Ironically, the most fundamental question to ask about urban sprawl and transportation was in a comment thread at the Reason magazine website about a "Hit and Run" blog post regarding a Wendell Cox article:

The better question is: How many people would have chosen a suburban lifestyle if suburb dwellers had to bear the entire cost of extending transportation systems to the suburbs, and if the credit they used to finance their moves had been properly priced? How expensive would it have been to create the suburbs using private means alone? What would a price change of this magnitude have done to consumer preferences, and to the relative attractiveness of different modes of life?  Item posted by "Fluffy"  October 29, 2008, timestamped 12:21 p.m. http://reason.com/blog/show/129725.html#1125627

II suggest reading the "Hit and Run" post and the comment thread, the whole thing. It seems a lot of libertarians--or at least those reading the Reason magazine blog--strongly disagree with Randal O'Toole and Wendell Cox about their claims that land use regulations, specifically "Smart Growth", was the primary reason for the recent housing price bubble.

Hat tip to http://rationalitate.blogspot.com/ who originally spotted this quite interesting thread.