As a car guy first and gamer/computer nerd/audiophile second through fourth in... some order (not that I care, I know what's first, that's what counts) I say whatever city anyone wants to design, throw in this street design: no street signal lights, no stop signs, and no roundabouts. Insanity, you say? No, just not fully explain yet. In my area, we have far to many railroad tracks. Some genius a while back decided that while rebuilding the roads, make the road an underpass and the railroad track an overpass. I say this should be done at every major intersection in this Utopian paradise we're looking to design (with gentle flowing curves to get from one road to another should you wish to turn). As for the further insanity of no lights or stop signs, I call for the underused "yield sign". No one's coming your way when you go to turn? Just keep going. That's bound to boost fuel efficiency, or, if we go all electric ([a href=http://www.teslamotors.com/]Tesla![/a] Woo!), extend your battery range because you're not slowing/stopping/accelerating back to speed over and over and over...
Okay, that might not work with the barge-based country proposed by meatloaf231 (and, some time back, Dogbert), but so long as I can get where I'm going with a minimum of delay, I'll be a happy camper.