Scratch that.

Calculated Risk posts that this is the fourth consecutive months with a year-over-year increase in miles driven.

The lack of growth in miles driven over the last 4+ years is probably due to a combination of factors: the great recession and the lingering effects, the high price of gasoline - and the aging of the overall population. 

I had suspected earlier that the "driving stagnation" could be attributed to structural payoffs in urbanization - i.e. people don't have to drive so much to get where they want to go. I had not thought about the impact of an aging population. Nevertheless, I don't actually think that gasoline prices are a cause. It'll be a fascinating trend to follow.