> what is needed is mass transit, Why mass transit and not walking more or personal blimps shaped like giant Trump babies? To make them more than your opinion,

> what is needed is mass transit, Why mass transit and not walking more or personal blimps shaped like giant Trump babies? To make them more than your opinion, you need to put some numbers on those statements. And the numbers work much worse than you think: between the low energy efficiency and low occupancy at non-rush hours, the massive infrastructure and the longer routes due to non-optimal layout, mass transit is better than American gas guzzlers but nothing to write home about. Here's some numbers put up by people who share your opinion - and that do not even take all these effects into account: https://www.citylab.com/transportation/2012/11/can-we-please-stop-pretending-cars-are-greener-transit/3960/ https://www.citylab.com/transportation/2012/11/can-we-please... So for in-city transport, mass transit is a hard sell on environment alone. (Intercity transport like trains are great though, and there is a strong convergence there, self driving cars pair well with fast trains, giving the best of both worlds: flexibility, speed and low footprint)