Businesses in New York City will be asked to change workers’ schedules to reduce rush-hour density on the subway. A new squad of guards will patrol stations, reporting overcrowding to supervisors and directing riders to emptier train cars. Brightly colored markers will be added to encourage riders to keep a distance from one another on platforms, following the advice of transit agencies in China, Singapore and Britain.
New York’s transit agency took the drastic step on Thursday of halting overnight service on the system for the foreseeable future to give workers more time to disinfect trains and stations.
But it is just a first step for officials racing to develop a strategy for ensuring that the subway can rebound from a cataclysmic pandemic.
As authorities weigh decisions about when to begin letting some businesses reopen, New York’s ability to revive its economy hinges on whether millions of daily commuters will return to a public transit network that they are persuaded can provide safe and reliable service.
But it remains an open question whether it will be even possible for riders to practice social distancing on a system whose core purpose is to carry throngs of people in confined spaces.
The challenge is testing the Metropolitan Transportation Authority, the largest transit agency in the United States, as it reels from an outbreak that has drained the subway of more than 90 percent of its riders, killed nearly 100 workers and sickened thousands more and led to the largest financial crisis in authority history.
“If we are going to have a real economic recovery, we have to solve the question of making public transit safe and making sure people feel safe,” said Nick Sifuentes, the executive director of Tri-State Transportation Campaign, an advocacy group. “The city would grind to a halt without transit, almost as much as it has ground to a halt with the pandemic.”
New York is obviously not alone. As cities around the world struggle to restart their economies, battered transit agencies are wrestling with how to bring riders back safely. Nearly every available option involves financial and public health trade-offs.
Running as many trains as possible to reduce crowding will strain the authority’s ability to disinfect trains as frequently as it would like. But the alternative — simply restricting the number of passengers on train cars — could hurt the city’s ability to move the masses of people needed for businesses to function.
Any strategy is complicated by the system’s sheer size and scope. In normal times, 38 percent of the public transit passenger trips in the country are on the system overseen by the authority, which runs the city’s subway and buses, two commuter rails and several bridges and tunnels.
“This is an unprecedented time and the M.T.A. is taking unprecedented action,” Patrick J. Foye, the authority’s chairman, said of the overnight shutdown. “We will follow the governor’s direction, guidance from public health experts, input from the business and labor communities, and are coordinating regionally.”
In Asia and Europe, where some cities have already reopened, public transit systems are experimenting with measures to encourage social distancing, including slashing bus capacity, introducing timed ticketing and checking riders’ temperatures.
In Paris, where more than 50 metro stations were closed as part of the city’s lockdown, officials are making face masks mandatory for riders and will limit the number of seats available on trains when the city reopens. Transit officials in London have added social-distancing markers on platforms and train cars.
The tools available to New York transit officials are more limited.
Unlike their counterparts in China, where citizens must download software onto their smartphones that dictates whether they are healthy enough to ride the subway, New York officials do not have the power to use government surveillance.
And any steps to keep riders apart and better disinfect equipment on a system with 26 subway lines and 472 subway stations will add to the transit agency’s expenses.
Crew shortages in a work force hobbled by the coronavirus will limit the authority’s ability to increase service and prevent overcrowding as riders trickle back.
Officials say that some of the responsibility for mitigating the virus’s spread will fall on riders, who must voluntarily adhere to any new guidelines, and employers, who can help prevent overcrowding during peak hours by staggering work scheduled.
“The M.T.A.’s job is to first and foremost keep the subway clean and keep it running on time,” said Joseph J. Lhota, a former deputy mayor and authority chairman. “And it’s going to be up to riders to keep a mask on and try to maintain social distancing.”
The authority has already begun to take extraordinary steps to safeguard the system.
The move to shut down the subway from 1 a.m. to 5 a.m. every night for disinfecting trains, equipment and stations is a first in the M.T.A.’s history.
Authority officials say halting service for four hours a night will allow trains to be cleaned every 24 hours by a team of about 900 cleaners. It will also provide time to test new, more efficient disinfecting technology like ultraviolet lights, microbial agents and electrostatics sprayers.
“To make sure the transit workers are safe, to make sure the riding public is safe, the best thing you can do is disinfect the whole inside of the car, as massive a challenge as that is,” Gov. Andrew M. Cuomo said at his daily briefing on Saturday.
