Beginning in the 1950s, cities demolished thousands of homes in walkable neighborhoods to make room for freeways.
At the time, this was seen as a sign of progress. Not only did planners hope to help people get downtown more quickly, they saw many of the neighborhoods being torn down as blighted and in need of urban renewal. But tearing down a struggling neighborhood rarely made problems like crime and overcrowding go away. To the contrary, displaced people would move to other neighborhoods, often exacerbating overcrowding problems. Crime rates rose, not fell, in the years after these projects. By cutting urban neighborhoods in half, planners undermined the blocks on either side of the freeway. The freeways made nearby neighborhoods less walkable. Reduced foot traffic made them less attractive places for stores and restaurants. And that, in turn, made them even less walkable. Those with the means to do so moved to the suburbs, accelerating the neighborhoods' decline.
Via Seth Dixon