Four major subway service disruptions in the last week, including a fire yesterday that sent five people to the hospital, have highlighted a crisis in the New York subway system. Critics say the transit system is reeling from years of neglect and politican manipulation.

Three power outages crippled the overcrowded Lexington Avenue line last Wednesday. Some 750 riders of the 7 line were trapped in a smoke-filled tunnel a day later. Yesterday a fire at Atlantic Avenue and a police investigation at Columbus Circle sent commuters scrambling for alternative routes to work at the height of the morning rush hour.

While not every service disruption can be blamed on the vast decline of the system, piecemeal repairs have not addressed the overarching problems facing the Metropolitan Transportation Authority, said a senior fellow at the Manhattan Institute, a New York-based think tank.

“We’re now at the point where we have several generations of problems piled on top of each other,” Steven Malanga said. “The problem is you can never catch up. New York can only operate on a crisis basis. Once the crisis passes, the legislature exploits the system.”

Mr. Malanga points to debt, which consumes 60 cents of every dollar of revenue, pension obligations, and the sheer size of the state-run Metropolitan Transportation Authority as problems that require the active attention of the state Legislature and the governor, which jointly oversee the authority.

“There are no easy solutions,” he said, citing the fixed costs for pension and debt obligations.

Seven major subway disruptions since a fire at the Chambers Street station crippled the A and C lines for 580,000 riders eight weeks ago has brought out public fears of a return to the decrepit subways of the 1970s, said a spokeswoman for the Straphangers Campaign.

“This is the typical stuff that used to happen in the late 1970s and early 1980s until investment started,” Neysa Pranger said. “I think the bottom line is: these things are going to happen more frequently unless we invest in the sytem.”

Transportation officials fended off criticism yesterday, telling customers that things are not as bad as they seem.

“We certainly apologize. That is about all we can do for this unfortunate series of events,” a spokesman for New York City Transit, Charles Seaton, said. “What has happened in the last couple of weeks has nothing to do with funding or lack of maintenance.”

The fire on the tracks near the Atlantic Avenue subway in Brooklyn station yesterday created enough smoke that authorities suspended service for the 2/3 and 4/5 trains.

While its cause remains under investigation, officials said debris on the tracks and a spark from the third rail at 7:06 a.m. may have set the wooden railroad ties on fire. Five people were taken to Long Island College Hospital with minor injuries from smoke inhalation. Full service was restored at 8:42 a.m.

Police investigating a robbery halted subway service between 164th Street and Columbus Circle beginning at 8:05 a.m. The delay for downtown trains lasted an hour. Police said they did not catch the suspect.

For commuters north of Columbus Circle, piling onto the 1 and 9 trains, it was an unwelcome reminder of the subway fire at Chambers Street on January 23 that crippled the A and C lines for several weeks.

“I’ve lived here all my life and every other day it seems some train line is out of service,” Tonya Garcia, 27, said as she stood on the overcrowded platform of the 1/ 9 train at 137th Street. “I try to give the MTA credit where other people don’t but they are getting on my nerves actually right now. It’s a horrible inconvenience.”

Like other New Yorkers, Ms. Garcia expects crowds in a city of 8 million, but her tolerance for the disruptions is wearing thin, especially in light of the fare increases.

“I’m very tolerant but then again I haven’t purchased the new Metrocard at the higher rate,” she said. “Once I have to shell out that money for the monthly card I’ll probably get progressively more upset.”

Riders, especially those who have paid the increased fare, feel caught in a system that has become too politicized.

“It seems that no one wants to take the blame,” one commuter from Brooklyn, Jesse Levin, said. ” I’m really upset that I pay so much money for the train and it seems the MTA is not run well. I think a lot of people feel that way.”

The recent disruptions are unrelated, Mr. Seaton said, but because they follow so quickly after each other, the appearance of disrepair belies statistics that show a subway that has improved tremendously since the first capital plan was introduced in 1982.

Trains are on time 98% of the time, ridership reached a record 1.4 billion last year, and the average distance between subway car breakdowns is up from 8,000 miles in 1982 to 150,000 miles last year, he said.

“We may be victims of our own success,” Mr. Seaton said of the criticism. “As problematic as these events have been, the system is running better than it has in our entire history. Twenty years ago, events like these were nearly daily occurrences.”

But comparisons to the past mean very little to riders today, said a transportation consultant who worked for the MTA until 1998.

“The question isn’t whether it’s better than it used to be,” Bruce Schaller said. “The question is: are they meeting the needs of people using the system today.”

STRAPHANGER STRESS

A logbook of major service disruptions since the January 23 subway fire at Chambers Street.

* March 22: A subway fire of unknown origin fills the tunnels near the Atlantic Avenue station with smoke during the morning rush hour, injuring five passengers. The 2, 3, 4 and 5 lines were shut down for an hour and a half until 8:45 a.m. The Long Island Rail Road shut down service for almost an hour, stranding 3,000 commuters.

* March 22: A police investigation shuts down the A, B, C, and D trains for an hour at Columbus Circle during the morning rush hour. Thousands of riders switch to the 1 and 9 trains, overwhelming the trains and platforms. Police do not catch the suspect.

* March 17: Smoke detected in the tunnel connecting Manhattan to Queens shuts down the 7 train at 6:45 a.m., trapping 750 riders for an hour. Officials said an improperly secured metal plate became dislodged and hit the electrified third rail, creating a smoke condition.

* March 16: Three power outages shut down the Lexington Avenue line during morning and evening rush hours, wreaking havoc for about 350,000 commuters. A mysterious breach at the base of a manhole allowed brackish water to seep onto wires, causing them to short-circuit.

* February 28: Grand Central Shuttle derails after it hits a bumper, injuring three people.

* February 15: Three-alarm blaze at a Bronx apartment building disrupts rush-hour commutes for riders on the 2 and 5 trains.

* February 1: Subway fire on D line in Brooklyn disrupts service for an hour.

* January 23: A fire spreads to a control room at Chambers Street, destroying cables and wires that run the track signals. Service for the A train was disrupted and C train service was suspended until February 2, affecting 580,000 commuters daily. Officials initially misstated the service delay on the C line, estimating it would be out for five years.