In Atlantic Cities, Chris McCahill and Norman Garrick report a negative relationship between population and job growth (living, working), and driving within the city. This they attribute to a simple mechanism: cars (and, in particular, parking spaces) displace people. Note in particular the that the cities with declining median income, and people (jobs & residents), saw big increases in parking space & driving. The sample is small, but the story is plausible. Maybe Detroit really does need more parking!