Using dirt and sand instead of loads of expensive concrete for a viaduct or faunaduct. There's only logic with this design. More green, less concrete, cheaper, long lasting yet easily changed (like widened or moved) or removed if needed in 20, 40 or a 100 years. Concrete can crack. Plant trees on this and the roots will only make it stronger and longer lasting. The American way of using concrete everywhere really is the worst thing you can do. Look at the Netherlands, the best infrastructure in the world with the least amount of concrete. Build smarter, not bigger.