The NYC subway accounts for 5 million trips each day, taking millions of cars off the road because they don’t need to exist in the first place.

Traveling with kids? Something people do with public transit and walking every day.

Promoting walking encourages healthy lifestyles; promoting driving (or just sitting in a car and not doing anything) encourages the opposite.

Elderly or disabled people take public transit all the time.

Short on time or carrying a bunch of groceries? Live out in the far suburbs? Then public transit isn’t for you. But it takes passengers who aren’t short on time off the roads, making your trip faster.

Edit: Cities with bad weather have adapted the cities to support public transit and walking (think covered, elevated walkways in Asia).

It’s not a zero sum game. Self driving cars will be great. Public transit is great (and can be great in more places 0if cities made more investment). Both can and should exist.