“This is certainly a long-term fix,” Mr. Byford said. “If it were as some have suggested — if we were having a Band Aid offered to us — I for one would have rejected that.”

Under the revised plan, starting in late April, repair work would happen on nights and weekends, when one of the tunnel’s two tubes would close. But closing one tube would still be significantly disruptive for New Yorkers who rely on the L train.

“When you have only one tube in service, you may have three to four trains maximum an hour,” Dr. Horodniceanu said. “You’re going to have people who are going to wait on the platform for 20 minutes.”

The old plan, which would have closed the entire tunnel for 15 months to repair damage from Hurricane Sandy, prompted outrage in Williamsburg and other neighborhoods in Brooklyn along the L line. Some people moved away and others began to plot intricate plans to reach Manhattan.

Elected officials held a news conference on Sunday to complain about how the new plan was foisted on them without many details. Brad Hoylman, a state senator who represents a slice of Manhattan along the L line, compared the process to marrying someone you had never met.

“I kind of feel like we were planning a wedding for the last three years,” said Mr. Hoylman, a Democrat. “We get to the altar and not only does the groom run off, but you look at the guy next to you, and you’ve never seen him before."

At the same time, New Yorkers have asked why subway officials had not thought of the solution sooner. Mr. Cuomo, a Democrat in his third term, complained to reporters last week of a “transportation industrial complex,” made up of consultants and contractors, that benefit from the M.T.A. doing things the way they always have.