I've always thought that total vehicle miles are capped by the availability of gas. Since fracking has expanded that supply, at least in the short term, I'd expect those mileage charts to start upticking again.
Total vehicle miles are goverened by both oil prices and demographics. You're seeing a huge shift in demographics currently in the US, which will drive down vehicle miles.
> However gasoline prices are just part of the story. The lack of growth in miles driven over the last 7 years was probably also due to the lingering effects of the great recession (lack of wage growth), the aging of the overall population (over 55 drivers drive fewer miles) and changing driving habits of young drivers.
http://www.calculatedriskblog.com/2015/03/dot-vehicle-miles-...
> However gasoline prices are just part of the story. The lack of growth in miles driven over the last 7 years was probably also due to the lingering effects of the great recession (lack of wage growth), the aging of the overall population (over 55 drivers drive fewer miles) and changing driving habits of young drivers.