When density rises, vehicle miles decrease
An analysis of 11 Midwestern metro areas suggests that when population density is increased by 10 percent, household vehicle travel and emissions decline by 3.5 percent. “We found compactness to be associated with greater reductions in vehicle travel than in previous studies,” write Brian Stone Jr., Adam C. Mednick, Tracey Holloway, and Scott N. Spak in an article in the Autumn 2007 Journal of the American Planning Association.
In “Is Compact Growth Good for Development?” the authors estimate what the results would be if the Midwestern urban areas adopted the compact-growth strategy used by metropolitan Portland, Oregon. Where the higher density occurs makes a big difference in terms of reducing vehicle miles traveled (VMT). Increasing density in urban zones is more than twice as effective at reducing VMT and emissions than is increasing density in suburban areas.