Ideally you would have to change how zoning and planning works to create denser more integrated neighborhoods that can be efficiently used with public transit.

If that's too difficult the next best compromise is a park-and-ride scheme. Put a couple stations with huge parking lots in strategic locations between suburbs, and offer good rail or subway connections to work places and shopping destinations. That doesn't enable anyone to get rid of their car, but it gives people a faster alternative to the most congested roads