I'm confident that some reduction of paved surface can be achieved in most or all cities, but I think your tone is making the situation seem a bit more ridiculous than it actually is. I would expect a significant portion of any densely populated city to be paved, for the simple reason that people need to be able to get to essentially every part of a city. Short of more fanciful solutions like fully elevated or underground passageways, you're going to need roughly the same grid of roads even if you eliminate cars. Granted, you could theoretically get significant constant factor reduction in the width of roads if you can remove lanes (through banning cars, encouraging carpooling/public transit, or increasing bicyclists and pedestrians).
Of course, wide streets predate cars. Both Chicago's and NYC's street grids, with their wide avenues, predate the era in which everyone had a personal automobile. But take a look at older cities with narrower streets. You can get around Center City Philly, but the streets are so narrow in parts you barely notice crossing them.
> Short of more fanciful solutions like fully elevated or underground passageways, you're going to need roughly the same grid of roads even if you eliminate cars.
Not actually true. Grids come in many different shapes and sizes. As one easy example: the block size. As a city planner, you can choose any block size you like, and this will adjust the ratio of real estate to transportation infrastructure accordingly.
Additionally, and this is fanciful futurism more than anything else: in a city that functions without ubiquitous private vehicle traffic, you can make the roads narrower, which also increases the real estate. To take an example from where I live:
Potrero Avenue in SF is 100 feet wide. A hundred feet. If you naievely parceled this land out by drawing a line across the road every 5 feet, the each demarcated space would be worth $2k/mo rent. In a hypothetical future city without cars, you wouldn't need a road to be a hundred feet wide.
Agreed, the trick is to ban parking and narrow the roadways a lot. A few months ago this [0] was on HN and I was very convinced by its arguments pertaining to automobiles and urbanization.
Like Venice, Hamburg could use its vast system of waterways for transportation. If it's going to happen in any European city, I think Hamburg is one of the most logical options. It is after all, often referred to as the Venice of the North.
