I worked for a car parts reseller that said, in their quarterly meetings we were forced to attend, the 'miles driven' indicator was the main predictor for their business. It had started going sideways by the time I joined the company, but they were optimistic about it turning up soon and reaching new highs like it used to effortlessly do.
Here's an article with some interesting analysis by a financial guru type. He adds in the population deflator and recalculates the indicator. Curiously enough, when adjusted for population it PEAKED IN 2005!! Here's the link:
http://www.advisorperspectives.com/dshort/updates/DOT-Miles-Driven.php
Lots of cool graphs in the article, but as gifs, they don't want to post for me here.