New York City’s subway system is a maze of obstructions for people who have difficulty walking. About one out of 15 New Yorkers has an ambulatory disability, according to Census Bureau data, but the vast majority of stations lack elevators and ramps, making much of the city hard to access for the hundreds of thousands of residents who rely on them.

New York has lagged far behind other major American cities in building access points for people with disabilities. Upgrading the entire subway — the continent’s biggest transit network — will take decades and cost billions of dollars. And promises from the M.T.A. with long and uncertain timelines have diminished many disabled riders’ faith in the authority’s ability to deliver.

“I’ll believe it when I see it,” said Yimbert Remigio, 24, who lives in the Bronx and has always relied on a wheelchair.

Today, only 27 percent of the system’s 472 stations are considered accessible under the Americans with Disabilities Act, meaning they can accommodate riders with a range of disabilities and can be navigated without climbing stairs.

The authority promised last year to add elevators and ramps to 95 percent of stations by 2055 as part of a settlement agreement in two class-action lawsuits over the issue. And its latest capital plan, which was approved at the start of 2020 and sets construction priorities through next year, called for making 67 more stations A.D.A. accessible.

But so far, the needed upgrades have been completed at just two of those stations. Elevators or ramps are being built at 20 more, but work is not set to be completed until the end of 2026. There is no timeline for when construction will begin at the remaining 45 stations, the authority said.

“Many of us won’t be here in 2055,” said Sasha Blair-Goldensohn, a software engineer at Google and a disability advocate who was partially paralyzed after a rotted tree branch fell on him in Central Park 14 years ago.

“The number of wheelchair users you see on the subway is way, way less than the number who would use it if stations all had working elevators,” he added.

Tim Mulligan, who oversees the authority’s capital programs, stressed that the agency was completing many other elevator and ramp expansion projects outside the current plan, adding up to upgrades at a total of 81 stations.

“The pace of construction awards for A.D.A. is five times what the pre-2020 pace of A.D.A. station awards are,” Mr. Mulligan said, referring to contracts for upgrade projects. “Once that contract is awarded, the station gets built. Period.”

A New York Times analysis in 2019 found that there were 550,000 people in the city who had difficulty walking, and that two-thirds of them lived far from an accessible subway station. At the time, that meant about 4 percent of New York’s 8.3 million residents were largely unable to ride.

The Bronx has some of the highest concentrations of these residents — more than 122,000 — but only 15 of the borough’s 70 stations are accessible. Ten more are set to be upgraded under the current capital plan, including one at East 149th Street on the 6 line, where elevators are set to open in late September, delayed from a previous July target.

Several more elevators are planned along that line, near Mr. Remigio’s home in Mott Haven.

Currently, only one of the nine stations within a mile of his home can accommodate his chair, so he mostly gets around by bus.

To commute to a summer internship on West 168th Street in Manhattan, he first had to take a bus south to an accessible station in Harlem before heading north again.

He would board using a ramp, which could not be rolled out if parked cars were blocking the curb. If the bus was too crowded to fit his wheelchair, he would have to wait for another.

Wheelchair users and advocates for people with disabilities have long urged the M.T.A. to work faster to make the system more navigable, often packing public meetings to confront transit leaders with their frustrations.

M.T.A. officials said the authority was working as fast as it could without drastically interrupting service for millions of riders. To build safely, crews must shut down sections of the subway, said Quemuel Arroyo, who oversees accessibility efforts for the M.T.A.

“Everybody wants it done faster, but not at the expense of their commute,” Mr. Arroyo said. “There’s only two things that New Yorkers really hate: the status quo and change.”

Transit experts and advocates say that making the system more equitable is not only a moral imperative, but also a crucial step to saving it from a crisis of diminished ridership.

Bringing New Yorkers with disabilities — as well as tourists and other visitors with accessibility challenges — onto the subway could increase fare revenue for the system, which has yet to fully rebound to prepandemic levels.

“In order for the M.T.A. to be financially viable, it is going to continue to depend on its ridership,” said Lisa Daglian, executive director of the transit authority’s Permanent Citizens Advisory Committee, a watchdog group. “And ridership needs to be able to get into and out of the system.”

Jessica Hsieh, 33, who uses a wheelchair and lives in Queens, where she works at a nonprofit organization, said “it would just mean the world” if the subway had more working elevators.

“Most definitely, one of my biggest challenges is memorizing the stops that are wheelchair accessible,” Ms. Hsieh said. “You’ve got to have a Plan A and a Plan B.”

One day about 12 years ago when the 7 train was not running its usual route, Ms. Hsieh said she became stuck at Queens Plaza station while seeking an alternate path. Six police officers carried her motorized wheelchair downstairs so that she could get home.

Ms. Hsieh said the system had become easier to navigate.

Many riders with disabilities and advocates have urged the M.T.A. to more diligently repair existing elevators, which the agency says are maintained at a rate of roughly 97 percent.

But a report put together by two City Council members found that 7 percent of elevators were marked as “out of service” on the M.T.A. elevator status page on sample days last January.

The report also found that elevators maintained by third parties were out of service three days longer, on average, than those managed by the M.T.A.

Tamara Morgan, 38, a wheelchair user who lives in Queens and commutes to work in Manhattan, said that if the system were easier to navigate, she would be able to visit her family in Brooklyn more often.

Much of her life is dictated by the state of the transit system’s accessibility features. She lamented that while planning to attend a friend’s wedding on Long Island earlier this summer, she and other guests who use wheelchairs felt worried about arriving at the venue on time and without incident.

“It’s a celebratory, joyous moment,” Ms. Morgan said. “We’re worrying about, like, ‘Can we get there safely?’”

When Mr. Remigio does take the train, he allots at least an extra half-hour of travel time to account for elevator downtime and delays.

He recalled traveling to a job interview at City Hall on a day when the elevator at Fulton Street was out of service. He had to bypass the station, change to a train going in the other direction, ride until he reached a station with a working elevator, and roll his wheelchair to the interview from there.

Despite the obstacles he faces navigating public transit, Mr. Remigio said he loved New York and could not imagine living elsewhere.

“In a perfect world, I could get around the city just like anybody else,” he said. “There wouldn’t be so many hoops that I would have to jump through.”