hen Mayor Michael R. Bloomberg announced that the city was adopting a 311 hot line for public complaints, he promoted it as a way to help New Yorkers navigate the hurdle-strewn path to city services.

But in the nine months it has been active, 311 has become that and much more. In ways large and small, city officials are using information gathered through the 311 system to re-examine how city agencies carry out their jobs.

When pothole complaints started pouring into 311 after a harsh winter, Iris Weinshall, the transportation commissioner, dispatched an extra 150 workers to pothole duty, and the backlog of complaints has dropped to 975 from 3,000.

After irate residents reported problems with noise, double parking, public urination and disorderly youths over the summer, law enforcement officials used 311 technology to map out complaints by neighborhood and track down their source: illegal social clubs.

And after the 311 system made clear that more than one agency was responsible for responding to common problems — like missing manhole covers and obstructed signs — city officials assigned a primary agency to handle each kind of complaint, eliminating much of the confusion and the delays of the past.

For the first time, the 311 system is drawing together in one place all the complaints, commentary and other myriad bits of information that used to trickle in on scraps of paper and through hundreds of phone lines spread out across city agencies.

The people who run the system are then using sophisticated computer technology to analyze this trove of information provided by the public, churning out reams of data that provide statistical snapshots of city services.

In practical terms, this means that city officials can now look across the broad scope of their operations and allocate their resources more quickly and efficiently to address residents' needs and problems.

"It allows us to do more with less because we can see exactly how agencies are performing and manage our existing assets better and smarter," said Gino P. Menchini, the city's commissioner for information technology and telecommunications, who set up and runs the system. "It allows us to be able to do what we need to do without having to add additional resources. It's cost avoidance, more than anything else."

The 311 data, at the mayor's direction, is also being used much like the Police Department's highly touted Compstat system, to check up on how city agencies respond to the public every month and to hold commissioners accountable for the results.

At a recent social event, for example, Ms. Weinshall was quizzed by the mayor about how many outstanding pothole complaints she had, she said.

"You don't want to say, `I don't know,' and have him say, `Well, I know, you have 975 pothole complaints," said Ms. Weinshall, who spends several hours a month studying the data from 311. "It keeps you on your toes.' "

The 311 system operates 24 hours a day, 365 days a year, out of centers in Lower Manhattan and Long Island City. On a busy day, it handles more than 30,000 calls, helping to free up the 911 system for emergencies. Altogether, it has taken 3.69 million calls since March.

Similar systems already existed in cities like Chicago, Dallas and Baltimore, some of which are also using their call data to fine-tune city services.

In New York, each call is answered by a 311 operator, who then takes down a request or complaint, or transfers the call to someone else who can. If necessary, a caller is given a tracking number so that he or she can check back on a complaint's status.

The driving force behind it has been Mr. Bloomberg, who seems to relish using the phone line to call in potholes and illegal dumps, and then checking back to make sure they have been addressed. The number is publicized on everything from bus sides to trash baskets, and Mr. Bloomberg touts it at every opportunity — so much so that it has become a standing joke. ("Who are you going to call?")

While the overall level of customer satisfaction is still difficult to gauge, Mr. Menchini said that he kept track of comments from callers. He said people praising the service outnumbered those criticizing it by two to one.

But Betsy Gotbaum, the public advocate, said that her office has received a number of complaints from people who say they tried 311 and did not get help. She said she tried 311 herself, but hung up after being placed on hold for 35 minutes. "I think there are always kinks in a lot of systems," she said. "But I do think you need a safety net, something that's going to be a backup to that system when it falls down."

City officials, however, say that 311 has evolved into an important management tool. Just logging in the more than 7,000 services that the city provides — from repairing potholes and picking up refrigerators to issuing permits for baker's ovens — forced officials to examine how the city operates.

Even as other city departments are cutting back, the 311 system has grown from its original $21 million price tag into a $27 million-a-year operation with a staff of 375. One early effect, though, was to take much of the complaint load off individual agencies.

After the city's tough antismoking rules went into effect last spring, the health department offered free nicotine patches to any New Yorkers wishing to quit. Its hot line quickly became overloaded with calls, and the then-new 311 system kicked in to handle 30,000 more requests for the patches.

The department now uses 311 to distribute information about birth certificates, flu shots and West Nile virus, among other things, replacing dozens of other hard-to-remember phone lines.

