This elevated highway is just a set of (badly textured) walls with YARN L4 DL3 -Si +Sh laid on top. The railings on top are a fair match for the yarn L4 bridge, and the road surface is, of course, the wonderful YARN original. That said you will probably want to burry the ugly part below that, so you might be better off putting the yarn road on a mound of raised terrain. This is far more common than slab sided concrete walls anyway.
It is however a bit more flexible than the yarn bridges, and could be useful for short elevation changes or sharp curves between bridge sections. I have recently discovered it is also a great way for a lazy person (like me) to hang a road on the side of a steep mountain, so I released it despite its imperfections.