Drivers this Labor Day weekend find the cost of filling their gas tanks at a low point for the summer.

Short of celebrating with a joy ride, the decrease provides some relief for motorists burdened by high fuel prices. The regional retail gas price average is down 5 percent from mid-July and 4 percent from a year ago, according to AAA motor club.

The break is especially welcome considering that state lawmakers boosted Pennsylvania's gasoline tax by 9.5 cents per gallon in January to provide more funding for neglected bridge and highway repairs.

The decrease also reflects improved fuel efficiency, changes in driving patterns accompanying chronically high fuel costs and lingering behavioral changes from the recession of 2007, such as bundling errands and increased carpooling. Total U.S. mileage driven peaked in 2007, according to federal data.

The biggest change in driving patterns, though, comes from fewer young people taking to the road.

People in the 16- to 34-year-old age range drove 23 percent few miles on average in 2009 than in 2001, U.S. Pirg, a nonprofit advocacy group, reported last year.

Young people are more likely to live in population-dense, walkable urban areas, ride bicycles and rely on public transportation, research indicates.

The shift surfaces in a continuing decline in demand for gasoline. In June, Americans purchased an average of 354.3 million gallons of gas daily, the Department of Energy reports. It was the lowest June average since 1997, when the daily volume totaled 351.1 million gallons.