The authority’s interim executive director, Veronique Hakim, argued that the subway system was more reliable than critics claimed, but she said officials were working to bring down delays. The agency is deploying staffers at busy stations to direct traffic; ordering open-end subway cars with accordionlike connectors instead of doors at the ends of cars, opening up more space; and improving signals to run more trains, she said.

“There is not one single panacea that’s going to solve this,” Ms. Hakim said in an interview. “This is about tackling many fronts.”

Ms. Hakim said the reliability of trains, known as mean distance between failure, had dropped because it had reached an artificially high level when a large order of new subway cars arrived in 2010. The figures will improve, she said, when a batch of new cars begins to arrive this year.

“We haven’t cut back on maintenance,” Ms. Hakim said. “We’re dealing with an aging fleet.”

New York’s subway is also one of the few systems in the world that run 24 hours a day, adding to wear and tear and leaving few windows for workers to perform maintenance on the tracks.

Despite their deteriorating performance, subway cars are far more reliable than they were in the 1980s, when the system was plagued by financial shortfalls that crippled service; in 1981, trains broke down every 6,000 miles. But David L. Gunn, a former subway leader who helped turn around the system in the 1980s, said even older cars could perform well if properly maintained.

“If you do the scheduled overhaul of a car fleet on a regular basis, you shouldn’t get a rapid decline in the reliability,” Mr. Gunn said.