CHARLOTTE, N.C. » Dan Mauney keeps misplacing his car.

Mauney, 42, lives in an apartment tower in this city’s Uptown neighborhood, a pedestrian-friendly quarter with new office buildings, sparkling museums and ambitious restaurants. He so seldom needs to drive that when he does go to retrieve his car in his building’s garage, he said, "I always forget where I parked it."

Charlotte and other American cities have not abandoned their cars or their sprawling growth. But people like Mauney are part of the reason that American driving patterns have downshifted — perhaps for years to come.

For six decades, Americans have tended to drive more every year. But in the middle of the last decade, the number of miles driven — both overall and per capita — began to drop, notes a report to be published Tuesday by U.S. PIRG, a nonprofit advocacy organization.

People tend to drive less during recessions, since fewer people are working (and commuting), and most are looking for ways to save money. But Phineas Baxandall, an author of the report and senior analyst for U.S. PIRG, said the changes preceded the recent recession and appeared to be part of a structural shift that is largely rooted in changing demographics, especially the rise of so-called millennials — today’s teens and 20-somethings. "Millennials aren’t driving cars," he said.

In fact, younger people are less likely to drive — or even to have driver’s licenses — than past generations for whom driving was a birthright and the open road a symbol of freedom. Research by Michael Sivak of the Transportation Research Institute at the University of Michigan found that young people are getting driver’s licenses in smaller numbers than previous generations.

Online life might have something to do with the change, he suggested. "A higher proportion of Internet users was associated with a lower licensure rate," he wrote in a recent study. "This finding is consistent with the hypothesis that access to virtual contact reduces the need for actual contact among young people."

Baby boomers, too, are aging out of the daily workforce and need to commute less. If the decline continues, the U.S. PIRG report states, driving could remain below its 2007 peak through 2040, even though the population is expected to grow by 21 percent.

If Jacob Curtis is any indication, the change in driving habits should be with us for some time to come. Curtis, 29, moved to Charlotte in recent months to take a job as a cameraman at a local television station, and was pleased to find a home close to rail and bus lines, and that he could ride his bike to the office along a no-traffic greenway. He can shower when he gets to work, and drives to assignments in one of the station’s vans. During his off hours, he finds Charlotte easy to navigate thanks to his smartphone, which helps him plot routes that blend biking and mass transit options. "You don’t have a lot to figure out," he said. "We all have navigators in our pockets."

Ted Boyd, whose job involves helping develop the city’s South End into a Brooklynesque neighborhood — Mauney is opening two stores there, one to sell women’s shoes and another men’s underwear — often rides the bus to work. He decided to drive less after a trip to New York, with its extensive options for mass transit, but admits "it’s a little trickier in Charlotte." Office wear still stands out on the city buses, and "you get some interesting looks sometimes," he said, that seem to assume an unpleasant reason for why he isn’t behind the wheel: "Is this a DUI?"

Charlotte, whose success as a financial center has helped its population grow toward 800,000, takes transit seriously, said David Howard, a member of the City Council and chairman of its transportation and planning committee. The city tries to channel growth into manageable areas, he said, by filling in the urban core with new development and encouraging new construction along major transportation corridors, including an expanding rail line. "It didn’t happen by mistake," he said.

The rail line was projected to reach a ridership of 12,000 people within seven to 10 years; it hit that level in the first month and a half, he said. President Barack Obama has nominated the city’s mayor, Anthony R. Foxx, to be the next transportation secretary.

The drop-off in driving is already having wide-reaching effects across the country. It means that gasoline taxes, which help finance transportation investment, are bringing in less revenue. The U.S. PIRG report suggests that the nation’s shift in driving trends calls for a change in the things the nation spends that money on. "When dollars are so scarce, we need to be sure we’re not building highways that aren’t really needed — especially if doing so means neglecting repairs of existing highways, and neglecting to build transit projects when transit ridership is soaring," Baxandall said

Kenneth Orski, a transportation consultant, offered a skeptical view of the permanence of the driving trend. "When 20-somethings get older and start having kids, they move to the more affordable suburbs in search of more space and better schools — and start driving," he said.

Robert W. Poole Jr., director of transportation policy for the Reason Foundation, a libertarian research organization, also viewed the new report with a measure of incredulity, calling its conclusions "exaggerated."

Young people have been slow to buy cars, he said, in part because of "the very large degree of youth unemployment and underemployment," a situation that might change with an improving economy. He added that the emergence of self-driving vehicles "may re-empower elderly people to continue using cars far into their last years," offsetting any potential decline from younger adults.

Arguments about the future of transportation will continue as the demographics and economics play out. But at the moment, Curtis had a more pressing problem. He was showing off his bright red Diamondback bicycle to a visitor and suddenly said, "Whoa — a flat!" A construction nail had pierced the tire, a common problem in the booming city. In an earlier time, it would have meant an irksome trip home. But not in Charlotte.

"Guess I’ll take the bus," he said.

He walked the bike to the city’s transit center, and chained it onto one of the racks that can be found on every bus in Charlotte and many other cities. The digital route readout repeated the same message over and over: "Route 9-S Central Avenue to Sav-A-Lot."