As governor, Mr. Cuomo controls the M.T.A., and he has done far too little for it. In recent months, the criticism of his management has increased along with the breakdowns, delays and other indignities suffered by the system’s hapless users. But this week, he accurately diagnosed many of the problems and pledged to fix them. He also announced a contest to seek ideas for improving the system, a seductive ploy but nowhere near what he has to do if he’s truly serious.

His No. 1 task is to appoint a capable and credible new leader for the authority, which has been without a permanent chairman and chief executive since Thomas Prendergast announced his retirement in January. The governor will have to act fast, because whomever he names has to be approved by the New York Senate, which adjourns next month. That person, in turn, will need to devise a detailed plan to make the system more reliable and increase its capacity while maintaining safety over the next decade. With Mr. Cuomo’s help, the new executive will also have to come up with ways to pay for all this good stuff, which may be the hardest part of all.

There’s no mystery about what has to be done, beginning with a major investment in the subway’s antique signaling system, which dates to the 1930s. It is a major cause of delays and the main reason officials cannot add trains to busy lines. The M.T.A. has installed a modern, communications-based signaling system on the L line, and the No. 7 line will have one this year. But at this rate, it could take a half-century to update all lines. There has to be a way to greatly speed up that process, even if that means taking subway lines out of service for months at a time.

New signals will not be enough. The authority also needs to more quickly replace its trains, some of which are a half-century old. Mr. Cuomo has complained that it takes three years for the authority to get new trains once they are ordered. Experts say time could be saved if the M.T.A. simply did without some customized features, like doors that slide into pockets. Other transit agencies buy trains in which doors slide across the outside of cars.

In the shorter term, the M.T.A. can make bus service a more appealing alternative to subways. Working with the city, it could add more dedicated bus lanes and install systems that give buses priority at traffic signals: changes that have already helped speed up buses on some routes. It could also add more buses that riders can board from any door, reducing wait times.