I've been seeing these flimsy looking overpasses getting put together. Back in the day, they used to pour out huge, solid slabs of concrete footings and wide, solid concrete columns to support the overpasses, but not so anymore.

I'm seeing this design which uses concrete "tiles" for lack of a better term. These tiles are approximately 5 inches thick and approximately 8x12 feet in size.

What they're doing is piling up dirt and using the tiles to surround the dirt on all sides. It kinda looks like the tiles may lock together at each edge that touches.

It does not look like a design that would have long life, but it sure looks like it saves money.