In the weeks since the first confirmed virus cases emerged in New York, new research has made clear the risks that public transit poses for spreading infection.
A study published in the New England Journal of Medicine demonstrated that the virus can survive on steel objects, like subway poles, for three days and stay suspended in air for at least 30 minutes.
Other recent studies of the virus in China have shown that indoor, enclosed spaces — homes, restaurants and public transportation, for instance — pose a greater risk for transmission than outdoor areas.
The risk of contagion on the subway “is fairly high,” said Krystal Pollitt, an assistant professor of epidemiology at the Yale School of Public Health. “It’s an enclosed space, in most cases it’s poorly ventilated and you have very high foot traffic.”
Even so, as businesses begin to reopen and the city returns to a shade of normal, riders who have long relied on the subway will inevitably trickle back to the system.
“People have always come back to the subway, even at times when it felt like no one would ever return,” said Jaqi Cohen, campaign director for the Straphangers Campaign, an advocacy group. “I’m hopeful, even though there’s a long way to go and a lot the M.T.A. will have to do to regain the trust of riders.”
Mr. Cuomo has already ordered that riders and transit workers on crowded subway cars and buses must wear face coverings. Transit officials have also introduced rear-door boarding on buses to keep distance between riders and drivers.
But these efforts must be significantly expanded as more riders return to the system, public health experts said.
“You can’t go back to letting as many people on the subway as possible,” said Dr. Cyrus Shahpar, the director of the Prevent Epidemics program at the public health nonprofit organization Vital Strategies and a veteran of the federal Centers for Disease Control and Prevention.
In cities outside the United States, officials have introduced other steps to ensure social distancing, including cutting capacity on buses by half. In China, the rule is enforced with onboard cameras.
Most Chinese cities disinfect buses after each run, and the authorities in Hong Kong have added robots — at a cost of around $129,000 apiece — that spray hydrogen peroxide solution to disinfect train cars.
Chinese officials also dispense hand sanitizer at transit hubs — a step the M.T.A. is considering — and they have opened health-control checkpoints at stations, where riders’ temperatures are checked before they can board trains.
In Beijing, officials are testing a “subway by appointment” system, requiring riders to use a mobile app to book a time for entering the city’s two busiest subway stations during peak hours.
Still, reducing the passenger load in the early morning and late afternoon remains a major challenge.
Public health experts have said that ideally, transit systems would run as many trains as possible during busier times to reduce crowding — a strategy that in practice is limited by the number of available crews, cleaners and trains and by the prohibitive cost.
To help reduce travel during the usual 9 a.m. and 5 p.m. rush hours, major employers in Asia and Europe have brought workers back on rotating weekday schedules, provided them private transportation and temporarily housed them at hotels within walking distance of their offices.
Some of the measures could offer a template as officials and employers in New York figure out how to get the city working again, said Kathryn Wylde, the president of the Partnership for New York City, a business group.
“Employers’ first concern is that their employees feel comfortable coming back to the office, and the safety and security of the subways is the number one concern of employees,” said Ms. Wylde.
Transit advocates have also suggested that the M.T.A. should find ways to measure passenger volumes in real time — like designating transit workers to report crowding in stations — and then adjust service to add trains on the most crowded lines.
The American Public Transportation Association, a lobbying group, plans to issue detailed guidelines for transit nationwide as cities start to reopen.
“The overriding issue will be funding, having the operating dollars to do all of this,” said Paul Skoutelas, the association’s president.
The M.T.A., which has already received $3.8 billion in federal aid since the pandemic began, has asked for another $3.9 billion to offset farebox, toll and dedicated tax revenue that has effectively vanished.
The authority is also expected to incur hundreds of millions of dollars in expenses related to the virus, which will continue to mount as the city resumes some semblance of normal life.
Federal aid can help address the immediate shortfall, but regaining riders’ trust is the only way for the system to fully rebound.
“It will be a very long time, if it ever happens,’’ Danny Pearlstein, a spokesman for the Riders Alliance, an advocacy group, said, “before New Yorkers feel sanguine about packing trains during rush hour like they used to.”
Stephen Castle contributed reporting from London, and Nori Onishi from Paris.