The '57 Chevy was still a year away when the launch of the interstate highway system kicked U.S. car culture into high gear. But six decades later, changing habits and attitudes suggest America's romance with the road may be fading.

After rising almost continuously since World War II, driving by U.S. households has declined nearly 10 percent since 2004, with a start before the Great Recession suggesting economics is not the only cause. "There's something more fundamental going on," says Michael Sivak of the University of Michigan Transportation Research Institute.

The average American household now owns fewer than two cars, returning to the levels of the early 1990s.

More teens and 20-somethings are waiting to get a license. Less than 70 percent of 19-year-olds now have one, down from 87 percent two decades ago.

"I wonder if they've decided that there's another, better way to be free and to be mobile," says Cotten Seiler, author of "Republic of Drivers: A Cultural History of Automobility in America."

Those changes — whether its car trips replaced by shopping online or traffic jams that have turned drives into a chore — pose complicated questions and choices.

TRYING ALTERNATIVES: Each day, about 3,500 people bike the Midtown Greenway, a freight rail bed converted to cycle highway in Minneapolis, where two-wheel commuting has doubled since 2000. It's still a small percentage, but more residents are testing the idea of leaving cars behind.

A second light rail line opens in June. Street corners sprout racks of blue-and-green shared bikes. About 45 percent of those who work downtown commute by means other than a car, mostly by express bus. That syncs with figures showing Americans took a record 10.7 billion trips on mass transit last year, up 37 percent since 1995.