The Department of Transportation's Federal Highway Commission has released the latest report on Traffic Volume Trends, data through June. Travel on all roads and streets changed by 0.4% (1.1 billion vehicle miles) for June 2012 as compared with June 2011. However, the 12-month moving average of miles driven declined by 0.2% from June a year ago (PDF report). And the total population-adjusted data likewise has set a new post-crisis trough.
Here is a chart that illustrates this data series from its inception in 1970. I'm plotting the "Moving 12-Month Total on ALL Roads," as the DOT terms it. See Figure 1 in the PDF report, which charts the data from 1987. My start date is 1971 because I'm incorporating all the available data from the DOT spreadsheets.