&#62; reorganizing a major urban area to be walkable takes decades<p>It seems to take about 15 to 20 years.  The dense walkable urban areas in Northern Virginia and Maryland grew up around the metro system in that time frame.<p>Large areas don't actually need to be reorganized, just refurbished.  Many cities including philadelphia, baltimore, and DC to some extent have loads of developed space that's just low rent and crime ridden.  Just put back in the streetcars that were ripped out in the 60s, fix-up the buildings, and price out the gangsters from living there.  That's basically the story of NYC's rehabilitation in the 90s, except they didn't need streetcars.