Tia Corry, an 18-year-old server at Uno Chicago Grill in Largo, was accustomed to Metrorail getting her to work in 45 minutes, but yesterday morning, she was late, forced to take a shuttle bus through rain and heavy traffic because a stretch of her line had been shut down for maintenance.

"I'm upset," she said. She had already called her boss, but she said she could count the tips she was going to miss.

Such irritation and inconvenience have been the rule on weekends recently as repairs and equipment replacement on Metro have caught many riders by surprise.

Maintenance is often done on weekends when ridership is lower and fewer people would be inconvenienced, but that, in turn, has irked Washington area residents who conscientiously use Metro on weekends because Metro and local officials have urged them to.

"It is getting ridiculous where nearly every weekend there is extensive track work done, especially where there are activities going on where people are encouraged to take Metro," said Sara Krauss, whose trip to Rockville for dinner with friends last Saturday took twice as long as usual.

This weekend, Metro officials closed four Orange and Blue Line stations and ran connecting shuttle buses while they installed new shock-absorbent padding under rails on the bridge of the Anacostia River.

The maintenance work this weekend and last was extensive, Metro officials said, and required more than the odd day or a few early morning hours to complete.

"Track work is absolutely critical to keeping a system reliable and safe," Metro spokeswoman Leona Agouridis said. "We try to do the track work at night . . . but there are certain things that are major projects and cannot be done in intervals."

The Anacostia bridge work was announced several days ago, but plenty of people did not get the word.

At the Cheverly Station on the Orange Line in Maryland, several riders looked up in astonishment when the car they expected to take them into the District instead started back toward New Carrollton. "They told us those stations ahead were closed, but they didn't tell us they were going to turn this train around," one man said.

He was supposed to have gotten off the train at Cheverly and taken a free shuttle bus to the Stadium-Armory Station, where his Metrorail journey could resume. But he said the announcements on the train were inaudible or did not say that.

Rain yesterday kept ridership light. Many of the travelers affected by the delays were heading into the District for sightseeing and said they were not worried about missing appointments.

Chris Pajak, who lives in Chester, Md., was taking his wife, two children, sister, nephew, father and mother to see the National World War II Memorial. His father, Theodore, a World War II veteran, was celebrating his 84th birthday, and everyone was looking forward to sightseeing and a good lunch. It wasn't until the third announcement on the train that Pajak realized his large group was going to have to get out and ride the shuttle bus, "just a little bit of an inconvenience," he said.

Shorter delays are expected today on the Green Line. The Blue and Orange lines should be running as usual by this morning, Metro officials said.

Several veteran Metro riders said they had given themselves extra time, because bad things sometimes happen. Rob Oates, a student at the University of Maryland, left an hour earlier than necessary for his interview for a part-time job with Metro Transit Police and just made it on time. WOL radio talk show host Truth Hall headed to work four hours early. He said he still preferred Metro to the dingy and ancient New York subway.

Tyrone Brown, one of the shuttle bus drivers, said riders were mostly patient. Mary McCrae, another driver, let some people off at personal stops, rather than making them wait to get off at the next Metro station.

It could have been worse, said Scott Hertzberg, a librarian and farmer from Upper Marlboro. He had just dropped off his wife at an Amtrak station, where the trains were running two hours late. He was headed for some museums and said the delays would not bother him.

"It's Saturday," he said. "No great rush."

A shuttle at the Stadium-Armory Station picks up riders to ferry to the next open station as track work is completed.