PORTLAND — You may not believe this if you're a regular victim of rush-hour gridlock. But Oregonians are driving less.

PORTLAND — You may not believe this if you're a regular victim of rush-hour gridlock. But Oregonians are driving less.

At its 2004 peak, the average distance traveled per person per year in Oregon was 9,936 miles, according to analysis of traffic data by The Oregonian newspaper. The number dropped to 8,836 miles during the 2008 recession and has continued to fall — to 8,548 in 2012 — despite the improving economy.

The figures reflect a national trend that researchers call "driving light." Motorists are often getting behind the wheel only when they must, such as getting to and from jobs at the same time as everybody else, hence the bottlenecks.

"They're certainly not becoming anti-car," said Jackie Douglas, executive director of the Boston-based alternative-transportation advocacy group LivableStreets Alliance. "But with the cost of driving, along with tightening budgets and changing attitudes, more households are realizing they don't need to drive everywhere and they don't need a car for every family member who can drive."

Other numbers show the trend may continue. Ten years ago, 85 percent of 16-to-21-year-old Oregonians were licensed to drive. Today, it's 71 percent. Meanwhile, passenger vehicle ownership has increased by only 4 percent in the past decade, even as Oregon's driving-age population jumped by 14 percent, Oregon Driver and Motor Vehicle and U.S. Census statistics show.

In a few areas, vehicle registration has grown with the population. Since 2002, for example, the number of Washington County residents has increased 16 percent to 547,672 and the number of registered passenger vehicles is up 14 percent to 418,265, suggesting that development patterns, industrial expansion and TriMet cuts in the fast-growing Portland suburbs have left them as car-dependent as ever.

But in Multnomah County, where Portlanders are increasingly sharing cars, riding bikes and taking mass transit, the number of registered vehicles grew by less than 1 percent, even as the population jumped by 11 percent.

Pablo Hernandez, 32, of Portland, works as a program manager at Yahoo in Hillsboro, and owns one of the 515,991 vehicles registered to residents of the state's largest county. Two years ago, Hernandez and his partner owned two cars.

But he said the cost of insurance, gas and maintenance forced them to reluctantly sell one. It helped that his office is near a light-rail station and car-sharing companies such as Zipcar and Car2Go picked Portland as one of their start-up markets.

"Car2Go is my second car when I need it," he said.

A University of Michigan study published this summer also showed driving hitting a peak in 2004. The study's author, Michael Sivak, noted four key reasons for the decline: a migration to urban centers with public transit, baby boomers driving less as they age, the telecommuting boom and the drop in the percentage of teenagers getting their driver's licenses.

"The long-held belief is that the Great Recession hit and forced people to cut back on their driving," Sivak said. "But it's clear that something else was happening with society before that."