Root cause of problems of the cities is that they are built too densely. There is no room for transportation, housing, industry and trade. Public mass transportation makes the problems worse. The prices of living and working spiral up. Subsidies require heavy taxation.
Suburban sprawl is the solution for all this misery. Just place the jobs and services where the people live. The need for transportation goes down. The usage of roads is more levelled. There should be no rush hours and congested areas any more. Traffic lights are replaced by roundabouts, bridges and tunnels.
Self-driving cars will become popular because there bring door-to-door transportation to everyone without a need to own a private car.
Saving in energy is not an end in itself. There is more to save in location based costs in housing, trade and industries.