The automotive industry is getting more evidence that it's time to expand product offerings or switch over to another business. A new study by the US Public Interest Research Group (PIRG) says the "driving boom" is over. While Baby Boomers loved their cars, their kids - aka Gen Y or Millennials - have different idea.

From 2004 until 2012, the total miles traveled remained about the same, but the amount, per capita, decreased by one percent each year.

The numbers tell the story, and the total miles driven, per capita, in the US has been declining. While gasoline price spikes and the Great Recession play a role, the numbers have been dropping gradually since 2004. That marks the end of a 40-year driving boom that started up in 1964, according to the PIRG report. The number of miles driven by Americans increased each year an average of 2.5 percent per capita and 3.8 percent total during that time. From 2004 until 2012, the total miles traveled remained about the same, but the amount, per capita, decreased by one percent each year.

Urbanization appears to be causing some of the trend, and use of mass transit and carsharing has been increasing. On top of that, boomers are aging and will be driving less and Millenials don't like to drive as much. Automaker executives have been voicing concern that young people are much less interested in driving and owning cars then their predecessors. The PIRG report's authors are concerned that highway system authorities have been too focused on expanding the nation's roads rather than accurately gauging the landscape.