More frequent buses. Late-night trains. Better weekend service.

That's what SEPTA promises in the next few weeks and months as it launches what it calls its most ambitious service expansion ever.

After decades of cuts, SEPTA will announce today a $10 million project aimed at easing overcrowding and improving daily service. The first of the 65 upgrades will begin Aug. 25, and all of the changes are to be made by Nov. 3.

The changes will include bigger buses on busy Route 14 along Roosevelt Boulevard between Northeast Philadelphia and Bucks County, more frequent service on Route 23 between Chestnut Hill and South Philadelphia, and after-midnight trains on the R5 Paoli/Thorndale, R6 Norristown, and R7 Trenton Regional Rail lines.

"This is really unprecedented for us," SEPTA general manager Joseph Casey said. "We need to respond to increased ridership and other customer needs."

With commuters reacting to higher gasoline prices and switching from cars to public transit, SEPTA's ridership has increased by about 6 percent, or 38,000 trips a day, from a year ago. Rail ridership is up 12 percent, to its highest point in 25 years, and many rush-hour trains are packed with standing passengers.

"It's been getting pretty crowded" on his daily commute, Rico Paolino of Horsham said yesterday as he waited for an R5 train at Suburban Station. When he catches his usual 6:30 a.m. train in Ambler, "you may not get a seat."

Now, at the height of summer-vacation season, crowding isn't too bad, he said. "But the first week everybody's back in school, it will really be packed."

Casey, who became general manager early this year, credited the state's new transportation-funding law, Act 44, with providing the money to make the improvements possible. He said more expansion might be on the way, as SEPTA tries to hang onto its new riders and attract more.

To handle the expanded service, SEPTA is hiring 184 bus and train operators, mechanics, cleaners, police officers, maintenance workers, and customer-service agents.

The new bus service is made possible by the arrival of the first 40 of more than 400 hybrid diesel-electric buses to be delivered over the next four years.

New rail cars also have been ordered, but the first of the 120 Silverliner V cars are not likely to be in service until 2010. In the meantime, eight used rail cars bought from NJ Transit will be added to SEPTA's fleet by October to help ease overcrowding.

SEPTA will tout its improved service with a $1 million advertising campaign on TV, newspapers and radio, and it will pitch its late-night service to college students with whimsical ads on bar coasters, coffee-cup sleeves, and Internet banners.

The chance to add service is a big change for SEPTA after decades of route cutbacks, "doomsday scenarios," and higher fares. After lowering riders' expectations for years, SEPTA officials acknowledged the challenges they face in offering more to passengers.

"Certainly, there is a risk," said Pat Nowakowski, assistant general manager for operations. "We will create expectations, and we have to work to make sure we meet them."

Kim Scott Heinle, assistant general manager for customer service, said, "We don't want to invite people to a party and then have a bad time." Heinle said his staff would work to make sure details such as signs and rider information make the new service easy for passengers to use.

Of the 65 route changes, 26 are designed to reduce overcrowding on SEPTA buses. Nine upgrades involve adding peak-hour trips to improve service, such as the addition of 14 round trips on Route 201 in Fort Washington. And 30 of the changes are designed to improve midday, evening, weekend and late-night service for buses and trains, such as the addition of a 1:32 a.m. train from Trenton to give Friday-night passengers out of New York a later connection.

"We're no longer a 9-to-5 society," said Charles Webb, chief planning officer for SEPTA. He said the later trains "are a test of this market. We've received a lot of requests for later service."

At Suburban Station, Regional Rail riders said any changes to reduce overcrowding would be welcome. But peak-hour commuters said they wouldn't see much benefit from the new late-night service.

"Sometimes we stay in Center City for the theater and dinner, and late trains might help then," Paolino said. "We might not feel so rushed."

Stephanie Hartman, 26, of Somerton, said she would rather see SEPTA add earlier trains.

"When I have to go to the airport early, there aren't any trains running. Even 5 a.m. would be better."

And she bemoaned infrequent midday service: "There's only one train an hour."

Bus riders said more frequent service and less-crowded buses would be a good thing. Regular passengers said that they had noticed the increase in ridership and that, in some cases, SEPTA's actions had made things worse.

On Route 27, from Center City to Roxborough, passengers have noticed that large 60-foot "articulated" buses, which can hold up to 100 riders, have been replaced with standard 40-foot buses, which can accommodate 60. SEPTA says it is shifting articulated buses from Route 27 to Route 14 to ease overcrowding there.

"It's even more crowded now," said Nicole Green, 18, waiting for a bus to take her home to Roxborough from her summer job at a Rita's Water Ice stand at 15th and Market Streets. "I don't understand that."

From a rider's perspective, SEPTA's expansion plan "is all good. . . . The only thing I'd like to see is things they can't do because they don't have the equipment," said Bob Clearfield, chairman of the Citizen Advisory Committee, a passengers' advocacy panel that advises SEPTA.

"I'd like to see more trains or more train capacity, but they're making maximum use of the equipment they have," Clearfield said.