I recall visiting Venice a few years back. I remember how peaceful and quiet it was, even though there were hundreds of thousands of tourists there.
I think this is just what the US needs - a brand spanking new CAR-FREE city. The Press would jump all over this. The city would have free advertising, just based on the novelty. I'll bet that if some entrepeneur started something like this, he'd get a ton of interest. This investor could purchase a large tract of land, near some city, and connect with a major Metropolitan area's light rail. And just like people must park their cars at the train station in Venice, they'd have to do this in Serenityville (how's that for a name?).
I found this link, and it has some interesting designs for Car-Free cities.
I'll bet there are a number of industries that would love to have their home-base in this kind of city. Not only would the city be quiet, but there would be NO auto accidents. To maintain the quiet atmosphere, I think internal combustion engines, in general, should not be allowed (gasoline powered lawnmowers, etc). I've attached a poll. I'm curious what others think.