Similarly, the 311 system has weeded out calls to the Police Department about nonpolice matters and allowed 35 communications technicians who used to staff a quality-of-life hot line to be assigned to other jobs. Police officials said that just having the system meant it could route all calls about noise and other neighborhood issues directly to local precincts. Previously, callers used to dial 911 or the quality-of-life hot line, and were not always referred to the right place.

"It is an efficiency tool, no question about it," said Police Commissioner Raymond W. Kelly. "We used to be the department of first and last resort. People would call us for just about anything, and now the calls are properly allocated."

Not everything has gone smoothly. The 311 hot lines receive between 4,500 and 4,900 calls a week from people trying to figure out how to dispose of an old refrigerator or air conditioner. For a while, the system connected them, wrongly, to the office of the sanitation commissioner, John J. Doherty. "It wasn't the worst thing in the world," said Mr. Doherty, who took down their information and passed it on. "In a relatively short time, they got the system up and running."

Mr. Menchini said setting up the database uncovered a problem with the city's day-to-day operations that had long gone unnoticed: there were overlapping jurisdictions among departments that resulted, at times, in confusion, delays and squabbling over who was responsible for fixing a particular problem.

For example, the Parks and Transportation Departments would both respond to complaints about streets signs obscured by trees. But in one of those oddities of bureaucratic logic, who would fix the problem would depend on what part of the tree was at fault. If it was the trunk, it would be transportation workers. If it was the branches, it would be a pruning issue for park workers.

Similarly, manhole covers had become another source of interagency tension. The Transportation Department repairs manhole covers that are street hazards — except in cases where they cover sewer or water lines. Then it becomes the responsibility of the Department of Environmental Protection.

"People would call, and depending on how you described it, you could call D.E.P. and they'd say `Not us,' and you could call D.O.T. and they'd say, `Not us,' " Mr. Menchini said. "So it was hit or miss, and it was always unclear, and it was an inefficient model."

Because of 311, officials said, they started a policy of designating a lead agency to respond to all calls about a specific kind of problem. In the case of manhole covers, transportation workers reported that in 90 percent of the cases, the problem was being referred to the Department of Environmental Protection, so that department was designated first responder to manhole calls.

Ms. Weinshall said that her workers made fewer wasted trips after the change, and have been able to respond more quickly to problems that they can resolve, like potholes and broken traffic lights. "It gives us the ability to focus on these issues, and not go off on wild goose chases," she said.

Meanwhile, city environmental workers have seen their workload double as they now respond to an average of 140 manhole complaints a month compared with 70 before the change. But Charles Sturcken, a department spokesman, said that the 311 system has also ended the unproductive finger-pointing that delayed such repairs in the past.

In the case of obstructed street signs, officials determined that it was most frequently a Transportation Department problem, so that is now the lead response agency.

Mr. Menchini and his staff monitor every call that comes in, compiling the data into increasingly detailed reports. These reports are sent to the mayor every two weeks, and a customized version to the major departments every month.

Each report shows how many calls were received about a particular problem or service, and how many were resolved in that month. If there is a backlog of complaints, the data also tells how long ago each complaint was made.

But 311 can do more than just record and track calls. Increasingly, its sophisticated technology is being put to use in qualitative ways. For instance, the system has taken the calls about illegal dumping and plotted them on a map to pinpoint locations where the problem seems especially persistent. Mr. Doherty said he plans to increase enforcement in those areas.

Similarly, law enforcement officers are mining the 311 data to find illegal social clubs. "It has enabled us to analyze where the quality-of-life concerns are so we're better able to address them in a pro-active way," Commissioner Kelly said.

The 311 data is also being used to set service standards for city agencies. Mr. Menchini said that each kind of service will eventually be assigned an average response time; callers can then expect to have their problems addressed within that time frame.

Some commissioners say that it is already having a profound impact.

"311 really has changed the way we do business," said Thomas R. Frieden, the health commissioner. "It's primarily not a money-saving thing, it's primarily an improvement in customer service. What it allows us to do is reach people — or allow people to reach us — much more efficiently."

Many political analysts and government oversight groups concur that 311 may be remaking city government in a fashion that is more open, and more civilized. "There's not a strong tradition in New York of city managers taking feedback from citizens," said Charles Brecher, research director for the Citizens Budget Commission. "So I think the direction is a very positive one. The real issue is how well they're implementing it."

In the meantime, 311's biggest advocate, Mr. Bloomberg, said that he was pleased with the progress so far.

"It's not just a citizen service hot line, it is the most powerful management tool ever developed for New York City government," he said. "I can't imagine running the city without it."