WASHINGTON — The summer vacation season began this year with Americans behind the wheel less. In all, we drove 12.2 billion fewer miles in June than a year earlier, the biggest monthly decrease in a downward trend that began in November.

That decrease, reported by the Federal Highway Administration, coincided with the national average price for unleaded gasoline hitting $4 a gallon for the first time on June 8. It peaked in mid-July at $4.11 and was down to $3.78 yesterday, according to AAA.

“Clearly, more Americans chose to stay close to home in June than in previous years,” Transportation Secretary Mary Peters said yesterday.

Overall, Americans drove 53.2 billion fewer miles from November through June than they did over the same eight-month period a year earlier, according to the highway agency’s latest monthly report on driving. That’s a larger decline than the 49.3 billion fewer miles driven by Americans over the entire decade of the 1970s, a period marked by oil embargoes and gas lines, the agency said.

A Travel Industry Association spokeswoman, Cathy Keefe, said the June driving decline “is not surprising, given the environment that we were in.” But she predicted the recent drop in gas prices to below $4 a gallon in many parts of the country will have travelers on the road again.

“I think people have started to take the increase in gas prices somewhat more in stride,” Ms. Keefe said. The trade association is anticipating only a 1.2% decline in all forms of business and leisure travel this year.

Some of the biggest declines in June, compared with a year ago, were in such popular vacation states as Maine, down 7%, and Florida, down 6%. Western states with wide-open spaces were also part of the trend — down 7.7% in Idaho, 6.9% in Utah, 6.8% in Washington, 6.7% in Nevada, 6.2% in Kansas, and 6.1% in Alaska.

The June driving data, collected by more than 4,000 automatic traffic recorders operated around-the-clock by state highway agencies, were supported by an AARP telephone survey of people age 50 and over in which 67% said they have cut back on their driving because of high gas prices.

Four in 10 said they have used public transportation, and walked or ridden a bicycle more frequently since gas prices have risen, according to the AARP poll, which was being released yesterday.

AARP’s senior vice president for livable communities, Elinor Ginzler, said she’s concerned that communities don’t have adequate sidewalks, bus shelters, bike lanes, and public transportation options as more people look for other means to get around.

“More Americans age 50-plus are trying to leave their cars behind but face obstacles as soon as they walk out the door, climb on their bikes or head for the bus,” Ms. Ginzler said.

AARP polled 1,006 people nationally between July 9 and July 15. The poll had a margin of error of plus or minus 3% points.

Gas consumption was down, too. The highway administration said motorists consumed 400 million fewer gallons of gasoline and 318 million fewer gallons of diesel in the first quarter of 2008 than in the same period in 2007.

A choir director from Rockville, Md., Rocky Twyman who has traveled to gas stations across the country leading prayers for cheaper gasoline, held a victory celebration yesterday at a Washington Shell station to thank God for lowering prices.

“So many people are being hurt by these high gas prices and it just caught America by surprise, they just weren’t ready for these adjustments that need to be made,” Mr. Twyman said.

The driving drop was not all bad, however.

“There is at least one silver lining in what’s otherwise fairly painful news and that is that less driving means less air pollution and fewer global warming emissions,” said Frank O’Donnell, of the environmental group Clean Air Watch. Emissions from cars and trucks, along with power plants, are the top sources of air pollution, he said.

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Associated Press Writer Stephanie S. Garlow in Washington contributed to this report.