Neighborhood Character vs. Diversity

The conventional zoning wisdom is that all structures in a neighborhood should have the same density, in order to preserve "neighborhood character."  So even in mixed-use urban areas, this sort of zoning leads to a kind of monoculture: high-rises attract high-rises, low-rises attract low-rises.

In a recent article, Vishaan Chakarbarti proposes an interesting alternative: "cap and trade" zoning.  Under this scheme, a city would "allow the free flow of air rights within an urban district, with an understanding that the overall amount of developable area would be capped in relation to proximity to mass transit."  In other worlds, instead of mandating a maximum height of 20 stories throughout a neighborhood, 50-story buildings could be balanced out by low-rises, creating a mix of densities (and perhaps of uses, to the extent that some uses are more appropriate in taller buildings).