The Department of Transportation’s Federal Highway Commission has released the latest report on Traffic Volume Trends, data through April. Travel on all roads and streets declined by 0.4% (-1.0 billion vehicle miles) for April 2012 as compared with April 2011. The 12-month moving average of miles driven declined by 0.7% from April a year ago.
Total Miles Driven, however, is one of those metrics that must be adjusted for population growth to provide the most revealing analysis, especially if we’re trying to understand the historical context. We can do a quick adjustment of the data using an appropriate population group as the deflator. I use the Bureau of Labor Statistics’ Civilian Noninstitutional Population Age 16 and Over (FRED seriesCNP16OV). The next chart incorporates that adjustment with the growth shown on the vertical axis as the percent change from 1971.