One indicator of sprawl: New housing goes up faster than new households.
"In Providence, Newark and Ann Arbor, new housing goes up every day as more and more families move into the region," notes an article in the Buffalo News. "Buffalo also builds a lot of new housing, but with a difference: Here, the number of new houses outpaces the number of new households by nearly 4-to-1. ...
"[r]esearchers believe the impact of that sprawl hit hardest in Buffalo and its first-ring suburbs. They see it in the exodus of people from the city and the decline in both property values and tax base."
Declining housing prices is certainly NOT a problem we've got here in the Boston area at the moment. But it's worth keeping in mind that exurban sprawl (i.e. in the 495 region and beyond) impacts both a region's major city AND its closer-in suburbs. When once-rural town build nothing but developments of large houses, without enough commercial activity to support it, where do you think all that traffic goes when people need to get to work or go shopping?