Quote Originally Posted by Jay R View Post
They "acknowledge" it. They also research it.

Bridges cost 2-5 times as much as roads -- at least. They aren't going to build more of them unless you can show an economic benefit worth that much. A City Council who proposed it would be voted out for trying to raise everybody's taxes that much.

In my city (Dallas, TX) there are a few 5-high highway interchanges -- but only where it's justified. And those were by far the most expensive part of the highway system.

People who study, plan, and build roads for a living have actually thought about roads more than amateurs have.
What if they just bumped bikes and pedestrians up to the hypothetical other level, thus allowing them to expand the existing roads. This way the second floor would not have to support nearly as much weight and could presumably therefore be built much cheaper

Look at Disneyworld. Fisneyworld's all on the second floor.