A self-driving infrastructure grid will solve a lot of commuting issues by itself. Get rid of human reaction time, people driving diff speed limits, etc and the flow of traffic will be greatly improved. The issue, IMO, is how to solve for the bottleneck in this issue which is - entry/exit points. You can build all the tunnels you want but if theres only one exit and thats where everyone wants to go, then you're SOL. A roadway and a tunnel leading to the same location may cut traffic on each road by half but when they exit to the same spot, you'll lose all that saved time. I'm picturing him doing this in Boston and its just grossly unrealistic. Small city with crazy congestion but you cant exactly add a bunch of new exits off the highway into the city.