What if we just took the bulk of the transportation routes in a city and put them underground so they weren’t in everyone’s way, and we could use all the above ground space for walking and other pretty stuff? Said London in the 19th century. 

The City of Pittsburgh closed Bigelow Boulevard in 1996 for 29 days. Then-Mayor Tom Murphy said they felt closing Bigelow “would make for ... a more attractive campus.” The trial program didn’t...