It appeared to be the season that the New York City subway would finally rebound from the coronavirus pandemic.

Crime rates were declining in the transit system. Ridership was up, climbing from the lows reached during the worst of the health crisis. And the Metropolitan Transportation Authority, which runs the transit network, had recently received an infusion of funding from the state that prevented a fiscal crisis. The signs pointed to a hopeful trajectory.

A violent attack now threatens to disrupt that optimism.

On Wednesday, a man at the Fifth Avenue-53rd Street subway station whom the police described as emotionally disturbed shoved a 30-year-old woman against a departing train. After striking her head on a subway car, she fell onto the tracks. As of Thursday, the woman, whose name has not been released, remained in critical condition.

The police have arrested Sabir Jones, 39, as a suspect in the attack. Michael Kemper, the Police Department’s chief of transit, said Mr. Jones was “known to the department” through a previous arrest and by his constant presence in subway stations. Mr. Jones was picked up on Thursday near the PATH train stop at Newark Penn Station. He remained in custody on Friday.

Familiar questions about the safety of the transit system have resurfaced. The attack has also renewed calls for the authority to install additional protective features like platform barriers that could help keep transit riders from falling onto the tracks.

Assemblyman Alex Bores, whose district includes the subway station where the pushing occurred on Wednesday, said he was frustrated by the M.T.A.’s slow pace in installing barriers, like waist-high metal gates.

“We need to get ridership back up to where it was prepandemic,” Mr. Bores said. “There’s many things we can do to increase it. Among those is safety and the perception of safety, and I think fixed barriers go a long way.”

In a subway system used by roughly four million riders on an average weekday, being shoved onto tracks is rare. This year through Oct. 15, there had been 15 people pushed off subway platforms in New York City, compared with 22 during the same period last year, the police said. Officials could not say how many of the episodes resulted in serious injuries but said that many of those who were shoved were able to emerge safely.

Leaders at the M.T.A. are sensitive not only to crime rates in the system, but also to how safe riders feel. Even though violent attacks in the system are relatively uncommon, the idea of being pushed onto train tracks is a powerful fear for many riders.

The authority has long been under pressure to block access to tracks by building screen doors similar to those that have been installed in other major transit systems in Paris, London and Hong Kong. Transit leaders had resisted calls to do so, citing “special complexities” in retrofitting New York’s century-old system. The authority reversed course in February 2022, about a month after Michelle Alyssa Go, a 40-year-old worker at the consulting firm Deloitte, was shoved to her death in front of a train at the Times Square subway station.

A small pilot program announced last year promised to install screen doors at a handful of stations. Transit leaders have said that the work is not expected to be completed before next year.

On Friday, an M.T.A. spokesman said that the authority is seeking a contractor to build the pilot program’s screen doors, whose $100 million price will be paid for by money generated from a congestion pricing toll program that is being finalized and is expected to generate $1 billion annually. In other transit systems around the world, the screen doors block the track area from platforms until trains arrive.

Transit leaders have said that New York’s system poses many challenges in adding the safety feature, with some subway platforms that are too narrow or that can’t bear the extra weight. The subway also uses different train car models that can’t be easily aligned with barriers.

A February 2020 study commissioned by the authority determined that only 128 of the system’s 472 stations could fit the barriers within the next decade because of cost and engineering concerns. The authority estimated that outfitting those stations could cost $7 billion, plus annual maintenance expenses of roughly $119 million.

Michiko Ueda-Ballmer, an associate professor at Syracuse University who has studied the efficacy of platform barriers in preventing people from getting on railway tracks in Japan, said the authority should install at least small metal gates to make the system safer.

“It’s better than nothing,” Ms. Ueda said. “If there’s somebody pushed, just by accident, and if you have metal bars, I think that would definitely help.”

The subway system is considered a lifeblood of the city, and the M.T.A. is under intense pressure to bring back riders who virtually abandoned mass transit at the height of the pandemic.

Restoring their confidence is key to New York’s economic recovery, and the state has mandated that the authority improve service as part of a budget deal that saved it this year from financial decay. Ridership currently hovers at about 70 percent of prepandemic levels on weekdays.

On Wednesday, Studi Shah, 27, who was visiting from Gujarat, India, was among dozens of pedestrians turned away by police officers from the Fifth Avenue-53rd Street station where the shoving occurred. Ms. Shah said the incident made her afraid to use the subway.

“It is literally scary,” Ms. Shah said.

Chief Kemper has described Mr. Jones as being homeless. State and city officials have ramped up efforts during the past two years to relocate homeless people who shelter in the subways and train stations, sometimes doing so forcibly. City officials said that as of September, they had assisted 5,478 people in finding shelter as part of that plan.

Officials have also flooded the system with police officers during that time to soothe rider fears. In recent weeks, they have instructed officers who would normally be undercover to wear their uniform in hopes of easing public anxiety over the conflict in Israel.

From January through September, major felonies in the subway system were down by 5 percent compared with the same time period last year, according to police statistics.

In September, the police counted 175 major felonies in the transit system and the M.T.A. logged about 95 million rides, putting the rate of violent crimes at about 1.8 per one million rides.

By comparison, the Southeastern Pennsylvania Transportation Authority, which serves Philadelphia and the surrounding area, had a felony rate of 1.6 crimes per one million rides in September.

On Wednesday, Janno Lieber, the transportation authority’s chair and chief executive, said progress had been made on subway crime, but he urged public officials to do more to help homeless people in crisis.

“We need for them to get in treatment and out of the public space,” Mr. Lieber said. “When things like this happen, we have to double down and work even harder to protect New Yorkers.”

Asmaa Elkeurti contributed reporting.