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Take a look at this Google Maps satellite map of Camden, New Jersey's downtown. It is an example for every misguided "urban renewal" plan hatched in the last 60 years.
The best place to start is the rabbit-shaped spot right in the middle. It's dedicated to parking for downtown Camden, for the Stadium and Aquarium on the waterfront and for people commuting to Philadelphia across the river. Forget about carbon emissions or fuel consumption, the amount of space cars will take up if you let them is enormous. Not just do they need roads, they need places to be parked at home, at work and anywhere else you might venture. As a result, a lot of whatever used to be in that huge gray mass, for whatever reason, is blacktop.
Next, we have the two parts of Camden out of the main lump that aren't parking. They're Campbell Field and the Adventure Aquarium. Both were built at huge taxpayer expense, both were "downtown" improvements and both failed miserably at bringing any development in a deeply troubled but geographically fortunate city. Think how that money could have been spent in the most dangerous city in America. The only problem is that you can raise money in the capitol to build a stadium, but the state won't help out to pay for a lot of the basic stuff that makes cities livable. Oh, and you'll need tons of parking for the suburbanites to park to see the attractions.
Third, there's the small matter of the highway streaking across town. From the old I-93 in Boston to the Cross Bronx in New York, interstates tear neighborhoods apart and choke off entire sections of town from pedestrian traffic. Crime-wise, no pedestrians mean few witnesses to street crime. Fewer witnesses mean more witness intimidation and lower conviction rates.
The residents of Camden to the north of 676 have to go under the highway or even around the toll booths to get to the PATCO train or the university. The obvious neighborhood to target for redevelopment (at least geographically) is cut off from the two places in town they might want to go.
What now? You can't well tear down the highway to the main bridge to Philadelphia, but some work could be done on that parking. There could be more multi-level facilities built (I see some already) or better yet more use of public transit to reduce dependence on parking.
Yet just like Baltimore, there are any number of other factors at play. A tax base is probably a prerequisite to solving any number of urban maladies, but the pathologies of life in a post-industrial secondary city won't be fixed by more pedestrian walkways and a couple of brewpubs.