After rising for decades, total vehicle use in the U.S. -- the collective miles people drive -- peaked in August 2007. It then dropped sharply during the Great Recession and has largely plateaued since, even though the economy is recovering and the population growing. Just this week the Federal Highway Administration reported vehicle miles traveled during the first half of 2013 were down slightly, continuing the trend.
Even more telling, the average miles drivers individually rack up peaked in July 2004 at just over 900 per month, said a study by Transportation Department economists Don Pickrell and David Pace. By July of last year, that had fallen to 820 miles per month, down about 9 percent. Per capita automobile use is now back at the same levels as in the late 1990s.
Until the mid-1990s, driving levels largely tracked economic growth, according to Pickrell and Pace. Since then, the economy has grown more rapidly than auto use. Gross domestic product declined for a while during the recession but reversed course in 2009. Auto use has yet to recover.
Meanwhile, the share of people in their teens, 20s and 30s with driver's licenses has been dropping significantly, suggesting that getting a driver's license is no longer the teenage rite of passage it once was.
Researchers are divided on the reasons behind the trends. One camp says the changes are almost entirely linked to the economy. In a few years, as the economy continues to recover, driving will probably bounce back, they reason. But they acknowledge there could be long-term structural changes in the economy that would prevent a return to the levels of driving growth seen in the past.
The other camp acknowledges that economic factors are important but says the decline in driving also reflects fundamental changes in the way Americans view the automobile. For commuters stuck in traffic, getting into a car no longer correlates with fun. It's also becoming more of a headache to own a car in central cities and downright difficult to park.
"The idea that the car means freedom, I think, is over," said travel behavior analyst Nancy McGuckin.
Gone are the days of the car culture as immortalized in songs like "Hot Rod Lincoln," `'Little Deuce Coupe" and "Pink Cadillac."
"The car as a fetish of masculinity is probably over for certain age groups," McGuckin said. "I don't think young men care as much about the car they drive as they use to."
That's partly because cars have morphed into computers on wheels that few people dare tinker with, she said. "You can't open the hood and get to know it the way you used to," she said.
Lifestyles are also changing. People are doing more of their shopping online. More people are taking public transit than ever before. And biking and walking to work and for recreation are on the rise.
Social networking online may also be substituting for some trips. A study by University of Michigan transportation researcher Michael Sivak found that the decline in teens and young adults with driver's licenses in the U.S. was mirrored in other wealthy countries with a high proportion of Internet users.
Demographic changes are also a factor. The peak driving years for most people are between ages 45 and 55 when they are the height of their careers and have more money to spend, said transportation analyst Alan Pisarski, author of "Commuting in America." Now, the last of the baby boomers -- the giant cohort born between 1946 and 1964 -- are moving out of their peak driving years.
"They are still the dominant players, and they are moving toward a quieter transportation lifestyle," he said.
There's also a driving gender gap. In a role reversal, there are now more women than men in the U.S. with driver's licenses. And the declines in miles driven over the past decade were more widespread among men than women, according to Pickrell and Pace. Driving by men has declined in every age group except those 65 or older, where it increased slightly. Among women, driving declined only among young adults and teenagers.
There are several economic factors that help explain the trends. Driving declines exactly mirror job losses among men during the recession, when male-dominated industries like manufacturing and construction were especially hard hit, researchers said. But average automobile use has declined recently even among those who have remained employed.
Economists say many Americans, especially teens and young adults, are finding that buying and owning a car stretches their financial resources. The average price of a new car is $31,000, according to the industry-aligned Center for Automotive Research in Ann Arbor, Mich.
"We're not selling to everyone. We're selling to upper-middle class to upper class," said Sean McAlinden, the center's chief economist. The rest of the public, he said, buys used cars or takes the bus.
Then there's the cost of insurance, maintenance and parking. The price of gas has gone up dramatically over the past decade.
The share of younger workers who can find jobs is at an especially low ebb, while the cost of a college education -- and with it student loans -- is soaring. Many schools have stopped offering free driver's education to students. Owning a car is increasingly beyond the reach of many young drivers, researchers said.
Research by the AAA Foundation for Traffic Safety found that 18- to 20-year-olds were three times more likely to have a driver's license if they lived in a household with an annual income above $100,000 than if they lived in a household with an income below $20,000.
"I don't think it's a change in people's preferences. I think it's all economics," McAlinden said. "It might last if the economics stay the same. But if they improve, I think people will come back to driving more. ... Give a person a good job 25 miles away and they'll be at the dealership the next morning."
The decline in driving has important public policy implications. Among the potential benefits are less pollution, less dependence on foreign oil, reduced greenhouse gas emissions and fewer fatalities and injuries. But less driving also means less federal and state gas tax revenues, further reducing funds already in short supply for both highway and transit improvements. On the other hand, less driving may also mean less traffic congestion, although the impact on congestion may vary regionally.
Phineas Baxandall, senior analyst for the liberal U.S. Public Interest Research Group, says driving declines mean transportation dollars could be put to other uses.
"You just don't want to spend money you don't have for highways you don't need," he said.
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