Seven years ago, after a series of subway failures so severe that a stretch of 2017 came to be known as the Summer of Hell, New York officials came up with a plan to make sure a crisis like that would never happen again.

Through a tolling program known as congestion pricing, they would raise enough money to restore the system to competency. This would ward off the kind of meltdowns that had left passengers stranded without service, trapped them in dark, hot cars and injured them in derailments.

Now, with congestion pricing on hold, experts warn that a return to hell is inevitable.

The tolling program would have generated $15 billion to fund critical infrastructure upgrades such as fixing century-old tunnels and crumbling tracks. Just weeks before officials were to begin collecting tolls in June, Gov. Kathy Hochul canceled the plan. In doing so, climate change and engineering experts say that she left the continent’s biggest transportation network teetering on the brink of another crisis.

“Concrete and steel, you poke holes in it, subject it to water and chemicals and salt for 100 years, it’s going to give out,” Janno Lieber, the chief executive of the Metropolitan Transportation Authority, said during a board meeting last week. “That is what’s happening, and we must do something about it.”

But the congestion pricing plan was politically unpopular, perhaps in part because the benefits to the system were harder to picture than the cost to motorists. A Siena College survey in April found that 63 percent of New York City residents were opposed to congestion pricing. It was even less popular among suburban respondents.

In other cities that have adopted congestion pricing, residents have initially reacted negatively, until the plans went into effect and their positive effects were realized.