Hall writes: 'Roads, on the other hand, have no impact on the extent to which development is scattered, despite commonly held beliefs to the contrary. "We looked at a lot of measures of road density - miles of road per area, average distance to a road, distance to an interstate exit - and we could find no relation between those measures and the scatteredness of development," Turner says.'
My comment: This seems to be interesting research. Of course, we already knew Los Angeles is the densest city, now it is also among the most compact (along with Miami and San Francisco). However, the measures of roads take no account of the structure of the network, or accessibility, as if transportation is simply quantifiable by the amount of pavement or distance to an exit. Imagine there were no roads, how would the city look? Perhaps roads are sufficiently pervasive that there is fundamentally no difference in the network in mature, developed US cities.
May 2006, Vol. 121, No. 2, Pages 587-633 Posted Online April 28, 2006. (doi:10.1162/qjec.2006.121.2.587) Causes of Sprawl: A Portrait from Space* by Marcy Burchfield, Neptis Foundation, Henry G. Overman, London School of Economics and CEPR, Diego Puga, University of Toronto, Universitat Pompeu Fabra, CREI, CEPR, and NBER, Matthew A. Turner, University of Toronto