U.S. highway use was down slightly in 2011, with 1.2 percent fewer vehicle miles traveled than in 2010, and 1.3 percent fewer than in 2007.
"Gas prices are driving this," SEPTA spokesman Richard Maloney theorized. The agency's ridership increased 2.9 percent through the seven months that ended in February, and its budget for the next year anticipates an additional 2.5 percent annual increase in passengers.
"Rising employment levels and a stronger economic climate" are the primary factors, NJ Transit spokesman John Durso Jr. said, citing his agency's 5.7 percent ridership gain for the six months that ended in February.
In a national survey last month conducted by the AAA auto club, 14 percent of motorists said they were using public transportation more often because of high gas prices, and 23 percent said they would in the future if prices remained elevated.
"The question is, will they start driving again when gas prices come down?" AAA spokeswoman Jenny Robinson said.
"We think they probably will. In this country, people generally prefer to drive. It's the more convenient option: You can go from point to point when you want to without being beholden to someone else's schedule."
A key demographic in the growing use of mass transit has been young people.
Among 16- to 34-year-olds, the number of passenger miles traveled on public transit increased 40 percent from 2001 to 2009, according to the National Household Travel Survey compiled by the Federal Highway Administration. The number of auto miles traveled decreased 23 percent, the survey found.
The share of 14- to 24-year-olds without driver's licenses increased from 21 percent to 26 percent between 2000 and 2010, the agency said.
The cost of car ownership and tougher state licensing laws have likely contributed to that shift.
So have mobile phones, computers, and the boom in social media, which make it easier for young people to travel virtually, said Mantill Williams, a spokesman for the American Public Transportation Association.
"Having a car isn't necessarily the goal anymore," Williams said. "Having access to friends, sporting events, theater - that is the trend more and more."
According to the association's calculations, a Philadelphia-area commuter would save $983 a month, on average, by taking public transit to work instead of driving, because of the costs of parking, car payments, gas, insurance, and other charges.
The increased use of mass transit may affect debates in Washington, Harrisburg, and Trenton as lawmakers struggle with budgets.
In Washington, the Democratic-controlled Senate approved a long-term transportation budget that was more transit-friendly than one Republican House leaders pushed. As the sides tried to find a compromise, Congress last month passed a short-term transportation-funding bill for the ninth time since the long-term measure expired in 2009.
State legislators and governors also are wrestling with the competing demands of transit users and motorists.
In Pennsylvania, Gov. Corbett last week reiterated his opposition to any transportation-funding plan that would increase gas taxes. His transportation funding advisory commission urged in August that Pennsylvania should increase motor vehicle registration and license fees and raise a component of the gas tax to produce $2.5 billion more a year for highways, bridges, and mass transit. The Republican governor says the state can't afford it.
In New Jersey, Gov. Christie last week came under renewed fire from transit advocates for canceling a rail tunnel between New York and New Jersey that would have doubled the maximum number of rush-hour trains available to commuters.
When he canceled the project in 2010, Christie said it was too costly. He shifted the state's portion of the tunnel money to the Transportation Trust Fund, the main source of money for highway and mass-transit projects.
Policy-makers should change how they evaluate transportation funding, a liberal think tank said in a report this month.
"America has long created transportation policy under the assumption that driving will continue to increase at a rapid and steady rate," the U.S. Public Interest Research Group said. "The changing transportation preferences of young people - and Americans overall - throw that assumption into doubt."
Contact Paul Nussbaum at 215-854-4587 or firstname.lastname@example.org.