Imagine you had to plan a city where no more than 10% of all trips are done by car.
Either take an existing city and tweak it, or invent one from scratch. Let's say it has around one million inhabitants and ist mostly built on flat terrain.
What different modes of public transit would there be?

Certainly the networks would be a lot denser than in our cities, and public transport would be much higher in capacity. Could all the traffic in such a city be handled on foot, by bike and by metro/elvated rail? Or would there need to be other modes of transport as well?