DENVER — With the price of gas approaching $4 a gallon, more commuters are abandoning their cars and taking the train or bus instead.
Mass transit systems around the country are seeing standing-room-only crowds on bus lines where seats were once easy to come by. Parking lots at many bus and light rail stations are suddenly overflowing, with commuters in some towns risking a ticket or tow by parking on nearby grassy areas and in vacant lots.
“In almost every transit system I talk to, we’re seeing very high rates of growth the last few months,” said William W. Millar, president of the American Public Transportation Association.
“It’s very clear that a significant portion of the increase in transit use is directly caused by people who are looking for alternatives to paying $3.50 a gallon for gas.”
Some cities with long-established public transit systems, like New York and Boston, have seen increases in ridership of 5 percent or more so far this year. But the biggest surges — of 10 to 15 percent or more over last year — are occurring in many metropolitan areas in the South and West where the driving culture is strongest and bus and rail lines are more limited.
Here in Denver, for example, ridership was up 8 percent in the first three months of the year compared with last year, despite a fare increase in January and a slowing economy, which usually means fewer commuters. Several routes on the system have reached capacity, particularly at rush hour, for the first time.
“We are at a tipping point,” said Clarence W. Marsella, chief executive of the Denver Regional Transportation District, referring to gasoline prices.
Transit systems in metropolitan areas like Minneapolis, Seattle, Dallas-Fort Worth and San Francisco reported similar jumps. In cities like Houston, Nashville, Salt Lake City, and Charlotte, N.C., commuters in growing numbers are taking advantage of new bus and train lines built or expanded in the last few years. The American Public Transportation Association reports that localities with fewer than 100,000 people have also experienced large increases in bus ridership.
In New York, the Metropolitan Transportation Authority reports that ridership was up the first three months of the year by more than 5 percent on the Long Island Rail Road and the Metro-North Railroad, while M.T.A. bus ridership was up 10.9 percent. New York City subway use was up 6.8 percent for January and February. Ridership on New Jersey Transit trains was up more than 5 percent for the first three months of the year.
The increase in transit use coincides with other signs that American motorists are beginning to change their driving habits, including buying smaller vehicles. The Energy Department recently predicted that Americans would consume slightly less gasoline this year than last — for the first yearly decline since 1991.
Oil prices broke yet another record on Friday, climbing $2.27, to $125.96 a barrel. The national average for regular unleaded gasoline reached $3.67 a gallon, up from $3.04 a year ago, according to AAA.
But meeting the greater demand for mass transit is proving difficult. The cost of fuel and power for public transportation is about three times that of four years ago, and the slowing economy means local sales tax receipts are down, so there is less money available for transit services. Higher steel prices are making planned expansions more expensive.
Typically, mass transit systems rely on fares to cover about a third of their costs, so they depend on sales taxes and other government funding. Few states use gas tax revenue for mass transit.
In Denver, transportation officials expected to pay $2.62 a gallon for diesel this year, but they are now paying $3.20. Every penny increase costs the Denver Regional Transportation District an extra $100,000 a year. And it is bracing for a $19 million shortfall in sales taxes this year from original projections.
“I’d like to put more buses on the street,” Mr. Marsella said. “I can’t expand service as much as I’d like to.”
Average annual growth from sales tax revenue for the Bay Area Rapid Transit District, a rail service that connects San Francisco with Oakland, has been 4.5 percent over the last 15 years. It expects that to fall to 2 percent this year, and electricity costs are rising.
“This is a year of abundant caution and concern,” said Dorothy W. Dugger, BART’s general manager, even though ridership on the line was up nearly 5 percent in the first quarter of the year.
Nevertheless, Ms. Dugger is happy that mass transit is winning over converts. “The future of mass transit in this country has never been brighter,” she said.
Other factors may be driving people to mass transit, too. Wireless computers turn travel time into productive work time, and more companies are offering workers subsidies to take buses or trains. Traffic congestion is getting worse in many cities, and parking more expensive.
Michael Brewer, an accountant who had always driven the 36-mile trip to downtown Houston from the suburb of West Belford, said he had been thinking about switching to the bus for the last two years. The final straw came when he put $100 of gas into his Pontiac over four days a couple of weeks ago.
“Finally I was ready to trade my independence for the savings,” he said while waiting for a bus.
Brayden Portillo, a freshman at the University of Colorado Denver, drove from his home in the northern suburbs to the downtown campus in his Jeep Cherokee the entire first semester of the school year, enjoying the rap and disco music blasting from his CD player.
He switched to the bus this semester because he was spending $40 a week on gas — half his salary as a part-time store clerk. “Finally, I thought this is stupid,” he said, and he is using the savings to pay down a credit card debt.
The sudden jump in ridership comes after several years of steady, gradual growth. Americans took 10.3 billion trips on public transportation last year, up 2.1 percent from 2006. Transit managers are predicting growth of 5 percent or more this year, the largest increase in at least a decade.
“If we are in a recession or economic downturn, we should be seeing a stagnation or decrease in ridership, but we are not,” said Daniel Grabauskas, general manager of the Massachusetts Bay Transportation Authority, which serves the Boston area. “Fuel prices are without question the single most important factor that is driving people to public transportation.”
Some cities are seeing spectacular gains. The Charlotte Area Transit System, which has a new light rail line, reported that it logged more than two million trips in February, up more than 34 percent from February 2007.
Caltrain, the commuter rail line that serves the San Francisco Peninsula and the Santa Clara Valley, set a record for average weekday ridership in February of 36,993, a 9.3 increase from 2007, according to its most recent public calculation.
The South Florida Regional Transportation Authority, which operates a commuter rail system from Miami to Fort Lauderdale and West Palm Beach, posted a rise of more than 20 percent in rider numbers this March and April as monthly ridership climbed to 350,000.
“Nobody believed that people would actually give up their cars to ride public transportation,” said Joseph J. Giulietti, executive director of the authority. “But in the last year, and last several months in particular, we have seen exactly that.”