Originally Posted by chewybrian

It seems next to impossible to 'fix' existing cities, with the possible exception of someplace like Detroit, where you can realistically afford to demolish and rebuild large areas.

If you were making a new city, I would have a few suggestions:

Make more one way streets to save space and costs.

Design smaller yards offset by neighborhood parks. Would you give up 10 feet off your back yard in exchange for a large park nearby? Front yards, in particular, seem like wasted space in many cases--seldom used. Another ten feet there would add up quickly. Common walls between units minimizes building and heating and cooling costs, and saves a lot of space, too. Again, some would consider it a loss, but the room and money saved could easily be used to create more common green spaces and bike and pedestrian trails.

You don't have to make laws controlling people's choices, but some tax incentives could be used to push people in those directions. Larger lots create extra costs for the town or county, so pass on that cost to those who still want the big lots.

Mixing zoning spaces in a checkerboard pattern could help to minimize trip distances, which in turn could mean fewer roads and lower costs to taxpayers.

Cul de sac communities are the norm here, yet few are connected to each other. It's fine to funnel the cars back out to the main streets, but the foot and cycle traffic should be able to cross to the next neighborhood across the drainage ditch or through the wildlife area (kinda Florida specific here). In this way, you could travel across town on foot or by bike with only an occasional crossing of a busy street, ideally by over or under pass.

That's all that jumps to mind. Of course, in my ideal town, the bike paths would go through every park and connect every neighborhood, and allow access to the back side of businesses in the commercial areas. Free underpasses for everyone!