You could decide to have 5 floors of garages from the ground floor up, and have 5 floors of roads to drive on (especially easy if you make it electric only for

You could decide to have 5 floors of garages from the ground floor up, and have 5 floors of roads to drive on (especially easy if you make it electric only for most vehicles - maybe confine heavy diesel vehicles to the ground floor with appropiate ventilation) Then on the 6th floor have a pedestrian/cycle floor that's sheltered from the elements, and the 7th floor have open parks, with 30 stories of housing and offices above.