What’s better for climate change is less cars on the road, not underground roads. If we are going to be digging these expensive tunnels in every city they should be for subway systems. That would be a substantially better use of the funds and would be a good step towards reducing the emissions of a city. This is all assuming that we stop subsidizing car ownership so heavily of course.

The entire process of building and repairing roads is pretty carbon intensive due to the amount of concrete involved.