Earlier this week, when writing about the Triangle Transit Authority’s options for spending its tax revenue, I cited a recent Randal O’Toole paper for the Cato Institute on the manifest failures of metropolitan transportation planning. There’s a section on land-use regulation worth extensive quotation:
Although transportation affects land use, University of South California planning professor Genevieve Giuliano points out that the reverse is not true: ?Land use policies appear to have little impact on travel outcomes.? This is partly because most urban facilities are already in place, so huge changes in density and design are needed to produce even small changes in mode shares or trip lengths. Few residents of Manhattan drive to work, but Manhattan is more than 20 times denser than most urban areas, and increasing the density of any urban area to Manhattan levels would be impossible.
Within the range of modern urban densities, the effects of land use on transportation are very limited. The 2000 census found that urban-area densities ranged from 850 to 7,000 people per square mile, a variation of more than 700 percent. Yet, outside the New York urban area, household auto ownership rates range from just 82 percent to 97 percent, a variation of only 18 percent. Moreover, there is little correlation between density and auto-ownership rates (correlation coefficient=0.10).
O?Toole goes on to discuss how dense land-use patterns also raise costs to consumer, not just for homes but for consumer goods (if you are expected to walk rather than drive to the grocery store, that necessarily reduces the number of stores competing for your business). As usual, insightful stuff.
