This is quite possible for Manhattan and probably for other cities. Manhattan once had transportation needs for streets since it was ringed with wharves for sea

This is quite possible for Manhattan and probably for other cities. Manhattan once had transportation needs for streets since it was ringed with wharves for seaborne and river commerce, had huge warehouses, railroad yards, factories, and all the facilities of a dynamic manufacturing city. That has all disappeared and the Manhattan economy is essentially services for residences, entertainment, media, finance, government, hospitals, etc. Production of goods is minor, and distribution and warehousing have mainly moved out, e.g. Fulton fish market. So Manhattan becomes a forest of towers mainly for residents and offices, with some more specialized buildings for hospitals, conference centers, sports venues, etc. But there is even little need for retailing space, since the distribution centers for online retailers serving Manhattan can be in the outer boroughs or NJ. In this scenario the transportation system boils down to distribution of food and other goods to the towers and the collection and removal of garbage, plus mass transit intra island and to/from the hinterlands for commuters to the office towers, as well as mass transit to/from airports for the tourism and business travelers. Manhattan is probably ahead of other cities in becoming a pure center of goods consumption.