CO2 is an agreed problem and transport makes significant emissions. Electric or hydrogen power is necessary to eliminate local emissions, but any form of energy use causes CO2 emissions at generation, so minimum energy is vital. Aerial podcars use 8 times less energy than trains, and 10 times less than cars. Data source: Richard F. Di Bona, Ollie Mikosza.
Requirements: To reduce CO2 by 80% requires mode change away from cars and on to low energy, electric, aerial podcars.