The total number of vehicle miles traveled in the US used to largely do only one thing: go up. This is made it fairly easy for the Federal Highway Administration (FWHA) to forecast how much more Americans were going to drive in the coming years – they just extended the trend line.
Below is what that looked like since the early 1970s (via FRED Economic Data). You’ll see that the total vehicle miles traveled went from somewhere around 1.1 trillion miles to around 3 trillion miles in and around the late 2000s. The shaded areas represent recessionary periods.
But then in 2007, something happened. Total vehicle miles traveled peaked, declined, and then flat lined at just under 3 trillion miles. Here’s what that looked like (the ending time period is October 2014):
However, since this was new for the FHWA, they continued to believe that this would ultimately correct itself and that total VMTs would eventually continue on their linear ascent. So here’s what their projections looked like (via State Smart Transportation Initiative):