cool to use them with placeable roads.
Sorry if i made english mistakes :)

Einen Tunnel bauen zu können wäre in vielen Fällen eine Erleichterung. Anders herum kann das Gestein abgebauter Gebirge und Gelände-Terrassen gut dazu verwendet werden die Insel zu vergrößern und/oder Wasserstraßen zuzuschütten bzw. Inseln zu verbinden.

Trains typically can only surmount grades less than 3%, this is primarily due friction coefficient of steel to steel. That friction is not solely determined by the weight of the truck (engine), number of drive wheels and carriage (haulage - cargo, number of container cars). Play a railroad simulation to gain insight how important tunnels are to trains. These railroad sims, often allow more trucks (engines) but even this has limits.
Waterways without bridges, that's beyond absurd. Build a long filled connection between to waterways is absurd. Add research Bridges and perhaps Tunnels (separately).

I think this would be a great option where to open pit mines can have a tunnel between them and if persay one floods so does the other. Bridges is also useful for getting across to the other island