MINNEAPOLIS — Americans renewed their long-standing love affair with the automobile in 2015, challenging the notion that millennials and baby boomers alike are abandoning their cars for public transit, bikes and car-sharing.

Last year, U.S. motorists drove more miles — 3.148 trillion — than any other year in history, according to data released by the Federal Highway Administration in February. And about 17 million new cars and trucks were sold in 2015, an increase of nearly 6 percent and a level of car commerce not seen since 2000.

Why?

The FHA, which logs miles driven by car, bus and truck drivers, is reluctant to speculate. “We just know there are more cars out there and they’re going farther,” said spokesman Doug Hecox.

It could be historically low gas prices.

“People may be more likely to take a road trip vs. staying at home or flying somewhere,” said Bill Holloway, a transportation policy analyst at the State Smart Transportation Initiative in Madison, Wis.

Low prices at the pump aren’t the main reason people are buying more cars; that’s likely due to a stronger economy, said Haig Stoddard, senior industry analyst for Wards Auto. But gas prices may have spurred last year’s 13 percent increase in sales of pickups, vans, sport utility vehicles and crossovers, which guzzle more fuel.

The outlook for sales remains strong, in part because so many families delayed new-car purchases during the Great Recession and its stodgy recovery.

“There are a lot of vehicles on the road that are very old, which will lead to some replacement,” Stoddard said. “You hear that vehicles built today last longer,” and people tend to keep them longer, too.

Minneapolis-area resident Ken Roberts owns two cars — a 2002 Mitsubishi with 285,000 miles, and a 2000 Chevrolet Cavalier that has clocked some 272,000 miles — and plans to drive both “into the ground.” The main criteria for a new vehicle is “four doors and good gas mileage,” he said, pointing out his 48-mile one-way commute.

Yet another long-term trend suggests the romance of the open road may be less than it seems.

In Minnesota, vehicle miles traveled, or VMT, was flat between 2004 and 2014, after decades of increases, according to Gene Hicks, director of the traffic forecast and analysis section of the state Department of Transportation. While final numbers aren’t yet available for 2015, he expects about a 3 percent increase. A 2015 MnDOT report says that even as the population has been increasing, per capita vehicle miles traveled has decreased.

Some of the decline has been attributed to millennials, the booming generation of 74 million Americans born between 1983 and 2000. A 2014 report released by the U.S. Public Interest Research Group indicates the average number of miles driven by 16- to 34-year-olds dropped by 23 percent from 2001 to 2009. This was due to young people taking fewer trips, shorter trips, and a larger share of trips by modes other than car. The fact that young people delay getting their driver’s license figures, too.

But that doesn’t mean millennials are not buying cars. Gen Yers now account for more than a quarter of all new-car sales, second only to baby boomers, according to J.D. Power & Associates.

Still, transportation analyst Doug Short of Advisor Perspectives anticipates that people young and old will continue to drive less in coming years due in part to the ubiquity of technology that enables work to be done remotely — mitigating the need to commute by car.

Short also cites a “general reversal of the flight to the suburbs,” particularly by baby boomers, which also diminishes the need to drive. “As people grow older, they drive less,” he said. “They may travel, but for a lot of people, travel doesn’t involve driving around in their car.”